1V1€SI_J RETURNING MATERIALS: P1ace in book drop to LJBRARJES remove this checkout from Jun—(gun... your record. FINES wi11 be charged if book is returned after the date stamped be1ow. 5:533 .4173; NUCLEAR MAGNETIC RESONANCE AND MASS SPECTROSCOPY STUDY OF SOME MACROCYCLIC COMPLEXES By Yang-Chih Lee A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Chemistry 1983 a: v u 'c c C. . A; r. r _ ‘1‘ i . g 4 Y. 2,. . . » ... 1 . 1 . V1. «Wk .1 /¥r;1-_’:‘5"¥/r ABSTRACT NUCLEAR MAGNETIC RESONANCE AND MASS SPECTROSCOPY STUDY OF SOME MACROCYCLIC COMPLEXES By Yang—Chih Lee The complexation of the Tl+ ion by 1806 and its analogs in various solvents has been studied by 205T1 NMR. The results show that the stability constants of five complexes in different solvents generally decrease with increasing Gutmann donor number in the order: nitromethane > aceto- nitrile > acetone > sulfolane > dimethylformamide > water > dimethylsulfoxide > hexamethylphosphoramide. Also, the com- Plexing strength of different ligands with the T1+ ion gen- erally decreases in the order DA1806 > 1806 > cis-syn-cis- DC1806 > DBl8C6 > DTlBCé. Proton and carbon-13 NMR spectra indicate that the conformation changes occur during complexa- tion for DT1806. + . Thermodynamic parameters of the T1 ion complexed by A~', $vVU’ cr‘rmv Vbov. v. 7 . I uh. . x V A... I s 7 u o .- H . a x 2. a: .ru 2 up. n, v .7. 1 § e1 5.. S r” . n e . . .C e e. r. e A v 2 . r . AD Cu .. .u :C Ce V“ 3. -b if” . a o b a: u. . Yin Ab» cl .rts .. . WW vL. : ¢ men .. J c. . Y e A ”Y N ‘v" ‘1" 5“ ”Car ~,"~ n9 ‘ Yang-Chih Lee 1806, DB1806 and DT1806 indicate that these complexation reactions are generally enthalpy stabilized (AH: < 0) but entrOpy destabilized (As: < O). The solvation of the Tl+ ion in several low and high solvating power mixed solvents has been studied. A good correletion was observed between the iso-solvation point and the donor number of the solvent which indicate that the donicity of a solvent is more im- portant than its dielectric constant scale in determining its relative solvating ability. Complex formation of the T1+ ion with DA1806 or DT1806 was investigated in DMF/HZO or DMF/AN mixed solvents respec- tively. The formation constant, Kf, increases with increas- ing amounts of dimethylformamide and acetonitrile in the respective binary mixtures. Mass spectra of 1204, 1505, 1806 and 2107 were inten- sively studied. According to the results, the fragmentation mechanisms of these macrocycles were developed and a linear intermediate was proposed. The mass spectra of two linear pOlyethers were taken at 70 eV and ion abundances as a function of electron energy for 1806 were used to verify the Preposed fragmentation pathways. To My Wife and My Parents ii I flier“ v- F5" 4‘..v‘v .. as. .0. ~~..I-AI OF - . u . a 1.. u. \ l . . . 4| ...u +¥ -Kv Q a Anfl“ r~v “NV MW ‘ . . . . u . -. A. a . v . «\~ .1 t e . e .s Lev ». .. Z. A w W. in F2.» on u .uls obs «xy .9 . :5 a; av .fi‘ . v. RU .‘v .1 NJ L. “a. a. . 2,— L b u t h. I «\v A v ACKNOWLEDGEMENTS The author wishes to express his sincere gratitute to Professors Alexander I. Popov and John Allison for their continual guidance, encouragement, and invaluable assis- tance throughout this study. Professor 0. H. Brubaker, 0. K. Chang and Dr. K. Hallenga are also acknowledged for their helpful discussions. Financial aids from the Department of Chemistry, Michigan State University, the National Science Foundation, and Dow Chemical Company are also acknowledged. Special thanks are also extended to the members of the research groups of both Professors Popov and Allison for their discussion and friendship. Many thanks go to Mr. Tom Clarke, and Mr. Kermit Johnson, for their maintenance of the NMR spectrometers. Also, thanks are given to Mro Brian Musselman and Miss Betty Baltzer of the NIH-MSU Mass Spectrometry Facility for assistance in obtaining reliable mass spectra. Above all, the author wishes to thank his family and his wife's family for their unending encouragement and support. Finally, my sincere thanks to my wife, Bi-zu. for her love, patience and unending encouragement throughout this study. To them and my daughters, Chai-zon and Jenny, I dedicate this thesis. iii ... 3.. . . ”U I ~ Ir .‘C _-v a...‘ gov , up U... Chapter TABLE OF CONTENTS LI ST OF TABLES I I I I I I I I I I I I I O I I LIST OF FIGURES I I I I I I I I I I I I I I I PART I - NUCLEAR MAGNETIC RESONANCE STUDY OF SOME MACROCYCLIC COMPLEXES . . . . CHAPTER I - INTRODUCTION AND HISTORICAL . . . Introduction I I I I I I I I I I I I I I I Historical Review. . . . . . . . . . . . . A. Neutral Macrocycles. . . . . . . . B. Macrocyclic Polyethers and Their Complexes in the Solid State . . . 0. Complexation of 18-0rown-6 and Its Substituted Analogs in Solution. . D. Effect of Solvent on the Stability of Macrocyclic Complexes . . . . . E. Thallium-205 NMR Measurement . . . II " EXPERIMENTAL. I o o o o o o o o o Salts and Ligands Purification . . . . Solvent Purification . . . . . . . . . Sample Preparation . . . . . . . . . . Instrumental Measurements. . . . . . . A. B. C. Thallium-ZOS and Lithium-7 NMR . . Chemical Shift Reference and Correction . . . . . . . . . . . . Proton and Carbon-13 NMR . . . . . iv Page viii xii KnUxNi—‘l—J 13 35 38 42 43 A5 A6 A7 A7 52 54 V. In." C ‘J ‘... .— VJJI» . an. Ft. h‘yw ‘ge Chapter Page D. Data Handling . . . . . . . . . . . . . . . 54 CHAPTER III - COMPLEXATION OF THALLIUM(I) STUDY BY l8-CROWN-6 AND ITS SUBSTITUTED ANALOGS IN VARIOUS SOLVENTS. . . . . . . . . . . . . 57 1. Introduction . . . . . . . . . . . . . . . . . 58 2. Selection of External Reference Solution for Thallium-205 NMR . . . . . . . . . 59 3. Results and Discussion. . . . . . . . . . . . . 63 A. Complexation of the T1+ Ion by DB1806 . . . 63 B. Complexation of the T1+ Ion by 0is-Syn-Cis-D018C6 . . . . . . . . . . . . 75 0. Complexation of the Tl+ Ion by 1806 . . . . 79 D. Complexation of the T1+ Ion by DA1806 . . . 86 E. Complexation of the Tl+ Ion by DT1806 . . . 92 F. Comparison of the Results . . . . . . . . . 96 CHAPTER IV - THERMODYNAMIC STUDIES OF THALLIUM(I) SALTS WITH lB-CROWN-6 AND ITS SUBSTITUTED ANALOGS IN SEVERAL SOLVENTS I I I I I I I I I I I I I I I I 106 lI Introduction I I I I I I I I I I I I I I I I 107 2. Thermodynamic Study of the Complexation of the T1+ Ion by 1806 . . . . . . . . . . . 107 3. Thermodynamic Study for the Complexation of the T1 Cation by DBl806 . . . . . . . . . 118 4. Thermodynamic Study for the Complexation of the T1 Cation by'DT1806 . . . . . . . . . . 126 5. Comparison of the Thermodynamic Parameters . . 132 CHAPTER v - THALLIUM-205 NMR STUDY OF THE IONIC SOLVATION AND COMPLEXATION or THALLIUM(I) ION IN MIXED NONAQUEOUS SOLVENTS . . . . . . . . . . . . . . . . 136 A; v.5." OP '9“ V‘ Chapter CHAPTER 1. Page Introduction . . . . . . . . . . . . . . . . . 137 Preferential Solvation of the Thallium(I) Ion in Mixed Solvents. . . . . . . 138 Complexation of the Tl+ Ion by DA1806 or DT1806 in Mixed Solvents . . . . . . . . . 152 VI "' MISCELLANEOUS o o o o o o c o o o o o o 161‘; Complexes of l8-Crown-6 and Its Analogs Studied by Proton and Carbon-l3 NMR . . . . . 165 Ion Pair Formation Studies of Lithium Perchlorate and Lithium Chloride in sulfOlane I I I I I I I I I I I I I I I I I I 191 - MASS SPECTROMETRY STUDIES OF CYCLIC AND LINEAR POLYETHERS. . . . . . . . . . . . 195 IntrOduC-tion I I I I I I I I I I I I I I I I I 196 Historical Review. . . . . . . . . . . . . . . 197 A. Electron Impact Mass Spectra . . . . . . . 197 B. The Mass Spectra of Crown Ethers . . . . . 202 Experimental . . . . . . . . . . . . . . . . . 206 A. Reagent Purification . . . . . . . . . . . 206 B. Sample Preparation . . . . . . . . . . . . 206 C. Instrumentation . . . . . . . . . . . . . 207 Results and Discussion . . . . . . . . . . . . 208 A. Mass Spectra of Unsubstituted Crown Ethers . . . . . . . . . . . . . . . 208 B. Mass Spectra of Unsubstituted Crown Ethers at High Sample Pressure . . . 220 0. Mass Spectra of l8-crown-6 at Different Electron Energies. . . . . . . . 224 D. Mass Spectra of Some Linear Polyethers . . . . . . . . . . . . . . 235 vi ‘. “rcr‘ er U4...» . v. . K.I\ (O Ig-rgog- ”ya I." upon-odd; J... .U-0 p.- .o.._.‘ -1- 1.1.. _., u- .— .u.._' I'"" °“ s. H.» "u_ N‘. 0,“ u. Chapter Page 5. Suggestions for Further Studies . . . . . . . 241 APPENDICES APPENDIX 1 - THE SIGN CONVENTION FOR NMR SPECTRA . . . . . . . . . . . . 244 APPENDIX 2 - DETERMINATION OF COMPLEX FORMATION CONSTANTS BY THE NMR TECHNIQUE: DESCRIPTION OF THE COMPUTER PROGRAM KINFIT AND SUBROUTINE EQUATIONSo . . 248 A. Determination of Formation Constants for a 1:1 complex . . . . . . . 248 B. Determination of Formation Constants for 1:1 and 2:1 complex I I I I I I I I I I I I I I I I I 252 APPENDIX 3 - DETERMINATION OF ION-PAIR FORMATION CONSTANTS BY THE NMR TECHNIQUE; DESCRIPTION OF THE COMPUTER PROGRAM KINFIT AND SUBROUTINE EQUATION . . . . . . . . . 256 REFERENCE I I I I 0 0 I I I I I I I I I I I I I I I I 260 vii ¢ Table 10. ll. 12. 13. LIST OF TABLES Diameter in A of Selected Macrocyclic Ethers and Cations . . . . . . . . . . . Cations Selectivities of Several Neutral Ionophores in Solution . . . . Stability Constants of Mn+-l806 Complexes. . . . . . . . . . . . . . . . Stability Constants of Mn+eDBlsco Complexes. . . . . . . . . . . . . . . . Stability Constants of Mn+-D018C6 complexes I I I I I I I I I I I I I I I I Thermodynamics of Mn+-Aza-or-Thia- Substituted Polyethers in Aqueous SOlutiOn at 25 C I I I I I I I I I I I I Stability Constants of Mn+-DA18C6 or- DT18C6 Complex . . . . . . . . . . . . . Nuclear Properties of Alkali and Thallium Elements. . . . . . . . . . . . Key Solvent Properties and Correc- tion for Diamagnetic Susceptibility on the Varian DA-60 and on the Bruker WWI-250 I I I I I I I I I I I I I I I I I Thallium-205 Chemical Shiftsoof Thal- . lium(I) Salts in Water at 25 C . . . . . Dependance of the Tl-205 Chemical Shifts on DB1806/T10104 (0.01 M) in Various SOlven-ts I I I I I I I I I I I I I I I I Stability Constants and Limiting Chem- ical Shifts of (DB18C6-T1) and (cis- syn-cis-D018060Tl) in Various Solvents. The Variation of 205T1 Chemical Shifts with DB18C6/T10104 (0.004 M) in Acetone (SW:lOOOHZ) I I I I I I I I I I I I I I I viii Page l4 l6 18 21 27 29 39 55 61 65 71 72 ‘ ', Lacie «i. :2 a.— ‘1... nu] «1.1 ~>« Ac ac AC Ania A/\ ”C Table Page 1“. Dependance of 205T1 Chemical Shifts on cis—syn—cis-DC1806/ T1010 (0.01 M) in Various SOlve t8 0 o o o I o o o o I o o o o o o o o 76 15. The Variation of 205T1 Chemical Shifts with 1806/T1C10 (0.01 M) MOle Ratio in SF and H PA I I I I I I I I I I 81- 16. Stability Constant and Limiting Chemical Sh'fts of (18C6-Tl):. (DA1806-Tl) and (DT1806.T1) in Various Solvents . . . . . . . . . . . . . . 83 17. The Variation of 130 Chemical Shifts with Tit/1806 (0.0u M) in DMF with AN-d3 as Reference . . . . . . . . . . . . . 8A 18. Thallium-205 Chemical Shifts Ratio Data for 0.01 M T1010 Complex with DA18C6 in Varigus Solvents at 24°C . . . . . . . . . . . . . . 87 19. Thallium-205 Chemical Shift-Mole Ratio Data for 0.01 M TlClO Complex with DA1806 in H20 3t 2400 . . . . . 89 20. Thallium-205 Chemical Shift-Mole Ratio Data for 0.01 M TlClO Complex with DT18C6 in Varigus Solvents at 24°C . . . . . . . . . . . . . . 93 21. Stability Constants of the Thal- lium(I) Complexes in Various Solvents. . . . . . . . . . . . . . . . . . . 97 22. Thallium-205 Chemical Shift-Mole Ratio Data for 0.01 M T1010“ Complex with 1806 in SF at Various Temperatures . . . . . . . . . . . . 109 23. Thallium-205 Chemical Shift-Mole Ratio Data for 0.01 M T1010“ Complex with 1806 in DMF at Various Temperatures . . . . . . . . . . . . , , , , 111 24. Temperature Dependance of the Formation Constants and Limiting Chemical Shifts of (1806-Tl)+ Complex in SF and DMF . . . . . . . . . . . . 116 1X 4.1. n/L /.Fu nx~ 3; Any n1 r7. Ax~ Table Page 25. Thallium-205 Chemical Shift-Mole Ratio Data for 0.01 M T1C10 Complex with DB1806 in SF at Various Temperatures . . . . . . . . . . . . 119 26. Thallium-205 Chemical Shift-Mole Ratio Data for 0.01 M T1C10 Complex with DB1806 in DMF gt Various Temperatures . . . . . . . . . . . . 121 27. Temperature Dependance of the Formation Constants and Limiting Chemical Shifts of (DB1806- T1)+ Complex in SF and DMF. . . . . . . . . . . . 125 28. Mole Ratio-Chemical Shift Data for T1010 (0.01 M) in the Presence of DTlBCg in AC at Different Tempera- tureSI I I I I I I I I I I I I I I I I I I I 127 29. Thallium-205 Chemical Shift-Mole Ratio Data for 0.01 M T1010 Complex with DTl8C6 in SF at Various Temperatures . . . . . . . . . . . . 128 30. Temperature Dependence of the Formation Constants and Limiting Chemical Shifts of (DT1806 Tl)+ complex in AC and SF 0 o o o o o o o o o o o 133 31. Thallium-205 Chemical Shifts of T1010“ in Mixed Solvents . . . . . . . . . . 139 32. Preferential Solvation Data of Several Binery Solvent Systems . . . . . . . . . . . 150 33. The Gutmann Donor Number and Dielectric Constant of Several Solvents . . . . . . . . 150 34. Mole Ratio-Chemical Shift Data for DA18C6/T1010 (0.01 g) in DMF/H2 0 Mixed Solven s at 24 C . . . . . . . . . . . 154 35. Mole Ratio-Chemical Shift Data for T10104 (0.01 M) in the Presence ofODT1806 in AN/DMF Mixed Solvents at 24 C. . . . . . . . 156 Table 36. 37I 38. 39. 40. 41. 42. 43. 4L». 45. 46. 47. 48. Page Log of Formation Constants and Limiting Chemical Shifts for (DA1806-Tl)+ and (DTl8co-Tl)+ Complexes in Mixed Solvents. . . . . . . . 161 Carbon-l3 Chemical Shift-mole Ratio Data for 1806 Complex with Cation in AN-d3 Solution . . . . . . . . . . . . 168 Carbon-13 Chemical-Mole Ratio Data for DB18C6 Complex with T1C104 in DMF and DMSO . . . . . . . . . . . . . 170 Carbon—13 Chemical Shift-Mole Ratio Data for DA18C6 Complex with Cation in AN with Me0D as Reference . . . . . . . 172 Carbon-13 Chemical Shift-Mole Ratio Data for DTl8C6 Complex with Various Cations in AN or AC with Me0D as Reference I I I I I I I I I I I I I I I I 175 Proton Chemical Shift-Mole Ratio Data for 1806 Complex with Various cations in AN-d3 I I o I I I I I I I I I I 178 Proton NMR Parameters of DTl8C6 and Its Complexes. . . . . . . . . . . . . . . 181 Proton NMR Parameters of DA1806 and Its Complexes . . . . . . . . . . . . . . 190 Lithium—7 Chemical Shift—Concentration Data for LiClOu and LiCl in Sufolane at 31 C I I I I I I I I I I I I I I I I I I 193 Principal Fragment Ions in the 70 eV Mass Spectra of Crown Ethers . . . . . . . 210 Principal Fragment Ions in the 70 eV Mass Spectra at High Sample Pressure of Crown Ethers . . . . . . . . . . . . . 222 Principal Fragment Ions in the 10-100 eV Mass Spectra of 18-crown-6. . . . . . . 228 Principal Fragment Ions in 70 eV Mass Spectra of Linear Polyether . . . . . . . 237 xi .a. T: 1. :. Figure 10. 11. 12. LIST OF FIGURES Structures of some naturally occuring and of some synthetic macrocyclic compounds . . . . . . . Crystalline structure of (IiSCN'l8C6) I I I I I I I I I I I I Three—dimensional crown complex Of (KI'DBBOClO) I I I I I I I I I I Crown complex of (2KSCN-DB2408) . . Sandwich structure of (K+-2Bl5C5). The structure of dibenzo-l8-crown-6 complex with RbSCN. . . . . . . . . The structure of crown complex of (K.DA1806)I I I I I I I I I I I I I The structure of the (PdCl oDTl8C6) complex (the Pd coordinate to two chloro ligand and two sulfur atoms of thia ether) . . . . . . . . . . The isomers of DClBC6 . . . . . . . The mirror images obtained from a real line S as a result of Fourier transformation. . . . . . . Free induction decay for a set of identical nuclei with Lamor frequency, VS, excited by a pulse of frequency exactly equal to Vs . . . . . . . . The real and ima inary NMR 3 ectra of % acetate (A and 0.3 M thallium(I) nitrate (B) on DA-60 Spec- trometer (SY: syn—thesizer frequency, RF: resonance frequency, SW: 25000 Hz). 1.5 M thallium(I xii Page 10 10 12 12 24 24 33 33 49 49 51 l4- 1. Q. a g 2. 1 iii A/ .- a. C. a/\ Figure 13. l4. 15. l6. 17. 18. 19. 20. 21. 22. 23. 24. Thallium-205 chemical Shifts vs. thallium(I) salt concentration in water at 2500 (0. 3 M TlN03 )in H20 as reference) . . . . . . . . . . Thallium-205 chemical shifts vs. DB18C6/Tl mole ratio in various temperatures . . . . . . . . . . . . Chemical shifts of Tl-205 vs. DB18C6/Tl (0.004 m) mole ratio in acetone . . . . . . . . . . . . Chemical Shifts of T1+205 Ls. the cis- syn- -cis-DCl8C6/Tl mole —ratio in various solvents . . . . . . . . . Chemical shifts of Tl-205 vs. 1806/Tl+ mole ratio in various solvents. . . . Chemical shifts of 0- ~13 LS. Tl +/ 1806 (0.04 M) mole ratio in dimethylformamide . . . . . . . . . . Chemical shifts of T1-205 LS. DA1806/Tl+ mole ratio in various solvents . . . . . . . . . . . . . . Thallium- -205 chemical Shifts 1s. DTl8C6/T1+ Mole ratio in various solvents . . . . . . . . . . . . . . Thallium-205+chemical shifts of solvented Tl ion and the limiting chemical shifts of (Tl-Crown) complexes . . . . . . . . . . . . . . Thallium-205 NMR Spectra of different linewidths. . . . . . . . . Chemical Shifts of T1- -205 vs. 1806/ T1010 (0. 01 M) mole ratio in sul— folan at different temperatures . . Chemical shifts of205Tl vs. 1806/ T1010“ (0.01 M) mole ratio in DMF at various temperatures . . . . . . . xiii Page 62 67 73 78 82 85 9O 95 101 104 113 115 v. .4 f: . :4 fhv a/L h/L aq/ AC «.1; ace RJ «.3 .JJ .41. Figure Page 25. Chemical shifts of T1- 205 Ls. ' DB18C6/Tl+ (0. 01 M) mole ratio in DMF at various temperatures . . . . . . . . . 123 26. Chemical shifts of T1- 205 vs. DB18C6/Tl+ (0. 01 M) mole ratio in SF at various temperatures . . . . . . . . 124 27. Chemical Shifts of 205T1 Kg. DT1806/T1+ (0.01 M) mole ratio in A0 at different temperatures. . ... . . . . 130 28. Chemical shifts of 20511 is, DT1806/Tl+ (0.01 m) mole ratio in SF at different temperatures. . . . . . . . 131 29. Aplot of ln K vs. l/T for the com- plexation of the T1 ion with 1806 and its analogs I I I I I I I I I I I I I I 134 205T 30. Chemical shifts of 1 vs. mole % of NM or PC in NM/DMSO or PC/DMSO mixed solvents (0.005 M T1010“) . , . . . . 141 31. Thallium- 205 chemical shifts vs. mole % of AN or THF in AN/DMSO or THF/DMSO mixed solvents . . . . . . . . . . 142 32. Thallium- 205 chemical shifts vs. mole % of AN or H 0 in AN/DMF— or HO/DMF mixed solgents (0. 01 M TiClOLL) I I I I I I I I I I I I I I I I I I 143 33. Chemical shifts of 205T1 vs. mole % of DMF or HMPA in DMF/DMSO or HMPA/ , DMSO mixed solvents (o. 01 M T1010“) . . . . 14+ 34. Thallium- 205 chemical Shifts vs. mole % of AN in AN/DMSO mixed— SOlventS I I I I I I I I I I I I I I I I I 147 35. The plot of Gutmann donor number Ls. iso- solvation point in several DMSO binary mixtures with other solvents . . . . 151 36. Thallium- 205 chemical shifts Ls. DA1806/T1010 (0. 01 M) mole ratio in DMF/H20 s stems. . . . . . . . . . . . . 158 xiv _u/ A.) I». Figure 37- 38. Chemical shifts of T1— 205 vs. mole ratio of (DT1806)/(Tl+) in DMF/AN mixed solvents . . . . . . . . . Log of stability constants of Page 159 (DT1806 Tl)+ and (DTl8C6 Tl)+ complexes yg. solvent com o- sition in DMF/AN and H 0 DMF mixed solvents . . . .2. . . . . . . . . . . 163 39. Carbon-l3 NMR Spectra of 1806 (0.02 M) in AN-d3 with Me0D as reference. . . . . . . . . . . . . . . . . . 166 40. Carbon—l3 NMR spectra of DB1806 (0.04 M) in DMF with AN- -d3 as reference. . . . . . . . . . . . . . . . 169 41. Carbon-l3 NMR spectra of DA1806 (0.04 M) in AN with AC— —d6 as reference. . . . . . . . . . . . . . . . 171 42. Carbon-l3 NMR spectra of DT1806 (0.04 M) in AN with Me0D as reference I I I I I I I I I I I I I I I I I I 1 74 43. Proton NMR spectra of DT1806 (OI02 M) in AN_d3 I I I I I I I I I I I I I 179 KPF6 44. Proton NMR spectra of 1.01 in AN- -d3. . . . . mlBCg: . . . . . . . 180 45. Proton NMR spectra of (DT1806Ag)+ complex in AN-d3 . . . . . . . . . . . . . . 182 46. Proton NMR spectra of (DT1806Ag)+ complex after treating with gaussian multiplication . . . . . . . . . . . . . . 183 47. Proton NMR spectra of proton l and 2 in (DT1806 Ag)+ complex after treating with gaussian multiplication . . . . . . . . 185 48. The simulative proton NMR spectra (AA' XX' system) of (DT1806. Ag)+ complex . . . . . . . . . . . . . . . . . 186 XV Figure 49. 50. 51. 52. 53. 54. 55- 56. 57I 58. 59- 60. 61. 62. Proton NMR spectra of DA1806 (0.02 M) after treating with gaussian multiplication . . . . . . . . . . Lithium-7 chemical shifts gs. concentration of LiCl and LiClO4 . . . . . Electron impact ionization of the molecule AB (an excited state is indicated by *) . . . . . . . . . . . . . . The pathways of electron impact decomposition for gas phase molecules . . . . . . . . . . . . . . . The 70 eV mass spectra of (a) 1204 (b) 1505 (c) 1806 (d) 2107 . . . . . . Fragmentation scheme for crown ethers I I I I I I I I I I I I I I I I I The formation of protonated 12- crown-4 and protonated 9-crown-3 from 18-crown-6 via a linear intermediate . . . . . . . . . . . . . . Fragmentation of lZ-crown-4 to from pI‘OtOnated 9-CI‘OWI1-3 o c o 0 o o o u The dissociation of protonated 9-CI‘OWH-3 O o o o o o o o o o o o o o o o o The mass spectra of 1806 at various electron energies (12-18 8V) 0 o o o o o o o o o o o o o The mass spectra of 1806 at various electron energies (20-50 eV). . . . . . The mass spectra of 1806 at various electron energies (60-100 eV) . . . . . Ion abundance (% of total ionization) as a function of electron energy (in 8V) I o o o o o o o o o o o o o c o o 0 Ion abundances (% of total ionization) as a function of electron energy (in eV) for 1806. I I I I I I I I I I I I xvi Page 189 192 200 203 209 213 215 217 219 225 226 227 233 234 Figure Page 63. The 70 eV mass spectra of tetra— ethylene glycol dimethylether and triethylene glycol dimethylether . . . . . 236 64. Fragmentation of 4-EGDME . . . . . . . . . 239 65. Fragmentation of 4—EGDME and 3—EGDME to form protonated crow]. ether I I I I I I I I I I I I I I I 240 66. The sign convention for NMR spectum . . . . 247 xvii l. 2. LIGANDS 3—EGDME 4-EGDME 12C4 l5C5 18C6 21C? DA1806 DT1806 DC18C6 DB18C6 SOLVENTS AN AC NM SF PY PC DMF THF DMSO HMPA LIST OF ABBREVIATIONS Trienthylene glycol dimethyl ether Tetraethylene glycol dimethyl ether lZ-crown-4 15-crown-5 18-crown-6 21-crown-7 Diaza-18-crown-6 Dithia-lB-crown-6 Dicyclohexyl-lB-crown-6 Dibenzo—18-crown-7 Acetonitrile Acetone Nitromethane Sulfolane Pyridine Propylene carbonate Dimethylformamide Tetrahydrofuran Dimethylsulfoxide Hexamethylphosphoramide xviii PART I NUCLEAR MAGNETIC RESONANCE STUDY OF SOME MACROCYCLIC COMPLEXES CHAPT ER I INTRODUCTI ON AND HIST ORICAL I"-.- 1-.."- ’ N ”...-...- 4. r4 1L :‘ ‘4 “Legs. {« 1.4.18 S '- In“ , wu‘r‘ r"J~v.‘E‘ ‘V U ‘. r w. ‘J‘CTC'N'I' ~ t “an 3r ‘°.. *c: ‘I 0 v.CO:e i INTRODUCTION The beginning of macrocyclic polyether chemistry generally dates to Pedersen's first paper published in 1967 (l), where he reported the synthesis of 33 macrocycles and their potential as complexing agents for the alkali ions. Since then, the complexation reactions of macrocyclic polyethers with alkali and alkaline earth ions have been studied extensively and some comprehensive reviews on the subject are available (2-9). For macrocyclic crowns smaller than l8-crown-6, rela- tively few studies have been reported. In the case of l5-crown-5 (10), results show almost no alkali cation selectivity in aqueous solution, which is consistent with its cavity being too small for most alkali cations. For benzo-l5-crown-5 and cyclohexo-lS-crown-5 (11,12), selec- tivities are difficult to distinguish because of the for- mation of 2:l complexes if the cation is larger than the ligand cavity. For crowns larger than 18-crown-6 which are too large for most cations in the alkali or alkaline earth series (Table l) cavity size of the crown ether does not appear to be the major factor in determining selectivity. Other factors become increasingly important (11.13.14). It may be con- cluded that, for macrocyclic polyethers, correlation of - CT $17.17.- A , F! GA; ~71 *T'r ‘1. me» 'o Aw‘ “ selectivity with cavity size is restricted essentially to 18-crown-6 and its substituted analogs. Thallium-205 NMR is a good probe for studies of the role of potassium ions in biological systems (15) since the size and the prOperties of the two ions are very similar. Complexes of the Tl+ ion with l8-crown-6 and its substituted analogs (Figure l) in various solvents can be used in separation chemistry and can also be used as a model for the investigation of the transport reaction of potassium ions across some biological membrane. This dissertation is divided into two parts. Nuclear magnetic resonance and mass spectrometry studies are pre- sented in Parts I and II respectively. Complexation reac- tions and thermodynamic studies of the Tl+ ion with 1806, DB18C6, DClBC6, DAl8C6 and DT1806 in various solvents have been studied and are discussed in Chapters III and IV of Part I respectively. Also preferential solvation effects on the thallium(I) ion and thallium(I)-crown complex in mixed solvent systems are described in Chapter V of Part I. In order to investigate ion-molecule reactions involving metal ions and macrocyclic polyethers in the absence of solvent, mass spectra of triethylene glycol dimethylether, tetraethylene glycol dimethylether, 12-crown-4, l5-crown-5, 18-crown-6 and 21-crown-7 were intensively studied. The fragmentation patterns for non-substituted macrocycles and of their linear analogs are prOposed in Part II. WW. 10’1me 11' ~R'-R’-R oCH, NONACTIN R'OR’OR’ICH, an cm. MONACTIN R‘-R’-CH, R'-R‘-C.H. DINACTIN RNCH, R’ -R‘ -R‘ -C,H. TRINACTIN R'oR’uR3-R‘-C,H. TETRANACTW mm 0 0 <0 .> bk) 18-CROWN-6 (18C6) CZ f‘o’fi (01° °Z© 0 O K/K) DIBENZO-18-CROWN-6 (DB18C6) Figure l. (\sA. O O K/S\) 1,10-DlTHlA-1806 (DT18C6) 3 CH, (Cr-1.1.01 \ 01-1104 1, 0’CH- ~co ,CHCO\ NHC /c ,NH L-Lac ICH,1,cn\ ,co o-v.n\ CH J o \ +1 1 . V" \ $0 NH I (CHmCH—C‘H L’Vax )\\ \D-Val CH—CH1CH,1, Cg” L-Lu/ \O /D-Val /c / L- Val COO /CHICH,1, ‘ H D-Hylv o \ L-Val O-Hylv . C / NH'COCH-O'CG (CH,),CH CH, CHlCHfl. CHCCH,). VALINOMYCIN K/NQO 1,10 01A"sz 18C6 (omaco) mm o 0 [:1:0 0:I:) K/OQ DICYCLOHEXYL-lflCb (DC18C6) Structures of some naturally occuring and of some synthetic macrocyclic compounds. HISTORICAL REVIEW A. Neutral Macrocycles Macrocyclic ligands are uncharged species and contain a cavity in which a cation can be encapuslated. Some naturally occuring macrocycles, which are antibiotics, have been shown to be capable of actively transporting certain metal ions across some biological membranes. Moore and Pressman (16) reported in 1964 that antibiotic valinomycin (Figure l) is highly selective toward the K+ ion as compared to Na+. The observation has stimulated studies of metal ions complexed with various antibiotics and synthetic multidentate macrocycles such as crown ethers and cryptands (7,17-20). One goal of this work was to understand conditions which lead to differences in the transportation of alike alkali ions by the cell membrane in living systems (21,22). The antibiotic ionophores can be cyclic or acyclic whereas the synthetic ligands can be acyclic. monocyclic or polycyclic. Various antibiotics were used as models for the transport carriers (23) in the study of transport reactions of metal ions across synthetic or natural membranes (19.24.25): during transport the transport carrier separates the cation from its coun- terion and solvating liquid. Transport reactions can also be induced by synthetic carriers such as macrocyclic polyethers. A liquid hydrocarbon phase (containing carrier) interposed between two aqueous phase has frequently been utilized as a model for studying ion transport through natural membranes (26-28). The most well-know antibiotic ionophores are valinomycin and nactin (Figure 1); their selectivity toward metal ions depends on the coordinative characteristics of the cation as well as the reaction medium. The general selective sequence of alkali ions with these two antibiotics in aqueous solution is K+ > Rb+ > Cs+ > Naf > Li+ (29-31) which is the same as that with the 30—skeletal atom crown ether, DB3OClO (32). The sequence for the larger three cations varies Oppositely with their hydration energy cri- terion (33) (Cs+ > Rb+ > K+ > Na+ > Li+) which indicates that the cavity size has a strong influence on the stability of macrocyclic complexes. B. Macrocyclic Polyethers and Their Complexes in the Solid State Complexes of transition-metal cations with conventional ligands have been known for a long time. whereas 15 years ago only a few stable alkali cation complexes had been identified. Coordination chemistry of alkali and alkaline earth cations has started develOping rapidly only in this decade. Macrocyclic polyethers, which are similar to the antibiotic ligands both in structure and in their ability to form stable complexes with alkali and alkaline earth cations, were first reported in 1967 by Pedersen (1.34). On the Pauling scale, the electronegativity values of all alkali and alkaline earth metals very from 0.7 to 1.2. Taking the electronegativity of oxygen as 3.5, the bonds between these metals and oxygen should be about 70-85% ionic in character. Furthermore, in view of the low ionization potential of such metals and their hard acidic character, a covalent bond between these ions and hard base like oxygen atoms is rather unlikely. Macrocyclic polyethers are neutral compounds containing four to twenty oxygen atoms each separated from the next by two or more carbon atoms. The most effective complexing agents are those containing five to ten oxygen atom each separated from the next by two methylene groups (-CH20H2-). These compounds form polyether-salt complexes in which the cation is encircled by the oxygen atoms of the polyether ring and held by ion-dipole attraction between the negatively charged oxygens of the C-0 dipoles and the cation. The sta— bility constants of macrocyclic polyethers are three to four orders of magnitude higher than those of Open chain analogs (35). This effect has been referred to as the macrocyclic effect. One of the most striking characteristics of the macrocyclic polyethers is their ability to form complexes selectively with various cations. The factors affecting the formation and stability of these ion-macrocycle complexes include (a) the relative size of the ion and macrocyclic cavity (b) the electrical charge of the cation (0) the nature of the donor atom in the ring (d) the number of binding sites in the ring (e) steric hindrance in the ring (f) the solvent and extent of solvation of the ion and the binding sites (g) the nature of the counterion. The relationship between the cationic diameter and the cavity size is the most important factor which has been used widely to explain the stability and the stoichiometry of metal-crown ether complexes (4,7,17-20). Ever since the appearance of the first comprehensive report by Pedersen (1,34), it has been believed that complexation of a cation with a crown ether is determined basically by the fit of the cation in the cavity of the ligand. The ionic diameters of some cations and the estimated cavity size of the holes of selected cyclic polyethers are given in Table 1. For those having the best fit, 1:1 com- plexes are postulated to be formed in solution as well as in the solid state. In such a complex the ring oxygens of the crown ether are arranged equatorially around the cation, which remains exposed on the axial sides to the counteranion and/or solvent molecules as shown in the complex of KSCN-1806 (Figure 2) (35). The fact that a metal ion forms a 1:1 complex with a cyclic polyethers does not always indicate that the metal ion is located in the cavity of the polyether. As the cavity size of the crown ether increases for a given size of cation, 1:1 complexes are still obtained, but the ligand tends to be folded around the cation (this is designat- ed as wraparound encapsulate). Such folding of the ligand has been observed for dibenzo-30-crown-lO around potassium in Influbu ~.s~ “1111111: 9/1 1 . , ... uh... Drum: n... U. CZOOLCQE CG CG mwyu .. , .nOi.+~fi1.Hv CCOmPfiru no.» ~.~ dd. P H .1 90 k in LOIOEQfiQ o 1” Mud .H.n~ uprm .Uoms mamoos Aammv uoammanpouamwcompfim npwcmwm opp cam mamcoe AmADVCoPHoM1mCHH5mmnzmnoo msp op msv ma monopowwwv th>Mo w mm.m +mmq o: N +Npm mm N +th co m +Nmo 2: a +mw2 a: ...st os.m .mmm ow.m +HB mm.m +w< dm.m +mo mm.m +nm m.:1:.m mnczogouam HH< oo.m +x m.m-m.m oussou01ma Ada om.H +mz N.N15.H mocsononma HH< om.a +Hq m.H1N.H :1czoponma HH< Amy ampmemwc sowpmo Cowpmo waxy pmposwwu hpfi>mo ucmwwq .Ao:.:m.av onapwo com mpwcpm owaomoopoms vmpomamm %o N cw nopmemfla .H wands 10 Q ’. I> s" ' II I I ‘ .1. ‘. Figure 2. Crystalline structure of (KSCN-18C6). Figure 3. Three-dimensional crown complex of (KI-DB3OClO). o~¢ .... 11 the complex K(DB3OClO)I (36) (Figure 3) and for dibenzo-24— crown-8 around sodium in the complex Na(DBZ408)X (37). Alternatively, bimetallic complexes are produced in which two cations are complexed in the unfolded cavity of the ligand as found in the complexes (KNCS)2(DB2408) (38) (Figure 4), (Na-O-nitrOphenolate)2(DB2408) (39) and as expected for the complex of Na with DB3OClO (41). Also, three kinds of sodium- DB3OClO [Na°DB3OClO, NaZ'DB3OClO and Na3°(DB30010)2] complexes are found in the complexation of DB3OClO with a sodium salt in nitromethane and acetonitrile by a 23Na and 13C NMR study (42). When the size of the cation exceeds the cavity size of the crown ether, the metal ion is too large to fit exactly in the hole. In such cases ML sandwich complexes are formed (L: 2 crown ether). Sandwich complexes are formed by B1505 with potassium, rubidium and cesium ions in solution (43,44) as well as in the solid state (Figure 5) (23,41). The formation of sandwich complexes of Cs+ with 18-crown-6 and K+ with 15- crown-5 in different solvents were also reported by Mei (11) and Shih (45). In the sandwich and wraparound complexes, the crown ethers isolate the cation from the counterion and the solvent mole- cules. These encapsulates are comparable to those obtained from cyclic antibiotics (46,47) and information derived from the formation of the former is used to understand the latter. When the relation between cation size and polyether cavity size is the only consideration, cation-crown ether interaction -~v :1. 12 Figure 4. Crown complex of (2KSCN-DB2408). 0510“” I, cum f‘.' ,0“) 1. _, 09 0 C(12) ‘ ‘ 1I cum ' ‘Mn‘. '. cw) cum . (p on) 09’ on) ‘, mm cm) '. cw) .Hflfl mu" mm C(S)‘ Figure 5. Sandwich structure of (K+-2Bl505). 13 is most favored for a cation of the size nearest to that of the cavity. For example, 1204 is most selective for Li+, 31505 is for Na+, D01806 is for K+, and DB2408 is for Cs+ (43,48-50). The next preference of a crown is for a cation which is larger than its cavity. For example, B1505 forms a more stable complex with Rb+ and Cs+ than with K+ (9). The least favored ion of a crown ether is for a cation of a size smaller than the cavity (51). The general cation selec- tivity of several neutral ionOphores was compiled and is shown in Table 2 (52). Izatt 23.él- (52) has discussed in detail the other factors affecting the formation and stability of ion-macrocycle complexes. 0. Complexation of 18-Crown-6 and Its Substituted Analogs in Solution Over the years, l8-crown-6 and its substituted analogs have probably been more studied than any other crown ethers since the cyclic ethers' coorelation of selectivity with cavity size is restricted essentially to 18-crown-6. The first synthesis of 18-crown-6 was reported by Pedersen (l). The method used was potassium t-butoxide catalyzed cyclization of hexaethylene glycol monochloride in 1,2-dimethoxyethane. Unfortunately, the yield by this method was only 1.8%. Improved methods were developed by succeeding workers (53-56)- The stability constants of 1806 complexes with alkali and 14 Table 2. Cation Selectivities of Several Neutral Iono- phores (56) in Solution. Ionophore Selectivity Sequence Valinomycin Enniatin A Enniatin B Beauvericin Nonactin Monactin Dinactin Trinaotin Antanamide 'Cryptate 211 Cryptate 221 Cryptate 222 15-Crown-5 18-Crown-6 18-Crown-6 Benzo-l5-crown-5 Dibenzo-24-crown-8 Dibenzo-27-crown-9 Rb > K > Cs > Ag > T1 >> NHu > Na > Li Ba > Ca >Sr >'Mg K > sz Na > Cs >> Li Rb > K > Cs > Na >> Li Ca > Ba > Sr > Mg Rh > Cs > K >> Na > Li NH“ NH“ NH“ NH4 Na Li Ca Ag Sr As Ba T1 T1 Pb Pb VVVVVVVVVVV > Ksz > Cs > Na > K > Rb > Cs > Na > Ba > Ksz > Cs > Na > Ba > Rb > Na > OS Li > T1 > K > Rb > Cs Na > KxRb~Cs SrwBa Tl > Na > K > Lisz > Cs Ca >'Ba > Mg Tl > K > Rb > Na > CszLi Sr>Ca>Mg Ag > Csz’zNasz K > waAg > Cs > Na > Li > Ca > Mg Ba>Sr>K>Rb>0szNa Nasz > K RbNCSzK > Na K > Na~0s 15 alkaline earth cations are compiled and shown in Table 3. Complexation of 1806 with alkali and alkaline earth cations in water and 70% methanol/water solution was studied by Izatt gt al. (12). Using a calorimetric technique, they found the maximum stability for complexes of 1806 occurs at a metal ion to cavity diameter ratio of unity. The increased stability of the complexes is due to the enthalpy term. Some trends of stability constants for complexes of 1806 with alkali metal ions were also found by Frensdorff (43) using potentiometric techniques. Recent multinuclear NMR studies on complexes of Na+, Cs+, and Tl+ ion with 1806 in several organic solvents shows that the stability of 1806 complex is strongly influenced by solvent (57). Two of the most widely used crown ethers have been dibenzo—lB-crown-6 (DB1806) and dicyclohexano-lB-crown-6 (D01806). A major reason for this is that Pedersen reported complete details of the preparation of both compounds (58). The stability constants of DB1806 and four isomers of D01806 with alkali and alkaline earth cations are compiled in Table 4 and 5 respectively. Complexation of DB1806, cis- syn-cis-D01806, and cis-anti-cis—D01806 with alkali and alka- line earth cations were studied by Shchori gt g1. (59) using spectrophotometric technique. The representative structure of the complex of DB1806 with RbSCN is shown in Figure 6. For all ligands, the strongest complexes are formed with K+ 2+ and Ba which are of exactly the correct size to fit into 16 Table 3. Stability Constants of Mn+-1806 Complexes. Cation Medium Log Kf Methoda Reference Na H20 0.80 CAL 10 K 2.03 Rb 1. 56 Cs 0-99 Ag 1.50 T1 2. 27 Ca 0.5 Sr 2. 72 Ba 3-87 Na 70/30 Wt% MeOH/HZO 2.76 CAL 16 K 4.33 Rb 3.46 Cs 2.84 Ga 2.51 Sr 5.0 Ba 6.0 Na H20 0.3 POT 43 K 2.05 Cs 0.80 NH,+ H20 1.1 POT Ag 1.6 17 Table 3. Continued. Cation Medium Log Kf Methoda Reference Na MeGH 4.32 POT 43 K ' 6.1o Cs 4.62 l.30(log K2) T1 crystal 1:1 SPEC . 125 complex Na PC > 4 23Na,13308 57 205T1 NMR Cs 4.14 Na AN 3.80 Cs > 5 T1 > 5 Na DMF 2.23 Cs 3-93 Tl 3-35 Na DMSO 1.41 Cs 3.04 Tl 1.92 Na H20 0.8 Cs 0-99 T1 2.27 aPOT, potentiometry: CAL, calorimetry; SPEC, spectrOphotometry. 18 Table 4. Stability Constants of Mn+-DB1806 Complexes. Cation Medium Log Kf Methoda Reference Li H20 3 O SPEC 59 Na 1.16 K 1.67 Rb 1.08 Cs 0.83 As 1. L11 T1 1.50 NH4' 0.30 Ca 3 0 Sr 1.0 Ba 1-95 Li DMSO x O CON 51 Na 3.31 K 3-39 Rb 3.36 Cs 3-07 Li DMF 2.99 Na 3-35 K 3.56 Rb 3.52 19 Table 4. Continued. Cation Medium Log Kf Methoda Reference Cs DMF 3.48 CON 51 Li PC 3.22 Na 3.86 K 5.10 Rb 3°74 Cs 3°54 Na AN 5.00 POL K 4.70 Rb 3-70 Cs 3-50 T1 4.90 K MeOH 4.60 T1 4.00 Cs AN 1.54 l330s NMR 11 AC > 3 PC 3 3 FY 3.84 2o36(10g K2) DMF 1.48 DMSO 1.34 aCON, conductometry; POL, polarography; SPEC, spectrOphotometry. 1 -1:5... its. .... ....._:.s...:o.o >.s.:~..:...s.n .... bison. 20 2:.m as om.m w< mm.o mo mm.a om NO.N M OH HN.H sso omm oz Hm.: mo Ho.© x mo.: 2062 NZ as 0.0 Boa omm as sm.m mm :N.m mm o R do mm.a mo mm.H pm mH.N x mw.Humd.H mz on e.o omam mm.omm as oomH6o1mao-sam-mao monopommm mm mod mvozpms Esfivos Coflpwo csmwwq .moxososoo possum-+ss so mssmsmsoo spaasomsm .m manna 21 Hw.oo OH sm.m ms.m om.m mm.m oo.m ms.m :H.: mo.~ ob.o om.o ms.s oo.m sm.m sp.m mw.a mm.H sm.m sm.m wowHOQ 1msmspnflpsw1msmnw oomaom stmgpnszmumsmup eomHon-mno-sam-mso monohohom ex mos moossos enemas .oossassoo .m oases 22 0m.0 s aa 00.m 000 0002 mz mm.m mm m0.m am 0 a 00 00.0 00 00.0 om 0s.a m s 000a00 00 00.a-0a.a 0mam 0 m 02 -maouapsm-mao 00.0 m¢2m00 mma 0.2 00.0 no 0s.m a<0 000 mm 0m.0 0002 as 0s.s as 0a.0 m0 00.0 pm 00 00.0 aoa z< x Aosssxasv000aom wocmhmgmm MM Mon «cospos 850002 Cowpmo undwwq .0oosaps00 .0 oases 23 .zsposoapcopom .90m .> nzppmsoponmospoogm .ommm .m awhwohmaom .qom ppmeflhoawo .A cis-anti-cis-D01806 > trans-syn-trans-D01806 > trans-anti-trans-D01806. Several mixed donor macrocyclic polyethers have been reported (62) in which some or all of the ether oxygens were replaced by other atoms, such as S and NH. This replacement 26 affects not only the size of the cavity but also the type of coordination and the selectivity. By using potentiometric techniques, Frensdorff (43) first noted that when amine or sulfur is substituted for oxygen in a crown ether, the macro- cyclic effect Of 1,10-diaza-18-crown-6 (DA1806) and aza-18- crown-6 disappears. Anderegg (63) studied the complexation 2+ 2+ of Ag+, Cd and Hg with cryptand 222, DA1806 and H2N(-0H2— CH2-0)2-CH2-CH2NH2 in water. Nearly the same value of the stability constant for cryptand 222, DA1806 and their linear analogs verify that for the above cation the macrocyclic effect does not exist for the above macrocycles. The repre- sentative results are shown in Table 6. Metal complexes of macrocyclic ligands containing both nitrogen and oxygen donor groups have been found (43,64-66) to form 111 complexes with metal ions located in the center of the ligand cavity. The complexing of alkali or alkaline earth ions is diminished appreciably as nitrogen is substi— tuted in the ring, and the stability constant falls in the order of decreasing electronegativity of the substituted group, O > NR >NH. The effects on the complexes of post- transition-metal ions of similar sizes, e.g., Ag+, were exac- tly the Opposite and the stability of the complexes increased with substitution. It was concluded that only electrostatic bonding exists in the potassium complexes whereas the Ag+ complexes have both electrostatic and covalent bonding (43) The structure Of KSCN'DA18C6 (67) complex consists of .PCmsouswmms pow 00000 cop 00 H0 004 N U as n a + a0 soapomos homo Q: H q + 2 Cowpomon 0009 27 .0-ssoso-0a-0a0pa0-0.a .0 .000-0-000-000-0-000-000-0-0 000-0- 00-000-0-000 .0 .002-000-000-0- 00-000-0-000-000.200 .00 00.a- 00.0- a0.0 0a.0a- 0 +000 00.0 00.a- 00.0 00.0a- 0 +00 0 00.0- 00.0- 00.0 00.0a- 0 +000 00 00.0 00.0- 00.0 0a.:a- 0 +00 0 00.0 0.0 0.0 +000 00.0 00.0a- 0.0a +000 0.0 0.0a- 0.0 +00 0000 00.0 0.0 - 00.0 +000 00.0 0a.0a- 00.0a +000 00.a 0a.0 - 0.0 +00 000a00 00.0 +000 0.0 0.00- 00.0a +000 00 00.0- 00.0a- 0.0 +00 0 AHw£\HmOxV Aaofi\amomv N AHO$\HmOxV Aao%\HmOMv H Cow .000 omqe 000 o0 000 omqe o0< n0 0oa -smo 00sm0aq .0o00 pm soasaaom 0:00:00 :0 mpozpomaom UopSPHpmnsmnwflseJHO100 Sr2+. Recent multinuclear orderinngg > Ag+ > Cd2+ > Ba NMR studies on the complexation of Li+, Na+, and Cs+ ion with DA1806 in several nonaqueous solvents show that the general selectivity sequence for M+ with DA1806 is Li+ > Na+ > Cs+ (70). i F.‘ —., an 11 r. 29 00.0 00 00.a mz ma.N 00 fig 00.a 00 00.m om 0a 0N.N 00 mm.: 20 Ha 00.N 00 00.0 002 0a on m A momma.0ZMN.flqm 22 HA 00.0a 00 00.0 00 00.N 0m 00.0 000 00 00 0.0 a00 000 00 00 00.0 000 0000 0 000a00 00:000000 0 004 000:902 850002 sowpwo cummfiq .x0a0so0 000a00- so 000a00-+ss 00 mpzmpmsoo apaaasmpm .0 0a000 30 00.N He a0.o mo N0.N 00 02 0 as 00.0 mzszNHe mo 00 00.0 .mmamo.000z :2 02 0a.0 00 00 00.0 a00 000 as 00.0 000 00 0 0a.a 000 0000 0 000aea N0.N 00 NH.: 02 00.0 00 aa 00.0 022 omso 02 on 00.0 momma.mZmN.0A0 020 mu ooma0o 002090000 0 004 muonpmz 830002 £00900 020009 .0000apso0 .0 0a000 31 .th0EO0PC0Pom .eom .00008000000 .0000 3.0 000 E 30.0 as om.o mo mm.0 man 02 m A 09 00.0 00 mw.0 z< 02 00.0 mzz momde mo 0 a a mm mm 0 MMHmo mm0z om 02 wwwHBQ 00200000m M moq 000:002 830002 £00000 vc0m0q .00SC0pzou .m 00n0e “a c: is ‘I'. v "v t. 9.5:“ ‘ w' (we tr“ U“ Tm 32 Donor atoms such as sulfur has been used to replace oxygen in macrocyclic ethers to vary the metal ion binding properties in the ring. In 1960, Dann, Chiesa and Gates of the Kodak Research Laboratories synthesized l.lO-dithia-18- crown-6 (DT1806) by the reaction of sodium sulfide and l,2-bis(2-chloroethoxy)ethane (71). The first study sulfur- containing crowns seems to have been conducted by Pedersen (72-74). Crystal structure studies show that the sulfur substituted lZ-crown-h, lS-crown-S, and lB-crown-é direct their sulfur atoms away from the cavity (75). Izatt gt El- (76) compared the complexes of several thia-substituted poly- ethers to their linear analogs, and representative results are shown in Table 6. The formation constants of Ag+ and 2+ Hg complexes of the linear ligand are only sligtly larger than those of the cyclic ligand. The results show that, in contrast to the aza-crowns, no macrocyclic effect exists in the thia-substituted crowns. The crystal structure of PdCl complex of DT1806 (77) 2 shows that only outwardly turned sulfur atoms participate in coordination with the Pd2+ 2+ ion. As shown in Figure 8, the Pd ion lies outside the ring which is bent like a bow. This coordination is also observed in the crystal of HgClz- 1,4-dithia-18-crown-6 (78). The absence of a macrocyclic effect in these thia-substituted crowns is probably due to the fact that only sulfur atoms of crowns participate in the coordination with metal ion. In the series of studies of ~_0_ suz. .. 0 x f 33 ' Ago 6‘ “3‘ «'1 s» Mo’s RS?) .2. a9 ’ ~3' Figure 8. The structure of the (PdCl oDTlBC6) complex (the Pd coordinate to two ghloro ligand and two sulfur atoms of thia ether). "PW? *3 . CF09? C900“ trans-anti-trans trans-syn-trans cis-anti-cis .0 I) 5g “Kvavji‘ HLvth é cis-syn—cis trans-cis Figure 9. The isomers of D01806. . Ui‘ ‘ N M \v. '9 r .. X alv A... sNIH l l a «J -4. QM 34 thia-substituted crown with Ag+ and Hg2+ ions, Izatt g; 3;. (75) have found that the complex stability is enhanced by increasing the number of sulfur atoms in the ring. Alkali and alkaline earth metal ions give no evidence of complexation when all of the oxygen atoms in crown ethers are replaced by sulfur atoms (79,80). However, complexes of these ions are expected for the mixed crown ethers. Izatt 23,3l- (76) studied the complexation of several thia derivatives of 9-crown-3, lZ-crown-h, lS-crown—S, 18- crown-6, and zu-crown-B with Ag+, Hg2+, Tl+, and sz+ ions in aqueous solutions and in 70% methanol by calorimetric tech- nique. A partial substitution of sulfur for oxygen in lS-crown- 5 and l8-crown-6 ligands greatly increases the affinity of these ligands for Ag+ and Hg2+ ions but decreases the affi- nity for T1+ and sz+ ions. Stoichiometries of 2:1 (ligand/ metal ion) were found for many thia-substituted crowns with Ag+ and Hg2+ ions but only lsl complexes were found for Tl+ 2+ and Pb Frensdorff (43) showed that the substitution of two oxygen atoms by two sulfur atoms in lB-crown-6 drastically decreases the log Kf (formation constant) value from 6.10 to 1.15 for the potassium complex, but increases it from 1.60 to 4.30 for the silver complex. The results also show that the silver ion has a greater affinity for DT1806 than the potas- sium ion. In this case. Frensdorff postulated that in (DT18C6°Ag+) complex the silver ion can form ionic bonds with 35 oxygen atoms as well as covalent bonds with sulfur atoms. In a calorimetric study of monothia-18C6 complexes in methanol, Izatt et al. (81) showed that the substitution severely decreases the stability of the Na+ and K+ com- plexes but increases that of the Ag+ complex. Recent multi- nuclear NMR studies (57) on complexes of Li+, Na+, Cs+, Tl+ and Ag+ ion with DT1806, 18-crown-6, trithia-lZ—crown-h and lZ-crown-h in several nonaqueous solvents have showed that in all cases the substitution of the sulfur atoms for the oxygens results in a substantial decrease in the stability of complexes, while the stability of complexes varies inversely with the Gutmann's donor number of the studied solvent (57). D. Effect of Solvent on The Stability of Macrocyclic Complexes In the complexation process between crowns and metal ions in solution, macrocycles must compete with the solvent mole- cules and counterions for the cations in solution. In the case of no data available in literature about the ion pair formation constant of salt, the relative complexing abilities of the ligand without considering the ion pairs formation can be used to represent the lower limits of complex formation constant. The complexation process can be represented by following equation: (Mn+) 5x + (Crown) 8y 2 (Crown)n+ 82 + (x + y -z)S (1.1) r“ .l a a 4n 3 El '1‘ 36 in which Mn+ is metal ion, S is the solvent molecule, x,y and z are the solvation numbers of the metal ion, the ligand, and the complex respectively. In solution, the metal ion, the crown and the complex are solvated. Therefore, the for- mation of a complex is a result of competition among the metal ion, the macrocycle, and the solvent. As a result, changing the solvent can significantly affect the complexa- tion process. In 1971, Frensdorff (03) noted that the stability cons- tant of 1806 complexes with alkali cation were three to four decades high in methanol than in water. The same effect is observed in the complexation reactions of cis-syn-cis-DC18C6 and cis-anti-cis-DC18C6 (11,59). Popov and co-workers have studied extensively the complexation of alkali cations by macrocycles in various organic solvents using multinuclear NMR techniques (11.82-86). Their studies showed that the stability of macrocyclic complexes depends not only on re- lative cation size and macrocyclic cavity but also on the nature of the solvent in which complexation takes place. Observations on DB1806-cation complexes in DMSO, DMF and PC solutions (51) show a strong solvent effect on complexa- tion. The results are listed in Table 4. In all of the three solvents, the stability constants of alkali ion complexes are enhanced as the donating ability of the medium decreases. When the solvent is changed from the most strongly solvating solvent, DMSO, to the weakest one, PC, the stability 3. 4+ V.& C‘ .l t. 37 constants (log K) of Li+ and Cs+ complexes shift from 00 to 3.22 and 3.07 to 3.54 respectively. The results indicate the stabilities of the complexes of larger cations are less affected by solvent than those of smaller ones. The large difference in ionic radii between Li... and Cs+ ions derive that the more strongly solvated Li+ ion has a significantly smaller relative stability constant than the Cs+ ion in DMSO. In the weakest donor medium (PC), solvent competition toward cation-crown interaction is reduced mostly in the case of smaller cations, so that the interaction effects of the cation with the anionic species become pronounced. The largely ignored crown-solvent interaction is also an important factor which affects the complexation reaction. Such an interaction appears to be important when the donor ring is small or flexible to form a protonated crown (2). In inclusive and sandwich complexes, the solvent is effec- tively excluded from the first coordination shell, as shown in Li+C211, Na+C222, K+0222 (inclusive complex) (87,88), and K+ (B1505)2 (sandwich complex) (11), the measured physical property becomes insensitive to the solvent and counterion. However, for the (Cs+°C222) complex (89) the cation is only partially encapsulated, the solvent or counterion can still interact with the complexed cation, the measured physical property remains depend on the nature of the solvent. .nur '0‘ C. 1. 3 av. PV h. up; :2 38 E. Thallium-205 NMR Measurement The determination of thermodynamics and kinetics of the macrocyclic complexes in solution has been achieved by electrochemical (90,91) spectrosc0pic (92,93), and calori- metric techniques (94,95). In recent years, NMR spectros- c0py has become a powerful technique for studying ionic solvation and complexation reactions in solution (96,97). To a very large extent, this progress is due to the develop- ment of Fourier transform NMR spectrosc0py. Resonance fre- quencies and linewidths of alkali ion NMR spectra have been particularly useful in the studies of the alkali complexes. Nuclear properties of alkali and thallium nuclei are listed in Table 8. Three potassium nuclei, 39K, 40K and ”1K, possess a magnetic moment (98). Of these, 39K is the most sensitive as well as the most abundant in nature (93-08%). The sensitivity of this nucleus (5.08 x 10'“) is, however, too low to get good NMR spectra for dilute solutions of potassium salts. Thallium-205 has been proposed as a useful probe for studies of the role of the potassium ion in biolo- gical systems (18) because of its relatively large NMR sensitivity, which is 285 times higher than that of the 39K nucleus. Also, its ionic diameter (2.80 X) is similar to the potassium ion (2.66 X). The large chemical shift difference 205T1+ 20501+ (280 ppm) between in the actins (Figure 1) and in valinomycin indicates that Tl-205 NMR could be a very III .. (...: f-hf‘ Fl '1.— 0t: w.~ H.027? CC“ ..00...30H< L..O 0.0 .70 .HTQOLAM LCfifiOSZ 39 000.0 0\0 00.00 000.00 00000 000.0 0\0 00.00 000.00 00000 0-00 x 00.: 0\0 000 000.0 00000 000.0 0\0 0.00 000.00 0000 0-00 x 00.0 0\0 0.00 000.0 0000 0-00 x 00.0 0\0 00.0 000.0 000 muo0 N 0N.m 0 N:00 x m0.0 omd.m Mo: 0-00 x 00.0 0\0 00.00 000.0 000 0-00 x 00.0 0\0 000 000.00 0200 000.0 0\0 00.00 000.00 000 0.00 x 00.0 0 00.0 000.0 000 00000 ARV 00:20 00300 03000300 00 m0 0» 30am 0030033Q< [0002 00.30 00 0300032 0>0P000m zp0>000mn0m 0000032 0003002 003030000 msz .0030800m 83000009 030 000000 00 000000000m 0000032 .0 00909 40 sensitive probe for the studies of ionic transport across membranes. Thallium-205 NMR could well be used to elucidate details about the type and arrangement of ligand atoms, and the dynamics of the binding and transport processes in naturally occuring membrane channels and pores (99). Bystrov gt §l° (100) presented the fact that the K+ and Tl+ complexes with valinomycin have nearly identical solution structures. The chemical properties of the two ions are sufficiently alike that the Tl+ ion can replace the K+ ion in several enzymes. The solvent dependence of the chemical shift for 205T1 is over 2600 ppm (101) in contrast to a shift range of 08 ppm for 7Li (102.82). 030 ppm for 23Na (103,104), and 0120 ppm for 133Cs (105). The greater sensitivity of the thallium-205 chemical shift to the environment of the T1+ ion makes it a better probe than alkali metal ions in ion solvation studies. The chemical shift of thallium-205 has been measured in aqueous solutions of thallium(I) hydroxide, fluoride, acetate formate, nitrate. and perchlorate of varying concentrations (106). In these salts, the ion pair formation is greatest for the hydroxide ion and least for the perchlorate ion. Thallium-205 NMR has been used for studying preferential solvation (101,107) and the relative solvating ability of the solvent in binary solvent mixtures (108). The order of preferential solvation toward the dimethylthallium ion is HMPA > DMA > DMF > pyridine. 41 The studies of Tl+ ion solvation in aqueous amide, mixed amide, water/pyridine, water/DMSO, and pyridine/DMSO mixed solvents were carried out by Hinton gt g1, (109,110). The results indicate that the structural effects of the solution are important in determining preferential solution. Convington's nonstatistical distribution theory has been used to study preferential solvation of thallium(I) ion in nine binary solvent systems. Using this theory, the equilibrium constants and free energies of preferential solvation were obtained by Hinton §3_g1, (lll). Ion pair formation cons- tants of thallium (I) salt in several solvents have been obtained by Hinton gt a1. (112,113)° CHAPTER II EXPERIMENTAL 42 1. Salt and Ligands Purification Thallium salts were of reagent grade quality. Thallium(I) nitrate (Alfa) and perchlorate (K & K) were purified by recrystallization from deionized distilled water and then dried at 120°C for two days. Ultrapure lithium chloride and perchlorate (both Alfa) were dried at 190°C for two days. Anhydrous silver nitrate (Baker, AR) was dried over P205 in a vaccum at 650C for two days. Potassium hexafluorophosphate (Pfaltz and Bauer) was recrystallized from deionized distilled water and then dried under vaccum at 110°C for three days. Potassium tetraphenoborate was precipitated by reacting potassium nitrite and sodium tetra- phenoborate in water. The precipitate was washed with deionized distilled water, recrystallized from acetone and then dried under vaccum at 60°C for three days. The ligand. l8-crown-6 (1806) obtained from the Parish Chemical Company, was recrystallized by complexing with ace- tonitrile (llh) and then dried under vaccum at 25°C for 2 days. The purified 1806 melts at 36-37°C [lit. m.p. 36.5- 38.000 (126), 39-#0°C (1)]. Dibenzo-lB-crown-é (DBl8Cé, Parish) was recrystallized twice from benzene and dried under vaccum at room temperature for three days. The purified DB1806 melts at 165-1660C [lit. m.p. 164°C (1)]. Substituted crown, 1,7,10 16-tetraoxa-h,lB-diaza-cyclooctadecane (Diaza- 43 ‘FN flv 44 18-crown-6, DA1806. Merck) was recrystallized from heptane and dried under vaccum at 25°C for 3 days, while 1,10-dithia— lB-crown-6 (DT18C6), obtained from the Parish Chemical company. was dried in vaccum at 50°C for one day. The mixture dicyclohexyl-lB-crown-6 (DC18C6) diastereo- mers was separated into two principal components by Izatt and co-workers (115) who had previously identified the two major isomers as the cis-syn-cis (DClBCo-A, m.p. 61-620C) and cis-anti-cis (D018C6-B, m.p. 83-8u00) isomers. The structure of these five diastereomers is shown in Figure 9. It should be noted that DC18C6-B also exists in a second crystalline from with m.p. 69-7000 (#9). The two isomers were separated by following the procedure developed by Izatt gt al. (115) except that the hydrogen sulfide gas was obtained by the decomposition of a sodium sulfide in a con- centrated aqueous solution with 20-30% phosphoric acid. The acid was allowed to drip slowly from a separatory funnel into the sodium sulfide folution. and the evolving H S gas 2 dried over CaClZ. Using this method, 31% of isomer B (m.p. 69.0-69.600) and 26% of isomers A (m.p. 60.5-61.20C) were obtained. The two isomers also have been separated by column chromatography on Woelm alumina (activity grade 1) using n-hexane-diethyl ether solvent mixture as eluents (49). However. this separation method is costly and very time con- suming with low yields of each isomer (115). 45 2. Solvent Purification Propylene carbonate (PC, Aldrich), nitromethane (NM, Aldrich), dimethylformamide (DMF, Mallinckrodt), dimethy- lsulfoxide (DMSO, Fisher), and tetramethylguanidine (TMG, Eastman) were refluxed over calcium hydride (Aldrich) under reduced pressure for one to three days, then fractionally distilled. Hexamethylphosphoramide (HMPA, Aldrich) was refluxed over calcium oxide (Fisher) under reduced pressure for 2# hours and then fractionally distilled. Tetramethy— lenesulfone (sulfolane, SF, Aldrich) was refluxed with sodium hydroxide pellets under reduced pressure for 10 hours and then fractionally distilled repeatedly until 1 ml of sulfolane did not develop a visible color within 7 minutes after the addition of an equal volume of 100% sulfuric acid. Acetone (AC, Mallinckrodt). acetonitrile (AN, Mallinckrodt) and tetrahydrofuran (THF. Baker) were refluxed over calcium hydride and then fractionally distilled. Methanol (Mallinc- krodt) was refluxed over magnesium turnings and iodine for 12 to 2b hours and then fractionally distilled under nitrogen at atmospheric pressure. All of these solvents after fractional distillation were transferred in a dry box under a nitrogen atmosphere and further dried for 4-20 hours over freshly activated 38 or QR molecular sieves. These sieves were washed with distilled water, then dried at 110°C for several days, and finally (L 46 activated to 500°C under a nitrogen atmoshpere for 2h hours. Solvents such as methanol, DMSO and even acetone decompose and turn yellow after a prolonged standing over molecular sieves (116). The water content of purified solvents was determined using a Varian Aerograph Model 920 gas chromato- graph and was found to be always below 100 ppm. The purity of these solvents was also checked by 13C NMR. The deuterated solvents, chloroform-d (Aldrich Gold Label), acetonitrile-d3, acetone-d6, D 0 and methanol-d4, all 2 from Stohler IsotOpe Chemicals, were used as received. 3. Sample Preparation In view of the hydroscopic nature of the nonaqueous solvents and of the reagents, all of the solutions were prepared in a dry box under a nitrogen atmosphere. Samples for mole ratio studies by 205T1 NMR (or 13C NMR) were usually prepared by weighing out the various amount of the complexing ligand (or salt) into a 2 ml volumetric flask followed by dilution with the metal ion solution (or ligand solution) which was previously prepared by dissolving the salt (or the ligand) in a desired solvent or mixed solvents. After dissolution of the ligand (or salt), the solutions were transferred to 10 mm or 8 mm NMR tubes, capped, and wrapped with teflon tape to prevent both contamination by atmospheric water and solvent evaporation. In the case of the studies of competitive solvation of 47 Tl+ ion in mixed solvents, the solutions were prepared by mixing the desired solvent mixture with concentrated thallium(I) salt solution which was previously prepared by dissolving the thallium(I) salt in one of the two solvents. The resultant mole fraction of each solvent in binary solvent can be calculated from the known volume and specific gravity of the solvent. 4. Intrumental Measurements A. Thallium-205 and Lithium-7 NMR All 205T1 and 7Li measurements were carried out on a highly modified Varian DA-60 pulsed Fourier transform mode spectrometer equipped with a wideband probe capable of multi- nuclear Operation (117). The spectrometer was equipped with an external proton lock to maintain the stability of the magnetic field at 14 Kilogauss (1.4 Tesla). The nicolet FT- NMRD program (118) was Operated by a Nicolet 1080 computer system for the data acquisition and Fourier transform. Lithium-7 and thallium-205 were measired at 23.32 MHz and 34.61 MHz respectively. Non-spinning 10 mm 0D NMR tubes (Wilmad) were used in all studies. The temperature was controlled to t 1°C as monitored with a calibrated Doric digital thermocouple. In the studies of temperature dependence of the 205T1 chemical shifts, each sample tube was left in the probe for 15 minutes to reach the equilibrium temperature before 48 measurement. The difference of 205T1 chemical shifts in some studied systems was enormous, therefore, most 205T1 NMR data were measured with the highest spectral width (SW) range of DA- 60,25000 Hz, which correspounds to 722 ppm for the ZOSTI nuclei. The errors of 205T1 chemical shifts depend on the line width of the resonance line and the signal to noise (S/N) ratio. As the line becomes broader or the S/N ratio becomes smaller, the chemical shift measurement becomes less accurate. In some systems, the maximum chemical shift range of 205T1 is smaller than 1000 Hz (29 ppm), in such cases, small spectral width, such as 1000 Hz, can be used for in- creasing the resolution of the measurement. If, in a studied system, the205T1 chemical shift range is over 25000 Hz (maxi- mum spectral width on DA-60), the foldover effect (aliasing effect) has to be monitored for very carefully, otherwise a wrong 205T1 chemical shift measurement can be obtained. As shown in Figure 10, which shows the expected and its serial NMR signal of mirror images are symmetrical about the vertical lines which represent the carrier waves with radio- frequcies v0, v0 t sw, vo t 25w, ----- vO t nSW. These images only appear if the Fourier Transform calculation is performed for the frequencies outside the range SW. However, any real line lying outside the sweepwidth SW which derived by wrong selection of radio frequency gives an image at an incorrect chemical shift of the spectrum. This u. l Hui 3 a 49 if]? M" 3176 Vo+ZSW Vo+SW Vo Vo-SW Vo-ZSW Figure 10. The mirror images obtained from a real line S0 as a result of Fourier transformation. Figure 11. Free induction decay for a set of identical nuclei with Lamor frequency, Vs, excited by a pulse of frequency exactly equal to Vs. CL $.U a Us 50 phenomenon must be eliminated to avoid incorrect interpre- tations. 0n the DA-60, the radiofrequency is controlled by mixing an adjustable frequency synthesizer and a 56.4563 MHz RF transmiter. The resonance frequency, Vs, of sample can be obtained by adjusting the frequency synthesizer, until the free induction decay (FID) observed by the oscillOSCOpe, has the shape shown in Figure 11. The total, anticipated, real spectrum of the studied system can be included in the real region by applying a suitable excitation frequency V0 at the edge of the spectrum, and by selecting an appropriate SW which is greater than the expected chemical shift range. If the FID signal is very weak, we cannot use the above method to find the resorance frequency. In this case, the following method can be used. 0n the DA-60, in the same acquisition time, the NMR intensity appea- ring in the real region is stronger than the one occuring in the imaginary region, so, the radio frequency, Vo, can be selected untill the strongest NMR signal is obtained, then the resonance frequency can be calculated from V0 and the chemical shift of the resonance signal. Figure 12 shows that the relative intensity of 205T1 in an aqueous solution of 1.5 M thallium(I) acetate (A) and 0.3 M thallium(I) nitrate (B) in which the resonance frequency of 34.6164 MHz for (A) and 34.6119 MHz for (B) are calculated. The resonance fre- quency VS of the sample can be calculated by the expression 51 .Aum ooomm .3m .moCosuoHH mocmcowou ”mm .hostUogM houwmocp scam «wmv pomeohPoomm owu zmuo> o> 3m+o> (D (I) m (r‘ 52 vS (MHz) = 56.4563 - SY - sw + CU (2.1) where SY and CU are the synthesizer and the cursor fre- quencies in MHz. Figure 12 shows that the magnitude of the chemical shift increases with increasing SY or decreasing frequency Vfliin real region but the inverse effect is found in imaginary region. In 7Li NMR measurements a sepctral width of 1000 Hz with 8K memory was used, and the chemical shifts were accurate to within t 0.1 ppm. In 205T1 NMR measurements, generally a spectral width of 25000 Hz with 8k memory was used. In this case, the accuracy of the chemical shift is within 1 0.5 ppm. B. Chemical Shift Reference and Correction The chemial shift of thallium-205 was first referred to a 1.5 M aqueous solution of thallium(I) acetate, and then corrected to an infinitely dilute aqueous solution of the Tl+ ion. The correction value for 1.5 M aqueous solution of thallium(I) acetate solution is +124 ppm. All 7Li chemical shift measurements are referenced to an external standard solution of 4 M LiClOu in H20. Reference solutions for 205T1 and 7Li measurements were sealed in 5 mm NMR tubes which were coaxially sealed into 10 mm tubes. The space between the two tubes was evacuated and vaccum-sealed. In this way, the chemical shift of reference solution will not be affected by ambient temperature change (119). In this thesis the r-J P *3 C)“ ‘v‘ ’ r l... 53 downfield chemical shift (high resonance frequency shift) from the reference is indicated as positive. The sign con- vention for NMR spectrum will be discussed in APPENDIX 1. The same external reference method was used in our studies. The reported chemical shifts were corrected for the diffe- rences in bulk diamagnetic susceptibility between sample and reference according to the following equations (120). _ __§1_ - corr _ bobs + 3 (Ksample Kreference) (2'2) _ 4h 6corr — obs + 3 ( reference - Ksample) (2'3) Where Kreference and Ksample are the unltless volumetrlc susceptibility (121) of the reference and sample solvent res- pectively, acorr and bobs are the corrected and observed chemical shifts respectively. Equation (2.2) is applied to the DA-60 spectrometer in which the applied magnetic field is transverse across the long axis of the sample tube, while Equation (2.3) applies to the Bruker WM-250 spectrometer where the polarizing magnetic field is along the long axis of the cylindrical sample tube. Dilute solutions (0.01 M) were used in our study, so the contribution of the added salt to the volumetric susceptibility of the solution was neglected (121). The correction values for various solvents with respect to water on DA-60 and WM-250 are given in Table 9. Line widths at half-height (Av) of about 12-20 Hz was 54 observed without spinning. Two solvent properties, dielec— tric constant and Gutmann donor member (122,123) are also listed in Table 9. C. Proton and Carbon-l3 NMR All LH and 13C NMR measurements were obtained on a Bruker WM-250 spectrometer Operating at a resonance frequency Of 250.13 MHz and 62.89 MHz for 1H and 13C respectively. The spectrometer was locked by deuterium signal Operating at a fixed frequency of 38.397 Mhz to maintain the stability of the megnetic field at 58.75 KG. The proton RF frequency is derived from a 10 MHz master quartz oscillator, mixed with a synthesizer frequency to 83.38 MHz, pulsed and then tripled to 250.13 MHz and amplified tO 25 watts. The spectrometer was coupled to an Aspect 1000 minicomputer with 48K Of 2D lock- memory. The probe heads are equipped for internal ing, 1H decoupling and variable temperature. The sample solution of 130 was usually contained in an 8 mm o.d. NMR tube (Wilmad) which was coaxially centered by teflon spacers in a 10 mm o.d. NMR tube containing deute- rated solvent as the lock. The sample solution of 1H was contained in an 5 mm o.d. NMR tube which contains some deute- rated solvent as the 1ock. The reported 130 chemical shifts were corrected for the differences in bulk diamagnetic susceptibility between sample and reference according to equation (2.3). L»4<§t:E:wC LCL, CCTQCCLLCC tit. nucvaCLCL; 9C0>~Cm >.¢.< .mm @HLSS 55 shoe mpo s + "so .amma.mmav mosoeoeomo .seaaeoapooomsm deposmmsmaa ossao> rasmm Ovasmuocgmonm - - . m.mm 0.0m -Hssposmxor ooo.o+ ooo.o+ ome.ou o.mm m.me seems mms.o- mmm.o+ «Ho.ou H.mn s.ma masseuse wvwxoMHsm mms.o- Hem.o+ moo.o- m.mm s.os -Hssposam ouwsmshOh oao.o- mom.o+ oom.o- 0.0m 5.0m -Hsspoefisuz.z mmm.ou mm:.o+ mam.o- s.mm s.mm Honorees mo.a- mem.o+ oe:.o- o.sa m.om ocopoo< mpdfionhmO omm.o- oma.o+ smo.o- H.ma o.mo osoasoohe . u I m.:a o.m: ocmaowasm dashes: ms.o- omm.o+ 2mm.o- H.sH o.mm -opoos mcmnpoe mum.H- mmo.o+ mam.o- s.m m.mm nospflz A893 .Hhooo A89: «.280 omNISB CO owldm Co OH x Honssz HOcOQ pCMpcho Ocowpoouuoo OcOflpoounoo Nmo>m DSCmEPso OfiHpOHOHHQ pso>HOm .omm-23 possum one so esm ooasa smfiem> map CO zpfiaflnflpmoomzw capocmwemfla how COHPOOHHOU paw moaphwnohm pzo>aom mom .m wanwe 56 D. Data Handling The formation constant of complexes in various system and ion association constants of lithium salts were calcu- lated on a CDC-6500 computer by fitting the NMR data with appropriate equations using a non-linear least squares pro- gram KINFIT (124). CHAPTER III COMPLEXATION OF THALLIUM(I) SALTS BY lB-CROWN-6 AND ITS SUBSTITUTED ANALOGS IN VARIOUS SOLVENTS 57 1. Introduction The significant correlation Of selectivity with cavity size for crown ethers is restricted essentially to 18- crown-6 and its substituted analogs. The main purpose of this thesis is to study the complexation Of the Tl+ ion with 18-crown-6 and its substituted analogs in various solvents, especially in nonaqueous solvents. Such studies provide useful information for separation chemistry and a valuable model to investigate the transportation of metal ion across synthetic or natural biological membranes. It has been found that nuclear magnetic resonance of alkali nuclei, such as 7Li, 23Na and 133Cs is one of the most powerful techniques for studying the complexation of metal ions with macrocycles in aqueous as well as in non- aqueous solutions (57.97.126,l27)° Thallium-205 NMR has also become an important probe for investigating the complex- ation and solvation characteristics of the Tl+ ion (57,110- 112) which has been proposed as an NMR probe for studies of the role of potassium ions in biological systems (18). The chemical shift Of thallium-205 is very sensitive to the chem- ical environment change of thallium(I) ion (101), so that the NMR chemical shift and linewidth of the Tl+ ion may give valuable information about the ion-ligand, ion—solvent, and ion-ion interactions. 58 59 The complexation reaction of 18C6 with thallium(I) ion has been studied quite extensively in aqueous solution, but less attention has been paid to studies of the complexing abilities between thallium(I) ion and a series Of derivatives of 18C6. The work presented in this chapter investigates the complexation reaction of the Tl+ ion with a series of crowns, such as 1806, DCl8C6, DB18C6, DA1806 and DT1806, in aqueous and several nonaqueous solvents by using thallium-205 and carbon-13 NMR techniques. These studies not only provide the stability constants of different complexes but also give useful information about the effects of the solvent, and the different donor atoms Of the ligands. Typical solvents, such as nitromethane, acetonitrile, acetone, sulfolane, dimethyl- sulfoxide and hexamethylphosphoramide were chosen as the reaction media. 2. Selection of External Reference Solution for Thalliwm- 20 NMR. The external reference method was selected for thallium- 205 NMR studies. This method is advantageous in eliminating the possibility of intermolecular interactions or chemical reactions between the reference compound and the sample solu- tion. Two aqueous solutions, 1.5 M thallium(I) acetate and 0.3 M thallium(I) nitrate, were chosen as the external ref- erences. Occasionally, these two solutions have been used for detecting the foldover effect which is described in 60 detail in section II-4-A. The chemical shift of thallium-205 was first referred to an external reference, and then cor- rected to that of an infinitely dilute aqueous solution Of Tl+ ion. Downfield (paramagnetic) shifts are taken as positive. The thallium-205 chemical shifts of thallium(I) perchlo- rate and thallium(I) nitrate in water solution are given in Table 10 and the variation of thallium-205 chemical shift as a function of thallium(I) salt concentration are plotted in Figure 13. In both solutions, the 205T1 chemical shift varies linearly with the concentration of the thallium(I) salt and the two lines intersect at the point of zero salt concentration (infinitely-dilute solution). An increase in the concentration of thallium(I) salt in an aqueous solution results in the replacement of solvent molecules in the thallium ion inner solvation sphere by anions. The effect Of these replacements may either increase or decrease the electron density of the cation depending on the properties of the anion. Comparing this with the results Obtained by Shih (45), we can conclude that the replacement of solvent molecules by symmetric polyatomic anions such as PF6-, Cth-, BPhu-, and N03-, will reduce the electron den— sity Of the cation resulting a upfield shift for paramagnetic nuclei, while for halide anions the replacement will increase the electron density of the cation inducing a downfield shift of the resonance. The possible reason may be that, in a 61 Table 10. Thallium-205 Chemical Shifts of Thallium(I) Salts in Water at 25 C. Salt Concentration 5(ppm) (M) TlNO3 0.4000 - 2.0 0.3000 0 0.2000 1.7 0.1000 3.5 0.0500 4.6 0.0010 5.9 0.0005 5.1 T1C10“ 0.5000 -22.8 0.4000 -17.8 0.3000 -12.9 0.2000 - 6.9 0.1000 - 1.4 0.0500 1.7 0.0250 3-3 0.0050 5.3 0.0025 5.0 0.0010 5.2 0.0008 5.1 0.0005 5-3 62 I I I -24 - -20 _ —l6 ” T1C10” -12 r- -8 __ A . E CL _ L. D. 4 V ‘0 o O _ TlNO 3 1+ .. 8 - l 1 1 0 0.2 0.4 0.6 CONCENTRATION IN H20(l) (M) Figure 13. Thallium-205 chemical shiftsogs. thallium(I) salt concentration in water at 25 C (0.3 M T1N03 in H20 as reference). 63 symmetric polyatomic anion, the negative charge can be dis- tributed on its large surface homogeneously, so it becomes a poor electron donating group relative to halide anions. The measurement indicates that the 205T1 chemical shift for 0.3 M of thallium(I) nitrate and 1.5 M of thallium(I) acetate are,a 5.5 ppm upfield shift and a 124 ppm downfield shift referenced to infinite-dilution aqueous Tl+ ion solu- tion as zero. According to these measurements, one can cal- culated the chemical shifts by the following relationships, 5 = 6 - 0 1 - 5.5 (3.1) or 6 = 5 - 5 + 124 (3.2) where 68 is the corrected sample chemical shift, érl and 6r2 are the Observed chemical shifts of 0.3 M T1N0 and 1.5 M 3 TlOOCCH3 external standard solutions respectively, 60 is the Observed sample chemical shift. 3. Results and Discussion A. Complexation of the Tl+ Ion by DB18C6 The compound T1C10,+ is readily soluble in many organic solvents and should be only slightly associated when the di- electric constant Of solvent is high. Therefore, this salt was chosen for our complexation studies. The dependence of the Tl-205 chemical shift on the mole fraction of DB18C6/T1010“ 64 in various solvents is given in Table 11 and these data are plotted as shown in Figure 14. It is Obvious that the sol- vent plays an important role in the complexation process. Figure 14 shows that the thallium-205 resonance shifts downfield with increasing the DB18C6/Tl+ molar ratio in the solvents with low Gutmann donor numbers such as nitro- methane, sulfolane and acetonitrile, but it moves upfield in high solvating solvents, such as dimethylformamide, di- methylsulfoxide and hexamethylphosphoramide. The data show that, in most studied solvents, the ligand ring size is ade- quate to accomodate the T1+ ion resulting in the formation Of 1:1 complexes. In Figure 14, two straight lines with intersection at 1 (ligand/metal ion) in the mole ratio plot in nitromethane solution, compared with the plots in other solvents, is an indication Of the formation Of a stronger complex between DB1806 and T1... ion in nitromethane than in all other studied solvents. However, in dimethylsulfoxide and hexamethylphosphoramide solutions, the 205T1 chemical shift varies linearly with increasing DB18C6/Tl+ mole ratio which indicates that the further addition of crown must pro- vide a change in the environment of the Tl+ ion or be used to form weak complexes and hence produces a chemical shift which varies linearly with ligand (crown) concentration. It is obvious that, in the (Tl-0131806)+ complex, the Tl+ cation sits in the crown cavity and is only partially encap- sulated, and may form an ion-pair with the anion. In the 65 mm s.mmmu :H.m ea m.mmma nm.: ma sm.mman sm.m mm m.mmm- os.m mm H.3mm- oo.m ma mm.mmau sm.: mm o.Hmm- oo.m mm m.:~m- sm.H ma ne.mmfiu os.m mm m.~mm- ma.H mm m.:mm- mm.a ma mm.HmH- so.m em s.omm- Hm.H as 0.5mm- so.H ma mm.oma- HN.H an H.0NN- co.“ as «.mnmu ~m.o ma oo.omH- mm.H am m.~o~- ms.o we s.msm- mm.o we mm.mma- oo.H mm m.mm~- om.o sew m.amm- mm.o we mm.ssau m:.o mm n.mmm- mm.o mm 0.56m- oo.o ma oo.mam- 00.0 on s.msm- o Asmvsq “shove +He\q Asmvsq Aeeeve +He\q Asmvs<_ Aseovo .He\q mm z< 22 .mpCm>Hom msoanw> as E 3.8583303?“ so mpmfism 182.98 momug on» go 35363 .3. sands 66 .2 moo.o ma soaoae co soaPmoPsoosoom cam m.Hsm mm.m cam o.Hmm mm.s cam m.mmm no.s cam m.mom om.m mmfi o.dsm nm.m com m.HHm ms.m mmfi s.msm sfi.m as o.msn ma.m ooofi n.3Hm mo.H me H.mmm mm.H mm m.msu mm.fi mmm m.mHm om.H mofi 6.3mm sa.a ms a.mfi- mm.H oom m.oam mo.H moa H.mmm ms.o ms m.m mm.o mafia 2.5Hm mm.o omfi m.mmm mm.o we p.02 Ho.o cam a.omm ms.o ONH m.smm mm.o om m.mu wn.o 6mm m.mam oo.o omH o.smm 0 mm m.mmH 00.0 :55 Ede; +3} :53 “see; .3} 355 2er .3} madam momso ego .emssepsoo .HH deems 67 -400 “300 “200 “KM? E 0 ' Q. 3 «0 I00 — 4 DMF 2°0— o DMSO .. O HMPA 30K)- ‘ - ——Hcm msOHnm> 0H AHH.000H00-ch mpHHsm HmoHsmco msHHHsHH ocm mesmHmsoo HPHHHompm .NH magma 72 Table 13. The Variation of 2055131 Chemical Shifts with DB18C6/T1C104(0.004 m) in Acetone (sw=1000 Hz). L/Tl+ 0(ppm) Av (Hz) 0 -240.4 15 0.21 -239-5 15 0.42 -238.9 18 0.50 -238.5 16 0.56 -238.1 16 0.69 -237.9 18 0.80 -237.9 16 0-97 -237.7 18 1.08 -237.8 18 1.18 -237.9 18 1.35 -238.2 16 1.50 -238.7 16 1.70 -239.5 16 1.87 -239.8 18 2.05 -240.5 18 2.29 -241.4 20 .-__. -———-—-—-—————- -.- .... . - 73 I I I —2Ll.ll. _ c- ~242 4 - A E g -... .. a; O 0 —238 s - _. I J l 236 1.0 2.0 3.0 4.0 [081806] / [TU] Figure 15. Chemical shifts of T1-205 vs. DB18C6/T1+ (0.004 M) mole ratio in acetone. 74 both 1:1 and 2:1 complexes with the thallium(I) ion. In this system, the observed chemical shift can be expressed as bobs = 5MXM + 6MLXML + 6ML2XML2 (3.11) where M, ML and ML2 are the solvated cations, 1:1 complexed metal ions and 2:1 complexed metal ions respectively. The complex formation constants K1 and K can be calculated by 2 the methods described in APPENDIX 2-B. The calculated for- mation constants and limiting chemical shifts are also shown in Table 12. The data collected in Table 12 show that the stability constants of the (DB18C6-Tl)+ complex in various solvents vary in the order nitromethane, acetonitrile > sulfolane > dimethylformamide > water > dimethylsulfoxide, hexamethyl- phosphoramide. In general, as shown in Table 12, the sta- bility Of the complex increases with decreasing solvent Gutmann donor number. These results indicate that, in com- plexation reactions, the donor ability Of a solvent plays a more important role than the dielectric constant. It is Obvious that in strongly solvating solvents the competition between the solvent molecules and the ligands for the coor- dination sites of the cation should decrease the formation constant of the complex. The formation constant of the (DB18C6'T1)+ complex in acetonitrile seems too large to be determined accurately by NMR techniques which is coincident 75 with the previously reported value, log K=4.90 (48). Table 12 shows that the limiting chemical shifts of the (DB18C6-Tl)+ complex in sulfolane, nitromethane, acetonitrile and dimethylformamide vary by as much as 100 ppm. These re- sults indicate that in this complex the Tl+ ion is only par- tially encapsulated by the ligand, and the solvent molecules and/or counter ions can still interact with the vacant coor- dination sites of the complexed T1+ ion. B. Complexation of the Tl+ ion by cis-syn-cis-DC18C6 The measured thallium-205 chemical shifts at different ligand/T1+ mole ratios for complexation of the Tl+ ion by cis-syn-cis-D01806 in various solvents are given in Table 14 and plotted in Figure 16. The results show that only 1:1 complexes are formed in these systems. In nitromethane and sulfolane solutions, the 205T1 resonance cannot be Observed when the ligand/T1+ mole ratio is between 0 and 1, due to a dramatic increase in the linewidth. A probable reason for this line broadning is the slow exchange of Tl+ ions between solvated and complexed sites. When the ligand/T1+ mole ratio is greater than 1, all Tl+ ions are complexed by the crown ligand, and the 205T1 linewidth become small again. The relative formation constants of the 1:1 complex have been obtained by analyzing the 205T1 chemical shift versus mole ratio data as described in section III-3-A. The calcu- lated formation constants and limiting chemical shifts for 76 0m 0.0mH- No.0 0m 0.mmH- H0.s mm 0.m0 No.0 mm m.amH- 00.0 mm 0.00 ms.m 0mH H.00H- mm.n mm 0.smH- Ha.m mm 0.00 om.m 00H 0.00H- 05.0 mm 0.mmH- NH.N mm 0.m0 m0.m 00H 0.00H- m0.m a: 0.00H- 00.H mm 0.00 mm.H 00H H.50H- 00.H as n.0mH- 0N.H mm 0.00 0N.H mmH s.s0H- 0m.H 0m H.NOHn no.0 mm 0.00 H0.H mmH 0.00H- H0.H 00 0.0mH- s0.0 00H 0.0HH- 00.0 0mm H.0HH- No.0 HHN 0.05H- 00.0 mmm s.m0H- 00.0 . - 00.0 0mm n.00H- m:.0 00H 0.m0H- 00.0 . - 00.0 0H 0.00m- 00.0 NH. 0.00m- 00.0 an. m.msm- 00.0 Heroes Aseovo HH\H Asmvaq “20000 He\q Asmvaq Henavo +HB\H 0d z< zz H2 H0. 01 00H0H5\000H00 mHo can mnoandmHHHsmHmcHEcco.mwMMMHmw Mwmmmmwemm .sH oHomH 77 .omcHMPQO on nonsmO Esnpoomw mocchme 0H0 0.00H 0H.0 sHH 0.00- 0H.0 00H 0.sNH- 00.0 000 0.00H 00.: 0HH 0.50: 00.0 00H 0.0NH- m0.0 0am 0.00H 00.0 00H «.00. 00.0 000 0.0NH- 00.0 0H0 H.00H 00.0 HOH 5.00- 00.H 000 0.0NH- 00.H H00 0.HHN m0.m HnH 0.0H- 00.H 000 0.0mHa 00.H H00 H.000 H0.H 05H 0.0 - 00.H 000 0.00H- 0H.H 000 0.000 00.H 000 0.0 a0.H 000 0.00H- 00.H 000 0.000 00.H H00 0.0H a0.0 0K0 0.00H- 00.0 :00 0.000 H0.H 000 0.00 00.0 - n 00.0 0H0 H.0H0 00.0 000 0.05 00.0 mmmH 0.00H- 00.0 000 0.000 H0.0 00H 0.00H 0H.0 000 0.000. 00.0 00H 0.000 00.0 mm 0.00H 00.0 NH 0.000. 00.0 Asmvaq A20000 +H0\H Asmvaq Aeoova +HH\H Asmvaq Hemova +He\q 0020 020 mm .000CHH200 .0H chme “400 ~300 -200 -H3C> 8. (ppm) ICHD ZCHD BCHD Figure 16. Chemical shifts Of T1- 205 vs__._ cis- -D018C6/Tl mole ratio_ in various solvents. . AC - SF - NM a AN ‘DMF o DMSO 2K) l 41) [DCIBCG] / [TU] 64) the cis- syn- 79 the (cis-syn-cis-DC1806:T1)+ complex in various solvents are presented in Table 12. The results show that the variation of the solvents can significantly affect the binding prOper- ties Of the ligand. In solvents with weak solvating ability such as nitromethane, acetonitrile and acetone, the 205T1 chemical shift is strongly affected by addition of the li— gands, and the mole ratio plot consists of two straight lines intersecting at the 1:1 mole ratio. This behavior indicates that the Tl+ ion is strongly complexed by the cis-syn-cis- DCl8C6. In such cases, the formation constants cannot be deter- mined by NMR techniques and we can only conclude that the log Kf > 5. It should be noted that, in an acetonitrile solution, polarographic measurements by Hofmanova gt 3;. (48) gave a log Kf value of 7.40. The stability constants of the (cis-syn-cis-DC18C6-Tl)+ complex in various solvents decrease with increasing Gutmann donor number of the solvents (Table 12) in the order nitro- methane, acetonitrile, acetone > sulfolane > demethyl- formamide > dimethylsulfoxide > hexamethylphosphoramide. C. Complexation Of’the T11 Lgn.bv 18C6 The complexation between the thallium(I) ion and 18C6 in organic solvents such as nitromethane, acetonitrile, acetone, dimethylformamide and dimethylsulfoxide, has been studied previously (57). The studies of the same complex in two more 80 solvents, such as the sulfolane and hexamethylphosphoramide, were used as a supplement for a series of comparisons with other comparable complexes. Thallium-205 chemical shifts at different 18C6/Tl+ mole ratios are given in Table 15 and illustrated in Figure 17 which show that only 1:1 complex is formed in the two solutions. The relative formation constants have been Obtained as described in APPENDIX 2-A. For comparison purposes, the results of this work and Rounaghi°s work (57) are collected in Table 16. The data show that the formation constant of the complex in hexamethylphosphoramide, log Kf=l.35, is much lower than those in dimethylsulfoxide, water, dimethyl- formamide, sulfolane, acetone, acetonitrile, and nitromethane solutions. These results reflect the much stronger Tl+ ion solvation by hexamethylphosphoramide as compared with other solvents. Of these solvents, hexamethylphosphoramide has highest Gutmann donor number (DN=38.2) but an intermediate dielectric constant (6=30.0). Once again, the results verify that, in the complexation reaction, the donor ability of a solvent plays a more important role than the dielectric constant. The complexation reaction was also studied by carbon-l3 NMR. The data are listed in Table 17. By fitting the vari- ation of the 13C chemical shift versus the TlClOu/18C6 mole ratio (Figure 18), the stability constant Of log Kf= 3.43 i 0.08, was Obtained, which is in good agreement with the value 81 000 5.00 00.0 000 H.0HH 00.5 000 0.00H 00.5 000 0.00H 00.0 000 0.00H 00.0 00 0.500- H0.0 000 0.55H 00.0 00 0.500- 50.H 000 0.000 00.: 00 0.000- 00.H 000 0.500 00.0 05 0.000- 5H.H 000 0.000 00.0 00H 0.0H0- 00.H 000 0.000 00.0 :00 0.0H0- 50.0 000 0.5H0 00.H 050 0.5H0- 00.0 000 0.500 00.H 000 0.H00- 05.0 000 0.000 00.H 0H0 0.000- 00.0 000 0.000 05.0 550 H.000- 00.0 000 0.H50 00.0 H0 0.500- 0 Hvaad A20000 +H0\q Asmvad A50000 +Ha\q 0020 00 .0020 0mm 00 0H oHpmm 0H0: A2 H0.0v 00H0H0\000H :pwzmHHHcm.dmcH8000 H0000 Ho soHpmHnm> 0:0 .0H 0Hnme 82 '100 IOO 8(pp00 200 300 400 l g l l J l L 0 II) 20 130 51) 61) '20 BI) 41) [I8C6] / [TU] Figure 17. Chemical shifts of Tl-205 xg- 1806/Tl+ mole ratio in various solvents. 83 Aoav coconmwmmo 022 00H 00 00H00000 Ammv mocmhmmmmm - 0 h - - 0.0HH0.0HH- 00.0H00.H 0020 - 0 a 5.0H0.000 00.0H00.0 0.0H0.00 - 0H0.0H00.H 0020 - - 0.0HH5.000 H0.0H00.0 - 000.0H50.0 000 0.0H0.00H 00.0H0H.H 0.0H0.005 00.0H00.0 0.0H0.00H- Q00.0H00.0 020 0.0H0.000 00.0H00.0 0.0HH.005 0 A H.0HH.500- 00.0H00.0 00 0.0H0.0H0 00.0H0H.0 0.0H0.505 0 A 0.0H0.50H- 00 A 00 0.0H5.000 00.0H0H.0 0.0H0.005 0 A 0.0H0.50H- 00 A 20 0.0H0.000 00 A 0.0H0.H00 0 A 0.0H0.00H- 00 A 22 “s00vsHH0 H0 000 H50005HH0 00 004 HagmweHH0 H0 000 +AHH.000H000 +HHH.000H<00 +AHH.000HV mpcm>H00 .mpcm>H00 msoH00> 0H AHH.000HHQV 0:0 +AH0.000H<00 .+AHH.000HVAHompHHaMTHmoHsono mcHHHeHH 0:0 000000000 HHHHHnmpm .0H mHnme 84 Table 17. The Variation of 13C ChemicalShiftswmjw- Tl /l8C6(0.04 M) in DMF with AN-d3 as Reference. TlI/l 6(ppm) 0 00 69.95 0 21 69 82 0.36 69.70 0.52 69.62 0.60 69.56 0.69 69.51 0.76 69.48 0.87 69.42 1.00 69.36 1.10 69.35 1.20 69.34 1-37 69.33 1.67 69.32 85 8(ppm) J l l 0 1.0 2.0 3.0 4.0 [11*l/ [18cc] Figure 18. Chemical shifts of C-13 E- Tl+/18C6(0.04 M) mole ratio in dimethylformamide. 86 of log Kf=3.35i0.06, obtained by 205T1 NMR (57). The results clearly show that both 205T1 and 13C NMR techniques can be used for complexation study. However, in general, 205T1 nuclei are a better NMR probe than 13C nuclei because the 205T1 resonance is more sensitive to the change of the envi- ronment of the Tl+ ion. D. Complexation of the Tl+ ion by DA1806 The complexation between DA1806 and the T1+ ion has been previously investigated in this laboratory by Shamsipur (70). At that time, he did not notice the foldover effect (section II-4-A) therefore, incorrect 205Tl chemical shift measure- ments were Obtained. The variations of the 205T1 chemical shift with the DA18C6/T1C104 mole ratio in various solvents are shown in Table 18 and 19. The plots of the 205T1 chemical shift as a function of the DA1806/T1010“ mole ratio are shown in Figure 19. It seems that only 1:1 complex is formed in all studied solvents. In the solvents of weak donor ability such as nitromethane, acetonitrile, acetone and sulfolane, the reso- nant frequency of 205T1 is strongly affected by the addition of the ligand, and the plot (Figure 19) consists Of two straight lines with an intersection at a 1:1 DA1806/T1+ mole ratio. These results indicate the existance of a very stable complex;the lower limit for the formation constants deter- mined by NMR techniques, Log Kf=5, is reported for these 87 00 0.005 00.: 00 0.005 00.: H0 0.005 00.0 00 0.H00 05.0 00 0.005 00.0 H0 5.000 00.0 H0 0.H00 00.0 00 0.005 00.0 H0 0.000 00.0 00 0.H00 00.0 00 0.005 00.H H0 0.000 00.0 05 0.H00 00.0 00 5.005 H0.H 00 0.000 00.0 05 5.000 00.0 00 0.005 00.H 00 5.000 00.H 00 0.000 00.0 00 0.005 00.0 00 0.000 00.H 00 0.000 00.0 - - 00.0 00 0.000 00.0 00: 0.0H0 00.0 - - 00.0 - - 00.0 - - 00.0 0H 0.000- 00.0 0H 0.000- 00.0 00 0.050- 00.0 A0505 A8930 +.E_\.H A0523 2:930 +.E.\.H A0523 A8930 +He\q o< z< Ez . 00 00 m0co>H00 mscH00> 0H 000000 00H; xcH0Eo0 000000 2 00.0 000 0000 0H000 0002-0HH00 HmcHsmgo 000-aaHHHmae .0H 00000. 88 ..1 III I: (I III-(III) II- I I 00 5.005 0H.0 H0 H.005 0H.0 00 5.000 00.0 00 0.005 H0.0 H0 0.005 00.0 00H 0.000 00.0 05 0.505 00.0 H0 0.005 00.0 000 0.500 00.0 50 0.005 0H.0 H0 H.005 00.H 00H 0.000 00.0 00 0.005 00.0 H0 0.005 H0.H 00H 0.H00 00.0 00 0.005 00.H 05H 0.H05 0H.H 00H 0.000 50.H HoH 0.005 0:.H 0H0 0.005 50.H 000 0.050 H5.H 000 H.005 00.H 0.00H 0.005 00.0 000 0.000 00.H 000 0.005 00.H - - H5.0 000 0.5H0 00.0 000 5.000 00.0 - - 50.0 000 H.050 H0.0 - - 00.0 - - 50.0 000 0.000 00.0 050H 0.000 00.0 - - 0H.0 000 0.000 00.0 00 0.HOH 00.0 H0 5.000- 00.0 Asmvaq H50000 +HB\H Aamvaq A00000 +H0\q A0002: A20000 +HH\0 0020 020 000 .0oscH0c00 .00 00000 89 Table 19. Thallium-205 Chemecal Shift-Mole Ratio Data fog 0.01 M TlClOu Complex with DA18C6 in H20 at 24 C. L/Tl+ 0(ppm) A»(HZ) 0.00 - 2.5 21 0.15 7.6 27 0.27 18.3 39 0.53 35.0 42 0.63 40.1 45 0.76 46.5 59 0.90 55.1 78 1.05 63.0 70 1.20 73.2 66 1.41 85.2 71 1.70 95.6 78 2.10 121.4 71 2.76 152.7 71 2.76 152.7 78 3.89 204.0 71 4.50 227.0 71 5.20 252.0 78 5.72 268.7 71 7.00 307.6 71 9.26 364.4 71 .90 O H E 3 3 200 H20 '- w —- 400 '- )\\' - , oOMso I 600 h \‘ . ° 0 . . .NM '- - 1 ° 20' NT," LIL. "' ' 7 800- ‘DMF - 1 1 1 1 1 1 1 0 LC 2.0 3.0 4.0 5.0 6.0 7.0 8.0 [ DA 1806]/ [TU] Figure 19. Chemical shifts of Tl-205 y_s_. DA18C6/Tl+ mole ratio in various solvents. 91 solvents. It is interesting to note that in nitromethane, acetonitrile, acetone and sulfolane solutions all Of the 205T1 chemical shift differences between solvated T1+ ion and the thallium(I) complex are over 1000 ppm which is larger than the maximum spectral width, 722 ppm, on the DA-60 spec- trometer. In these studied systems, we need to shift the detecting window frequently by the procedures described in section II-4-A to avoid the appearance of the foldover effect. The calculated relative formation constants and limiting chemical shifts for the (DA18C6-Tl)+ complex in various sol- vents are listed in Table 16. The data indicate that the stability constants of the (DA1806-Tl)+ complex in various solvents decrease in the order nitromethane, acetonitrile, acetone, sulfolane > dimethylformamide > dimethylsulfoxide > water. This is the same order as shown in the (1806-Tl)+, (DB18C6-T1)+, and (cis-syn-cis-DC18C6-Tl)+ complexes. The results indicate that, even in the complex of the mixed donor crown ether and Tl+ ion, the donor number scale of a solvent shows a more significant role than the dielectric constant. In Figure 19, the data show that the thallium-205 reso- nance shifts downfield with an increasing DA18C6/T1+ mole ratio even in high donor ability solvents, such as dimethyl- formamide and dimethylsulfoxide, which is not the same trend as found with (1806-T1)+ (DB1806-Tl)+, and (cis-syn-cis— DCl8C6-T1)+ complexes. The results indicate that the inter- action force between the Tl+ ion and the ligand is stronger 92 in (DA18C6-T1)+ than in (l8C6-Tl)+, (DBl8C6-T1)+ and (cis- syn-cis-DC1806-Tl)+ complexes, so that even in the high sol- vating solvent the 205T1 chemical shift still shifts down- field. + E. Complexation of the T1 Ion by DT18C6 The complex of Tl+ ion with DT18C6 in nitromethane, ace- tone, acetonitrile and dimethylformamide has been previously studied in this laboratory (57). These studies were extended to three more solvents: sulfolane, dimethylsulfoxide and hexamethylphosphoramide (Table 20). The formation constants Of this complex were compared with those of its analogs, such as (1806-T1)+, (DB18C6-T1)+, (cis-syn-cis-DCl8C6.T1)+ and (DA1806-Tl)+. In dimethylsulfoxide and hexamethylphosphora- mide soultions, the 205T1 chemical shift does not change with increasing DT18C6/T1+ mole ratio (Figure 20) which indicates that no complex is formed. The stability constant of log Kf= 2.66:0.03 for the (DT18C6°T1)+ complex in sulfolane was ob- tained. The complexation between the Tl+ ion and DT18C6 in ace- tonitrile was studied and the measured 205Tl chemical shift at different ligand/T1+ mole ratios are given in Table 20 and plotted in Figure 20. Previously, Rounaghi (57) reported that both 1:1 and 2:1 complexes were formed in this system. After repeated study, we found that their conclusion was incorrect due to Rounaghi's disregard of foldover effect. 93 0.500 05.0 5.500 00.0 0.500 00.0 0.500 00.H 0.000 00.H 0.050 00.H 00 0.0H0 00.0 0.000 00.0 0.550 00.0 50H 0.500 00.0 0.000 00.0 0.050 5H.H 0.000 05.0 000 0.000 00.0 0.000 00.0 0.000 00.0 0.000 00.0 005 0.500 00.H 0.000 00.0 0.000 00.0 0.000 00.0 0500 0.00H 00.H 0.500 00.H 0.000 00.0 0.000 00.0 000 0.HOH 0H.H 0.000 00.0 0.000 00.0 0.000 00.H 000H 0.00 00.0 0.05H H0.H 0.000 00.0 0.000 00.0 0000 H.00 05.0 0.HOH 00.0 0.000 00.0 5.000 05.0 HO0H 0.0 00.0 0.00 H5.0 0.000 05.0 0.000 00.0 000 0.50H- 5H.0 0.0H 00.0 0.50H 00.0 0.000 00.0 00 0.500- 00.0 0.000- 00.0 0.H00- 00.0 As0000 +HH\0 “00054 Heaava +HH\H Heaava +HH\0 Heamvo +Hexg 000 .0 00 00 00:00Hom msoHHm> 0H 000Han 00H; measoo onoHe z H0.0 000 0000 0H0mm 0Hoa-0HH00 HmoHsoco 000-eaHHHcse .00 0Han 94 0000 00 00H00000 2 00.0 0H 000000 00 :0H00000000000 000 0.050 00.0 000 0.050 00.0 000 0.050 00.0 000 0.05: 00.H 000 0.05: 05.0 000 0.050 00.0 000 0.050 00.0 Asmvaq. Asaav0 +He\q 0020 .0000H0000 .00 00000 95 I l f I l -300 _. -2oo\ ' SF 0 0 AC 0 0 -mo- DMS _> 0 AN 0 HMPA 0 ~ _ E Q. 3 IOO- 0 (D 200- i 300 " o ‘1 < u +—O——— 400- ' 0. +— - i 500 _ 7 l l 1 l l 0 LC 2.0 3.0 4.0 5.0 6.0 [DTl8C6]/ [TU] Figure 20. Thallium-205 chemical shifts vs. DT1806/TI.- mole ratio in various solvents. 96 The stability constant and limiting chemical shift obtained from our data are log K = n.16t0.06 and 511m: 388.7:O.3 ppm f respectively. F. Comparison of the Results The stability constants of the Tl+ ion complexes with 1806 and its analogs in various solvents, which were obtained in this work and by previous investigators (10.57.59). are collected in Table 210 The results show that the complex stability decreases in the order (DA1806-T1)+ > (1806.131)+ > (cis-syn-cis-Dolacé-Tl)+ > (DB1806-Tl)+ > (DTlBC6-Tl)+. Previous reports (43.64-66) show that the complexation of macrocyclic polyethers with alkali or alkaline earth ions is weakened appreciably as -NH- is substituted for -O- in the crown ether ring. However, the inverse result is observed for (DA1806-Tl)+ complex as was also found in the (DA1806 °Ag)+ complex (#3). The possible reason may be due to the fact that the basicity of the nitrogen atom is softer than that of the oxygen atom which produces an increase in the bond strength between the soft Tl+ ion and the nitrogen donor atom. The presence of two aliphatic cyclohexo substitutents in cis-syn-cis-DClBC6 increases the rigidity of the crown ether ring causing a drop in the stability of (cis-syn-cis- DC1806°T1)+ as compared with the (1806-Tl)+ complex. In the (DB1806-Tl)+ complex, two benzo rings lend rigidity to the 97 Ammv mocopowmmm Aoav ooCoMmmom mzz om0 as ee0sssme % Ammv mocohm%mm rom0om-w0o-ssm-m0e m0 <-eow0oao hopes: honou scmspso U Q mePwCoo oflhpowamflv psm>aomm o a - - o a No.0umm.0 «.mm o.on smzm o r mo.oumm.m so.oumm.0 o a u0o.oumm.0 m.mm o.ms omsm es0.owmm.o 0o.ouom.o m:o.osss.m mmc.ouom.0 meo.ousm.m o.mm m.ms omm so.owm0.0 mo.owmm.m oo.oums.m mo.oun0.m emo.owms.m 0.0m 0.0m mam mo.ouoo.m m A so.owo0.: so.owso.s so.oumm.s m.:0 o.~: am 00.mvmm.osem.0 so.oum0.m m A m A 00.0vmo.oumm.m em A o.s0 5.0m Us ee.ese0.e m A m A m A em A 0.:0 e.wm as Um A m A m A m A cm A m.m m.mm 22 +0e.mom0ea +0e.eom00om 0m me0 .mpco>aom mSOflhm> CH moxoamsoo AHVESwHHmce map go mpcMszoo_mvHHHnmpm .HN wands 98 ligand and withdraw electrons from the basic oxygen donors, thus decreasing the bonding between the Tl+ ion and the li- gand. The aliphatic cyclohexo substituent contained in cis- syn-cis-DClBC6 is more flexible than the benzene substituent in DB1806, so that the stability constant of the (cis-syn- cis-DClBCé-Tl)+ complex is larger than that of the (DB18- Cé-Tl)+ complex. In the same solvent, the stability constant of the (DT1806-Tl)+ complex is smaller than those of the other four complexes. Two factors seem to be important in causing this drop of the stability constant. The first factor is that the structure of the DT1806 in solution may be the same as in the solid state which directs its two sulfur atoms away from the cavity to make the cavity too small to fit the Tl+ ion exactly. The other factor may be that only the outwardly turned sulfur atoms of DT1806 participate in coordiantion with the T1+ ion which is the case of PdClzoDT18C6 complex (Figure 8). Pearson (128) has suggested that the interaction of metal ions and ligands can be explained in terms of their "hard- ness" or "softness". This principle states that "Hard acid prefer harder bases". From the above discussion, it is ob- vious that the interaction force between S-Tl (soft base- soft acid) is stronger than that between O-Tl (hard base- soft acid). Although the thallium(I) ion prefers binding 99 with the two sulfur atoms on DT18C6 rather than with the oxygen atoms on 18C6, a decrease in the stability constant is observed for the (DT1806-Tl)+ complex. The possible rea- son may be due to the fact that there are six O-Tl coordi- nation bonds in the (1806-Tl)+ complex but only two S-Tl bonds in (DT1806-Tl)+. A total interaction force of six weak O-Tl bonds may be larger than the sum of two strong S-Tl bonds. The data collected in Table 21 clearly indicate that the solvent plays an import role in the complexation process. It is interesting to note that in acetone DB1806 forms both 1:1 and 2:1 (ligandzmetal) complexes with the Tl+ ion. In all of the other systems studied, only the 1:1 complex has been found. The results show that the stability constants of five studied complexes in various solvents generally de- crease with increasing Gutmann donor number of the solvent. It can be concluded that, in a complexation reaction, the donor ability of a solvent plays a more important role than the dielectric constant. When the complexation reaction takes place in a strongly solvating solvent, such as dimethyl- sulfoxide or hexamethylphosphoramide, the solvent molecules exhibit a strong competition with the ligand for the coordi- nation sites of the cation and produce a decrease in the complex formation constant. The stability constants of five complexes in various solvents decrease with increasing Gutmann donor number in the order nitromethane > acetonitrile > acetone > 100 sulfolane > dimethylformamide > water > dimethylsulfoxide > hexamethylphosphoramide. Ion pairing has been prOposed as a possible factor to affect chemical shift for 7Li (129,130), 23Na (103,10u) and 133Cs(lO5) NMR. Because Li+ and Na+ have quite small ionic radii compared to Tl+ or Cs+, it might be expected that solvation would be more important in determining the shift for the Li+ and Na+ ions. The Cs+ and Tl+ ions have larger ionic radii and are less strongly solvated. In this case, ion pairing would be expected to be much more important, especially in a nonaqueous solvent with low dielectric con- stant. Figure 21 shows that the thallium—205 chemical shift range of the solvated Tl+ ion in different solvents is N900 ppm. In general, the 205T1 resonance shifts upfield in low solvating solvents such as nitromethane, sulfolane, acetone, and acetonitrile, but shifts downfield in high solvating sol- vents such as dimethylformamide, dimethylsulfoxide and hexa- methylphosphoramide. It is also interesting to note that in low solvating solvents, such as nitromethane, sulfolane, acetone and aceto- nitrile, the limiting 2°5Tl chemical shifts of (Tl-1806)+. (TloDB1806)+ and (DClBC6-Tl)+ complexes are downfield compared with the solvated Tl+ ion but they shift upfield in highly solvating solvents, such as hexamethylphosphoramide, dimethyl- sulfoxide, dimethylformamide and water. When complexation reactions take place in a low solvating solvent, the ligands play an important role in determining the electron density + around Tl+ ion. In the complexes (1806-Tl)+, (DB1806-Tl) and -I+OO " -2004 8(ppm) 600- 800- l—DMSO - HMPA 1000 J Figure I 21. 1806 F SF AC _. NM :IAN _:_ DMF __ HMPA DMSO 101 Dclgco DMSO AC C SF :._'_ NM __ AN DMF Dslgco :'SF : DMF AN DA]. 8C6 1r 1 TI Tn F110. DMSO AN SF DMF H O Thallium—205 chemical shifts of solvate DT}_§306 bDMF —NM —AC SF AN Tl+ ion and the limiting chemical shifts of (T1 -Crown) complexes. 102 (cis-syn—cis-DCIBCé-Tl)+, the electron density of the Tl+ ion is enhanced by the encircling electronegative oxygen atoms, which results in a downfield shift. In a highly solvating solvent, the Tl+ ion is enclosed tightly by the solvent molecules. This arrangement causes extensive sp hybridization (5d10 68p) and result in enhanc- ing the electron density of the Tl+ ion greatly. When a complexation reaction takes place, the ligand molecule will replace the solvent molecules occupying several coordination sites around the Tl+ ion. In general, crown ether molecules are more rigid than solvent molecules, which will create several vacancies around the Tl+ ion as the complex is formed. Some of these vacancies are too small to accommodate a single solvent molecule. Therefore, in the complex, the electron density around the Tl+ ion will be less as compared with the solvated Tl+ ion inducing an upfield shift. However, in all of the solvents studied, the limiting chemical shifts of (Tl-DA1806)+ and (Tl-DT1806)+ move down- field compared with the solvated Tl+ ion. A possible reason may be due to the fact that the thallium(I) ion is a soft acid which may prefer to coordinate with sulfur and nitrogen atoms (soft base) rather than with oxygen atoms (hard base). The electron density around the Tl+ ion may be increased by the effect of these acid-base coordination bonds which will induce a downfield shift. As shown in Figure 21, the limiting chemical shifts of 103 all five complexes studied in various solvents span a 200 ppm range, which clearly indicate that in all of the comp— plexes, the thallium(I) ion is only partially encapsulated, and the solvent molecules and counter ions can still in- teract with the vacant coordination sites of the complexed Tl+ ion. The data summarized in Tables ll, l4, 15 18 and 20 clearly show that in some solvents, the linewidth of the 205T1 resonance broadens dramatically as the ligand/Tl+ mole ratio varies between 0 and l. The examples of 205T1 NMR spectrum with different linewidths are shown in Figure 22. The possible reason for this line broadening is intermediate exchange of the Tl+ ion between solvated and complexed sites. In these cases, the temperature was decreased to make the lifetime at each site (1A and 1B) become large, with the interaction time (1) increased according to the following equation(131). .1 I (3.12) A A "13 q where TA and TB are the lifetimes of solvated Tl+ ion and complexed Tl+ ion respectively. If TA and TB become large enough to make 1 be larger than the NMR time scale, the broad line will be resolved into two separated lines which repre— sent the complexed and solvated Tl+ ions. The condition required to separate two resonance lines is 104 am at Nm Nm Nm Nm are -55000 new no mzz 0v %o mhvcm c. souww 0 p 03ocfl .mcpc. mm ohsmflm moa mmm cmm0 H j 105 T > w Av (3.13) where Av is the frequency (Hz) difference between sites A and B. However, in our systems, the 205T1 linewidth in- creased with decreasing temperature, but the resonance could not be resolved into two separate lines. In some case (Table l# and 15), the resonance of 205T1 became too broad + to be measured when the ligand/Tl mole ratio was around 0.5. GMMERIV THERMODYNAMIC STUDIES OF THALLIUM(I) SALTS WITH lB-CROWN-é AND ITS SUBSTITUTED ANALOGS IN SEVERAL SOLVENTS 106 I. Introduction The thermodynamic properties of macrocyclic complexes have been under active investigation during the past decade. It seems, however, that most of the attention has been fo- cused on alkali cation complexes. Few thermodynamic studies have been reported for the complexation of the Tl+ ion with 18-crown-6 and its substituted analogs. Izatt and co-worker (10) have determined the thermodynamic parameters (AGE, ASS, and AH:) for the complexation of the T1... ion with the crown ethers 1806, D01806 and DT1806 (28), in aqueous solution by calorimetric techniques. They found that the complexation reactions of (1806-Tl)+, (DClBCé-Tl)+ and (DT1806-Tl)+ are all enthalpy stabilized (AH: < 0) but entropy destabilized (as: < o). The present work reports the use of 205T1 NMR to study thallium(I) complexation with the crown ethers 1806, DBlBCé and DT1806, in several nonaqueous solvents at different tem- peratures, in order to show how the thermodynamic parameters for the complexation reaction are affected by the nature of the medium, the cavity size and the substitution of two oxygen atoms by two sulfur atoms. 2. Thermodynamic Study of The Complexation of the Tl+ Ion by 1806. 107 108 The complexation of the Tl+ ion by 1806 in various sol— vents has been studied and discussed in detail in section III-3-C. In order to have a better understanding of the thermodynamic behavior of this complexation reaction, we have studiedthe complexatiGncd‘lBCé with thallium(I) perchlorate (0.01 M) in sulfolane and dimethylformamide solutions at various temperatures. The data obtained from these studies are collected in Tables 22 and 23. In all cases studied here, only one thallium-205 resonance signal was found which indicate a fast exchange between the complexed and solvated Tl+ ion. As shown in Table 22, for both solvents, the line- width of 205T1 resonance become broad as the ligand/Tl+ mole ratio is varied between 0 an and 1. It decreases gradually as temperature is increased, The possible reason is due to intermediate exchanges existing between two Tl+ sites (i:g; the solvated ion and complexed ion) at low temperature. Figures 23 and 24 show the variation of 205m chemical shifts as a function of 1806/Tl+ mole ratio in sulfolane and di- methylformamide at various temperatures. It is obvious that the curvature of the plot decreases with increasing tempera- ture which demonstrates the formation of a weaker complex at higher temperature. Therefore, in both solvents, the com- plexation of the Tl+ ion by 1806 is an exothermic reaction. In both solvents the plots show a clear break around the mole ratio of 1:1 (metal ion:ligand), which indicates that a 1:1 complex is formed. In sulfolane the NMR resonance of th Tl+ 109 00 0.000- mm 0.000- mm 0.000- 00.0 mm 0.000- 00 0.000- 0: 0.000: 00.0 mm 0.000- a: 0.000- mm 0.000- 00.0 mm 0.000- mm 0.000- 00 0.000- a0.0 as 0.000- mm 0.000- 000 0.000. 00.0 :00 0.000- 000 0.000- 00m m.m0m: 00.0 um0 m.mm0- nmm m.:om: mm: m.p0mn 00.0 000 0.000- mam 0.000- 000 0.000. 00.0 000 0.000. cmm 0.000. 000 0.000- 00.0 0mm 0.0mm- can 0.000- 000 0.0mm- 00.0 mm 0.000- mm 0.000- 00 0.000- 0 Anmv>< Asmmvo Anmvad Aacmvo Anmv>< Asmmvo 0000 .mexa 000: 0000 .mwpzpwgoQEoe wSowhm> #0 mm :0 puma pp“; 000as00 00000s 2 00.0 000 0000 00000 0002-00000 0000s000 momusa0000na .NN manma 110 mm 0.000- mm 0.000- on 0.000- 00.0 mm 0.000- 0: 0.000- 00 0.000- 00.0 m: 0.000- 00 0.000- 00 0.000- 00.0 mm m.m00: no m.000n ms m.0m0n 00.0 mm 0.000- ma 0.000- 00 m.m00u 00.0 mm o.ma0n on o.mm0n mm 0.000- 00.0 mm 0.000- mm. m.0m0- 000 0.000- 00.0 00 0.000- am0 0.000- 000 0.000- 00.0 000 0.000- ~00 0.000- 000 0.000- 00.0 000 0.000. 000 0.000- mm 0.000- 0n.0 mm 0.000- m.m:m- mm m.m:m- 0. Anmv>< Aemnvo Aumv>< Asamvo Aumv>< Aemnvo 0000 00am 4. 0000 +0B\0 .Uoscwpaoo .Nm wands 111 0.00 0.000- 0.00 0.000- 0.00 0.000- 00.0 0.00 0.000- 0.00 0.000- 0.00 0.000- 00.: 0.00 0.000- 0.00 0.000- 0.0: 0.000- 00.0 0.00 0.00 - 0.00 0.000- 0.00 0.000- 00.0 0.00 0.00 - 0.00 0.000- 0.00 0.000- 00.0 0.000 0.00 . 0.000 0.00 - 0.00 0.000- 00.0 0.000 0.00 I 0.000 0.00 - 0.000 0.00 . 00.0 0.000 0.00 - 0.000 0.00 - 0.000 0.00 - 00.0 0.000 0.0 0.000 0.0 - 0.000 0.00 . 00.0 0.000 0.00 0.000 0.00 0.000 0.00 00.0 0.000 0.00 0.000 0.00 0.000 0.00 00.0 0.00 0.000 0.00 0.000 0.00 0.000 .0 Aumv>< “agave Anmv>< Asmmvo Anmv>< Aemmvo 0000 0000 0000 +05\0 d .moQSPmquEoB m30000> Pm mzn :0 puma £903 on009000. 0000s 2 00.0 000 000m 00000 0002-00000 00005000 000-00000009 .00 00000 112 0.0: 0.00 - 0.00 0.00 0.00 0.00 00.0 0.00 0.00 n 0.00 0.00 0.00 0.0 00.: 0.00 0.00 . 0.000 0.00 0.00 0.00 00.0 0.00 0.:: . 0.000 0.00 0.00 0.0m m0.m 0.000 0.00 . 0.000 0.00 0.00 0.00 00.0 0.00 0.0 I 0.00 0.00 0.00 0.00 00.0 0.00 0.0 0.00 0.0 0.00 0.00 00.0 0.000 0.00 0.000 0.: 0.000 0.00 00.0 w.300 m.mm w.:m0 o.wm 0.000 0.mm mp.o 0.00 0.000 0.00 0.00 0.000 0.00 00.0 0.00 0.000 0.00 0.000 0.00 0.000 00.0 0.00 0.000 0.00 0.000 0.00 0.000 00.0 0.0530 “0:va0 05.805 200030 23.3 >4 A803: 0000 0000 0000 +0B\0 .000000000 .00 00000 113 —280 ‘ 1 j l T l . “F -260 -1 —2£&O ‘ - “-220 r- E -1 O. O. *- k V 9 L n__. O —1 ‘D ' - 31 C -200 - - \ 0 + e_ “3 -180 b ‘ O k— ; 66 q " \n N 77 _ ‘N -160 _ 93 .- 1 I l n l O 1.0 20 3.0 [laced/[n+1 O Figure 23. Chemical shifts of Tl-205 vs. 1806/T1C10 (0.01 M) mole ratio in sulfolane at different tem eratures. 114 -120 l I u T l + —‘——-——*-—'— 21100 e #4: 43 *‘ 38 -100- o/xr”fflc é? _ :r—fi 5 A o u 79 . . 93 -60"' A o - -20 . _. A E o O- 20 _ CL V 00 6C _ 100 , 0 1110 «- 180L J I l I l O 1.0 2.0 3.0 4.0 5.0 6.0 [0ch / [TU] Figure 24. Chemical shifts of 205T1 vs. l8C6/TlClO (0.01 M) mole ratio in DMF at various temperatur s. 115 ion shifts downfield with an increasing 18C6/Tl+ mole ratio at various temperatures but it shifts upfield in dimethyl- formamide. Formation constants and limiting chemical shifts of the (18C6-Tl)+ complex in sulfolane and dimethylformamide at various temperatures were computed and the results are listed in Table 24. As expected, the stability constant varies in- versely with the temperature. The thermodynamic parameters AGE, AH: and ASS were cal- culated from the temperature dependence of the equilibrium constant according to the following thermodynamic expression: r _ O 0 -RT ln hf AGO TASc O O an = AHc + Ase (4.1) f RT R Van't Hoff plots of In Kf versus -%- for the (1806-Tl)+ com- plex in sulfolane and dimethylformamide are shown in Figure 29. The thermodynamic parameters of the complexation reac- tion were obtained by fitting ln Kf ls. l/T with a linear least squares program. The enthalpies (AHg) and the entro- pies (ASE) of the complexation were obtained from the lepes and interceps of the plot. These results with the AG: values (at 30°C) were collected in Table 24. These data indicate that, in sulfolane, the (18C6-Tl)+ complex is enthalpy and and slightly entropy stabilized, whereas, the same complex 116 0.0 0 0.00 I 00.0 0 00.0 00 00.0008\00o 00.0 H 00.00- nwmq m.m H 0.00 n 00.0 0 :0.~ 00 0.0 0 0.00 - 00.0 0 00.0 00 0000\0000 00.0 H 00.0- "“04 0.0 0 0.000- 00.0 0 00.0 00 0.0 H 0.000- 00.0 0 00.0 00 0000\000 00.0 0 00.0 "000000w04 0.0 H 0.000- 00.0 H 00.0 00 020 0.0 0 0.000- 00.0 H 00.0 00 00.000s\000 00.0 0 00.0 "004 0.0 H 0.000- 00.0 0 00.0 00 0.0 0 0.000- 00.0 H 00.0 00 0000\0000 00.0 0 00.0- ammo 0.0 H 0.000- 00.0 H 00.0 00 0.0 H 0.000- 00.0 0 00.0 00 0000\000 00.0 0 00.0- "00000vw04 0.0 H 0.000- 00.0 H 00.0 00 00 mumpc8mpmm 0080800080009 A8mmv80ao 0M meg Aoovcpsvmuom8wa 080>Hom .020 000 00 00 N000500 000.00000 00 000000 00008020 w800080q 680 mpzmpmzou GOHPMEMom map Mo comm unomom 00300000809 .dm mamas 117 in dimethylformamide is ethalpy stabilized but entropy des- tabilized. The measured enthalpy change (AHg) for a complexation reaction in solution reflects the energy change between reac— tants and products which include (a) the bond energy of the cation-donor atom bonds (b) the solvation energy of reactants and products (iLg., ion solvent interaction,ligand solvent interaction and complex solvent interaction). Several fac- tors contribute to ASS which include (1) ligand and cation desolvation, (2) Solvation of the complex,(3) change of com- plex formation from cation and ligand, (4) internal entrOpy change of the ligand upon complexation caused by configura- tional entropy changes between reactants and products. Among these four factors, the configurational entrOpy change of the ligand upon complexation may be more pronounced as compared with the other factors. The thermodynamic data collected in Table 24 show that quite different AS: values are observed in sulfolane and dimethylformamide. In sulfo- lane, the overall entropy change is small which shows that the rigidity of solvated and complexed ligand is almost the same in this solvent. However, in dimethylformamide, a neg- ative entropy change indicates that the complexed 18C6 is more inflexible than the solvated 1806. The AH: value is also solvent dependent because the solvation energies for the Tl+ ion , the ligand and the complex vary with the solvent. 118 3. Thermodynamic Study for the Complexation of the Tl+ Cation by DB1806. The thallium-205 chemical shift-mole ratio data for the (DB1806-Tl)+ complex in sulfolane and dimethylformamide at various temperatures are listed in Tables 25 and 26. The data are plotted in FiguresZS and 26. In sulfolane the T1- 205 resonance shifts downfield with an increasing DB1806/Tl+ mole ratio but an upfield shift of the 205T1 resonance was observed in dimethylformamide. The formation constants and limiting chemical shifts of the (DB1806-Tl)+ complex in sulfolane and dimethylformamide at various temperatures were calculated and the results are listed in Table 27. The limiting chemical shift difference between 31°C and 95°C in sulfolane is 10 ppm and 110 ppm in dimethylformamide. The possible reason may be that, at high temperature. the complex becomes more flexible and the high solvating solvent can approach closely to the Tl+ ion and change the electron density around the complexed thallium(I) ion inducing a large chemical shift change. The Van't Hoff plot of In Kf versus -%— is shown in Figure 29 and the calculated thermodynamic parameters are presented in Table 27. In both solvents, the complexation reaction is enthalpy stabilized (AH: < 0) but entrOpy desta- bilized (AS: < O), and the variation of enthalpy and entrOpy 119 0H 0.000- 0s 0.000- 0H mum00- m0.: 0H 0.000- 0 0.000- m0 H.200- oo.m 0H H.H00- mm H.000- m0 m.s00- sm.H 08 0.000- m0 0.000- m0 0.300- 00.0 m0 H.800- 00 8.000- H: c.000- so.H m0 0.0m0- H4 m.Hm0- H: 0.mm0- 00.0 m0 c.0m0- a: m.os0- 00 0.0:0- 0m.o mm 0.3:0- mm H.wdm- :20 m.HmN- mm.o 0H n.mm0- m0 0.000- m0 0.000- 00.0 Aumv>< A8vao Asmv>< n8nmvo Aumvad A8mmvo Ha\q comm coma seam + .0083P0H0Q809 mSOHH0> #0 mm 8H oomamm npws xmaasoo :oaoae s Ho.o new 0000 oHp0m macs-pmaam H0oHsezo mo0-ssHHH0ne .m0 0Hn0a 120 0H 0.300- 0H n.000- 0H H.0H0- m0.: H0 n.0a0- H0 m.0fi0- m0 0.0H0- 00.0 H0 0.000- m0 c.000- m0 0.0H0- :0.H m0 0.000- 00 0.000- H: o.H00- 00.0 mm m.m00- 0: 0.m00- as 0.800- 80.0 0: m.s00- mm H.m00- as 0.000- 00.0 mm 0.000- 0: 0.000- 0: 0.:m0- 0m.o 00 0.mm0- mm 0.000- 00 0.020- mm.o 0H m.o:0- 0H 0.3:0- 00 0.0m0- oo.o A0530 8930 #0515 8830 3530 Edge as a seam some so: + \ .peasflpcoo .m0 manna 121 ow m.m0 - mm m.0: - 0: o.m0 - 00.0 0: 0.0 mm 0.00 - mm 0.0: - mm.0 00 0.00 00 0.0 00 0.00 - 00.0 on 0.00 mm 0.00 00 0.0 00.0 m: m.m0 0: 0.00 00 0.0: 00.0 00 0.00 00 0.00 00 0.00 0m.o 00 0.00 00 0.000 00 0.000 00.0 Asmv>< 000000 - 000004 000000 000000 000000 -. 00\0 000m 0000 0000 + 0 .000390009809 000000> #0 mac :0 womeQ 0903 x000000 00000 2 00.0 000 0000 00000 0002-0000m 00000000 000-00000000 .00 00000 122 00 0.00 00 0.00 00 m.o 00.0 00 0.00 0: 0.00 00 0.00 00.0 00 0.00 on 0.00 00 n.00 00.0 0: 0.00 00 0.00 00 0.00 00.0 00 0.000 00 0.000 :0 0.00 00.0 00 0.000 00 0.000 00 0.000 00.0 m0 n.000 m0 :.m00 m0 0.000 00.0 005040 08003 0 020:4 A8003 0 00530 080030 -.. 0000 0000 +00\0 .000000000 .00 00000 -100 -50 8-(FafDrT1) 50 100 120 Ifiigmure 123 I r T I 7 i 2u°c ‘ no ‘ / 52 b 6n . . 79 o '2 r - 1 1 I 1 l 1 o 0.5 1.0 1.5 2.0 \ _ 2.5 3.0 [DBIBij/fr U] 25. Chemical shifts of 01-205 vs. DBlBC6/Tl+(0.01 M) mole ratio in DMF at various temperatures. 124 l U j I I -270 -260 -250- A E Q. a. V —2L-o no -230 0. 0 0, 31°C . ~—O—- 004~—— 45 220 9“ _ u. 0 N c K 58 . . 71 83 95 '210 1 I l l l o 1.0 2.0 3.0 u.o 5.0 [DB-scej/ [TU] Figure 26. Chemical shifts of Tl-205 vs. DB1806/Tl+(0.01 m) mole ratio in SF at various temperatures. 125 0.0m H 0.00 - 00.0 0 00.0 00 00.0000\000 00.0 H 00.0- "M00 0.00 H 0.00 - 00.0 H 00.0 00 0.00 H 0.000- 00.0 H 00.0 00 o 0000\0000 00.0 0 00.0- "004 0.00 0 0.000- 00.0 H 00.0 00 0.0 H 0.000- 00.0 H 00.0 00 O 0000 00 0000\000 00.0 0 00.0- "004 0.0 H 0.000- 00.0 H 00.0 00 000 0.0 H 0.m00- 00.0 H 00.0 mm 00.0000\000 00.0 0 00.00- n wmq 0.0 0 0.000- 00.0 H 00.0 mm m.o H 0.000- 00.0 H mo.m 0m .- o 0000\0000 00.0 + 00.00- "004 0.0 0 0.000- 00.0 0 00.0 00 0.0 0 0.000- 00.0 0 00.0 00 o 0000 00 0000\000 00.0 H 00.0- "004 0.0 0 0.000- 00.0 H 00.0 00 00 0000080000 0080800080009 080008000 MM 000 0000 00500000809 080>00m .020 000 00 00 U000000 000.0000000 00 000000 00008000 08000800 080 008000800 800008000 000 00 0080080000 00300000800 .00 00009 126 values is much dependent on solvent. The entrOpy destabili- zation of the complex may be due to a change in the ligand configuration entrOpy. Dibenzo-lB-crown-6 in the free state may be more flexible than in a complexed state because it . + . becomes more ordered as it forms a complex With the T1 ion. + 4. Thermodynamic Study for the Complexation of the T1 Cation by DT1806. The effect of the temperature on the Tl-205 resonance for the (DT1806-Tl)+ complex was determined at different DT1806/ Tl+ mole ratios in acetone and sulfolane. Thallium-205 chem- ical shifts measured at different temperature are listed in Table 28 and 29. The plots of the 205T1 chemical shift versus DT18C6/Tl+ mole ratio at various temperatures are shown in Figure 27 and 28. In both solvents, at all studied temperatures, the thallium-205 resonance shifts downfield with an increasing DT18C6/Tl+ mole ratio, while the curvature of the plot increases with decreasing temperature indicating the formation of more stable complex at lower temperature; In the case of the (DT18C6°Tl)+ complex in acetone, as the studied temperature is as low as ~310C, the mole ratio plot consists of two straight lines intersecting at a 1:1 ratio (Figure 27) which clearly demonstrates that only the 1:1 complex is formed. At -3l°C. -9°C and 1°C, when the ligand/Tl+ mole ratio varies between 0 and l, the 20,5Tl 127 00.000 00.000 00.000 00.000 00.000 00.000 00.000 00.0 00.000 00.000 00.000 00.000 00.000 00.000 00.000 00.0 00.000 00.000 00.000 00.000 00.000 00.000 00.000 00.0 00.000 00.000 00.000 00.000 00.000 00.000 00.000 00.0 00.000 00.000 00.000 00.000 00.000 02.000 00.000 00.0 00.000 00.000 00.000 00.000 00.000 00.000 00.000 00.0 00.000 00.000 00.000 00.000 00.000 00.000 00.000 00.0 00.000 00.000 00.000 00.000 00.000 - - 00.0 00.00 00.00 00.00 00.000 00.000 - - 00.0 00.0- 00.0 00.00 00.00 00.00 - - 00.0 00.000- 00.000- 00.000- 00.000- 00.000- 00.000- 00.000- 00.0 0.00 00 0.00 0.00 0.00 0.0 0.0- 00 0309 #0 9\.0 .000300000809 080000000 00 00 80 000090 00 00800000 000 80 02 00.00 000009 000 0000 00000 00008000100000.0002 .mm 00009 128 00 0.000 000 0.000 00 0.000 00.0 000 0.000 000 0.000 000 0.000 00.0 000 0.000 000 0.000 000 0 000 00.0 000 0.000 000 000 000 000 00.0 000 0.00 000 0.000 0000 0.000 00.0 000 0.00 000 0.000 000 0.000 00.0 000 0.00 - 000 0.00 0000 0.00 00.0 000 0.00 - 000 0.00 0000 0.00 00.0 000 0.00 - 000 0.00 0000 0.0 00.0 00 0.000- 000 0.000- 000 c.000- 00.0 00 0.000- 00 0.000- 00 0.000- 00.0 0000>< As 000 0000>< 000000 000000. 000000 00\0 0000 0000 + .000500000809 050000> 00 mm :0 000090 0003 0009000 000000 2 00. 0 000 0000 00000 0002-00000 00000000 000-20000000 .00 00000 129 1!‘\ J o.mna Hm H.mom we d.NNN mm.d Hofi 0.5m mma n.mmfi mHH m.me mm.m an m.:: mud m.00H mmm H.mNH :m.m Hofi B.HH mmfi m.mo mmfi m.mn om.H on m.wm I 50H 0.0m me :.m: m:.H mmH :.om I mma :.mm I med H.@ I oH.H moH m.mm I mmfi :.mm I 20H m.mm I om.o mm w.:oHI mmfi m.om I mmfi N.mm I mn.o on m.mNHI mofi N.HoHI “Ha m.mm I mm.o om n.mmHI :2 o.aomI we :.mmHI uH.o Hm o.mmmI “a m.o:mI 5H m.m:mI oo.o Anmv>4 Asmmvo Aamv>< Aemmvo Aumv>< Asmmvo oomoa comm comm +Hs\q .UmscfiPCoo .mm wands 130 I 1 I l 1 1 -200 a 40°C a 30 -100 - ‘ 28 9 20 D 11 I ‘ 1 ’*\ \ - '9 E o - ' r31 0. .0. (D 100 _ 200 _ 300 r- ______‘___,_ 1 1 1 O 2.0 4 O 6.0 [DTIBCSJ/ BU] Figure 27. Chemical shifts of 205T1 vs. DT1806/T1+(0.0l m) mole ratio in AC at different temperatures. 131 7 T 1 l 1 -300.- - "200*- »\ -I “100_ \. c— \I A . E 0 CL 0. _ D— ' 0 V (O 100_ . - ‘ 109°C zooP . , _ o 92 85 74 300_ ° us _ o 31 l n I l l O 1.0 2.0 3.0 LI.0 5.0 [DT18C6]/[Tl+] Figure 28. Chemical shifts of 205T1 vs. DT18C6/T1+(0.0l m) mole ratio in SF at different temperatures. 132 resonance becomes too broad to be measured on our DA-6O NMR (Table 28). The formation constants and the limiting chemical shift of the (DT18C6-Tl)+ complex at various temperatures in ace- tone and sulfolane were calculated as explained previously (APPENDIX 2-A) and are tabulated in Table 30. Plots of 1n Kf versus -%- for these data are shown in Figure 29 and the cor— responding AHS and ASS are shown in Table 30. Thermodynamic parameters indicate that, in acetone and sulfolane solutions, the complex is enthalpy stabilized but entrOpy destabilized and AH: and AS: values vary with the nature of the solvent. The entrOpy destabilization of the complex (ASS < 0) may be due to the fact that 1806 is more flexible uncomplexed than + when complexed to T1 ion (configurational entropy). 5. Comparison of the Thermodynamic Parameters Thermodynamic parameters obtained for complexing of the Tl+ ion by 1806, DB1806 and DT18C6 in several nonaqueous sol- vents are listed in Table 2h, 27 and 30. It is interesting to note that the thermodynamic data in all systems except for the (1806-Tl)+ complex in sulfolane show that the com- plexation reaction is enthalpy stabilized (AH: < 0) but en- trOpy destabilized (ASS < 0). These may due to a change in both the Tl+ ion and ligand from a loose structure in the free state to a "rigid" structure in the complexed state mo.maofi\HmO ummfl . maofi\amx uwmq . maofi\fimm "mad “mH myopmswhwm 0H8msnooEH¢zP How PHQS one .8 ' . .. V1 #3.- 133 n.0H H m.nan «0.0 H mn.a noH nn.o H nn.m I ammo n.0H H o.Hnn No.0.H 00.H m0 5.: H 5.0:n H0.0 H oo.m no nH.o H H0.mI uwmq 0.0 H n.omn No.0 H 0H.m an m.0 H o.mnn no.0 H 2:.m no BH.0 H n0.nI "Aooonvwoq 0.n H 0.0:n no.0 H oo.m an em 0.H H n.0Hn 30.0 H om.m 0: o.H H «.man 30.0 H :o.n on mm.o H nm.HHI ummq 0.0 H m.0Hn no.0 H no.n mm H.H H n.an 30.0 H mm.n 0m 00.0 H H0.NI uwm< 5.0 H n.0Hn 30.0 H H:.n HH 0.0 H m.pon 00.0 H oo.n H HH.0 H om.oI "Aooonvwo< H.H « m.non NH.0 H no.n 0 I o< wpopoemnmm AEQQVSHHQ mu won AoovoHSHMHoQEmB Hzo>aom oHstnooenmne Hwoflsono MCHHHEHA and mHQMHWMMUUMMHmwewwmxwmmmmw “wwwmmwmwwawhwmmmwmwmm .om wanna 134 (E) (A) 10*- —( l l l 2.6 3.0 3.4 3.8 l/T x 103 (A) 1806-T1+ in SF (D) DT1806-T1+ in SF (B) 1806~T1+ in DMF (E) D31806~T1+ in SF (0) DT1806-T1+ in AC (F) DB18Cé-Tl+ in DMF Figure 29. A plot+ of ln K vs. l/T for the complexation of the Tl+ ion Nth 18C6 and its analogs. 135 inducing a negative entrOpy change. Generally, in the same temperature range, the limiting chemical shift difference in a high solvating solvent is larger than that in a low solvating solvent. This may be due to the fact that, at high temperature, the complex becomes more flexible to allow high solvating solvent molecules to approach the Tl+ ion and affect the electron density of Tl+ ion inducing a larger limiting chemical shift ragne. At the present time, the literature information on the interaction of solvent molecules with ligands is quite sparse, additional studies on ligand-solvent interactions are re- quired before the thermodynamic data can be fully understood. CHAPTER V THALLIUM-205 NMR STUDY OF THE TONIC SOLVATION AND COMPLEXATION OF THALLIUM(I) ION IN MIXED NONAQUEOUS SOLVENTS 136 1. Introduction The behaviour of electrolytes in solutions depends pre- dominantly on ion-ion and ion-solvent interactions. The former interaction is,in general, stronger than the latter. Only in a solvent with a high dielectric constant at low solute concentrations, where the salt is completely dis- sociated, can the ion-ion interactions be neglected. In this case, ion-solvent interactions become more important. Ion—solvation has been treated much more frequently in pure aqueous or non-aqueous solvents than in mixed solvents. It is interesting to see how far the solvation of ions in mixed solvents can be explained in terms of the ionic behaviour in the pure medium. Although solvent-solvent interactions are much weaker than ion-solvent interactions, they must be taken into consideration. Therefore, ion solvation has been studied in binary solvent mixtures. While the solvation of thallium(I) ion in various highly solvating mixed solvents has been studied extensively (101, 107-110), the solvation of the T1+ ion in the mixed solvents of low solvating and high solvating power has not been pre- viously reported. Investigations of the complexation of some macrocyclic ligands with the alkali and alkaline earth cations in mixed solvents have been restricted to water/meth- anol systems by the use of the calorimetric technique (12). 137 138 Complexation of the Cs+ ion by several crown ethers and cryp- tand-222 in nonaqueous mixed solvents have also been studied by l330s NMR by Rounaghi (129). We were interested in studying both thallium(I) salts and thallium(I) complexes in mixed solvents in order to see how the nature of the medium affects the ion solvation and the stability of crown complexes. In this chapter, we describe preferential solvation studies of the T1... ion in several mixed solvents such as NM/DMSO, AN/DMSO, PC/DMSO, THE/DMSO, HMPA/DMSO, DMF/DMSO, AN/DMF and HZO/DMF. A study of the Tl+ ion complexed by macrocyclic ligands, such as DA1806 and DT18C6, in DMF/H20 and DMF/AN mixed solvents respectively, is also reported. 2. Preferential Solvation of the Thallium(I) Ion in Mixed Solvents The preferential solvation of the Tl+ ion was studied in several binary solvent systems by the NMR technique. Thallium-205 chemical shifts were measured as a function of solvent composition in a binary solvent system at 24°C. The data are shown in Table 31 and are plotted in Figures 30-33. In mixed solvents, it is possible to see bound and bulk ion signals from both solvents (132). However, only one Tl+ ion resonance was observed in our systems which suggests that the + exchange between the bound T1 ion and bulk T1+ ion is fast 139 n.mmmI 00H 0.00HI om.oo m.HmH nH.oo m.nnnI 00H o.n0m om.oo n.00a no.00 n.H0 I 00H H.00m :n.:0 n.nnm no.0n 0.0n no.00 o.nmn H:.No n.nnmI 00H 0.0nn mn.nn H.00H na.so N.mon 0:.sn :.mm om.mn 0.H0n Hm.m0 o.o:m on.:0 H.non 00.nn H.::H Ho.nn N.HH: No.3n o.wnn ss.mm 2.0on no.00 n.00m 0:.n0 n.0H: N:.nn o.nsn nn.sn n.50n 02.nn :.mnn ma.mw n.00: nn.00 :.n0n an.on H.5on n:.m: o.nmn mm.0n n.00: Hm.0o n.m0n 20.0n n.50n 05.0n n.0on n:.nn n.00: no.0n H.Hon 00.na n.50n sm.m~ H.30n mo.mn 0.00: ms.:m m.oon oo.m o.m0n no.nH o.mon mH.nH n.Hnn :n.ma 0.0mn 00.0 :.n0n 00.0 m.onn 00.0 0.00n 00.0 Aemmvo mme mo Asmmvm Z¢ mo Aemmvo om mo “suave Ez mo R mHOE we wHOE We. wHOE R mHOE Anoaoae s noo.ov 0mzp\zz Asoaoae 2 n00.00 omsp\om Asoaoas s Ho.ov AooHoHe z n00.00 0mzp\zs omsp\mme .mesoeaom oosHs sH soaoae no nsHHom HmoHsono momIssHHHmos .Hn manna 140 n.nnm I 0.0 2.:o 5.2 m.m 0.0 n.o n.n m.5 n.m m.H: 2.5 m.mn 2.0 m.:o 5.02 s.mmH ooH o.o: m.nH n.mm o.oH n.ns: ooH 5.nHm Hm.0w 5.mo o.mm n.5oH 0.mm n.02: 20.n0 n.30m m0.m5 n.20 0.nm m.mHH n.Hn m.o:: No.05 n.20m 0m.n0 0.022 H.nn n.0mH o.o: «.23: so.m0 n.02n 5o.mn m.nHH H.H: H.0nH 0.0m 0.nn: wo.m: n.0mn om.5s 5.0NH n.mo o.HnH 3.20 0.om2 00.5n 5.5nn 20.nn 5.5NH 5.50 H.mnH ~.n5 0.022 5n.mm n.02n 5m.mm n.0ma n.3m n.mna n.05 o.don om.2a m.~nn 25.n2 m.onH H.00 m.nnH m.mn n.05n mn.: H.00n om.n 5.nnH 0.002 5.nnH 0.002 :.mon 00.0 o.mon 00.0 Aemmvo msm Ho “Emmvo REG Mo Asmnvo ¢m2m mo “agave msn Mo & oHoE & macs & macs R oHoS 2302022 2 20.00 0m2p\m20 2202029 2 20.00 om2p\ DMSO > H20 > PY > DMF > THF > PC > AN > NM. By comparing these results with dielectric constants or donor numbers of solvent (Table 33). a good correlation was observed between the iso-solvation point and the donor number of the solvent in various binary solvent systems as shown in Figure 35. The above results clearly indicate that the mole % of DMSO at the iso-solvation point increases with increas- ing donor number of the second solvent. The data show that the donicity of a solvent is more important than its 150 Table 32. Preferential Solvation Data of Several Binery Solvent Systems. Binary Solvent Systems Isosolvation Point NM/DMSO 0.005 MFbDMSO AN/DMSO 0.014 MF DMSO PC/DMSO 0.020 MF DMSO THF/DMSO 0.028 MF DMSO DMF/DMSO 0.168 MF DMSO PY/DMSOa 0.25 MF DMSO H20/DMSO 0.27 MF DMSO HMPA/DMSO 0.790 MF DMSO AN/DMSO 0.17 MF DMSO HZO/DMF 0.02 MF DMF b aReference (109). MP: mole fraction Table 33. The Gutmann Donor Number and Dielectric Constant of Several Solvents. Solvent Parameter NM AN PC THF DMF DMSO H20 PY HMPA Gutmann Donor Number 2.7 14.1 15.1 20.0 26.6 29.8 33.0 33.1 38.2 Dielectric Constant 35.9 38.0 70 7.6 36.1 45.0 78.5 12.3 30.0 151 (~er I I I l PY/DMSO 20 /DMS 0 30.— o DMF/DMSO $4 (1) ,0 8 z 20- THF/DMSO 1 g 0 8 0 PC/DMSO AN/DMSO 10. .1 NM/DMSO . l J 11 f 1 0 0.2 0.4 0.6 0.8 1.0 Mole Fraction of DMSO Figure 35. The plot of Gutmann donor number vs. iso-Solvation point in several DMSO binary mixtures with other solvents. 152 dielectric constant scale in determining its relative sol- vating ability. Convington §t_a1. (134-136) have recently develOped a quantitative model for competitive solvation. In their papers, they present an equation of preferential solvation which allows the calculation of geometric equilibrium con— stants and the changes in free energy as the solvation shell of an ion is progressively changed from one solvent to an other. In Figures 30-33, most of the thallium-205 chemical shift curves go through a minimum at about Xp= 0.8, which indicates that there is not only simple ion-solvent inter- actions occuring in our systems, but also other factors such as ion pair formation. These figures can not be fitted to the Convington equation. 3. Complexation of the Tl+ Ion by DA18C6 or DT18C6 in Mixed Solvents The complexation of the Tl+ ion by DA18C6 and DT18C6 in various organic solvents has been studied, and the results are shown in Table 20. In these solvents, only a few values of the formation constants between 0 and 105 can be calcu- lated precisely as discussed in Chapter III. It is interest- ing to see how well the solvation of the Tl+ ion complexes in mixed solvents can be explained in terms of the complexed Tl+ ion behaviour in the pure solvent. Complexation of the + . T1 ion by DA18C6 or DT18C6 were studied in DMF/H20 orDMF/AN 153 binary mixed solvents, respectively. Thallium-205 chemical shifts were determined as a function of the DA1806/Tl+ or DT1806/Tl+ mole ratio. The results are listed in Tables 34 and 35. In all cases, only one resonance of the metal ion was observed, suggesting that the exchange between two sites (free and complexed T1+ ion) is fast compared with the NMR time scale. Graphical representations of the results are shown in Figures 36 and 37. The results clearly indicated that the nature of the medium plays an important role in the complexation process. For example, as the mole fraction of DMF in DMF/H20 (Figure 36) is increased, the plot shows pro— nounced curvature, which is good evidence for the formation of a stronger (DA18C6-T1)+ complex. When the DA18C6/Tl+ mole ratio is varied between 0 and 1, the thallium-205 line- width broadens as the mole % of DMF in DMF/H20 is increased probably because the exchange between two sites (free and complexed Tl+ ion) is slower in DMF than in H20. The values of the formation constants and the limiting chemical shifts for (DA1806-Tl)+ and (DT1806-Tl)+ complexes in various compositions of mixed solvents are calculated by fitting the variation of the thallium-205 chemical shift with the ligand/T1+ mole ratio. The results are summurized in Table 36. The data once again show that the values of the. stability constants (Kf) of (DA1806-Tl)+ and (DT18C6-Tl)+ increase as the mole fractions of DMF and AN are increased. The results obtained for these systems appear reasonable 154 «0 0.205 n0.0 22 5.205 52.0 00 5.n05 n2.0 o0 n.055 20.2 02 0.005 00.2 N0 0.005 20.n 50 0.055 02.2 00 5.:05 52.n 05 0.505 00.m 50 5.005 22.n 00 2.005 20.0 00 0.025 02.0 00 2.005 02.0 00 2.m05 00.0 00 n.025 00.0 502 0.005 05.2 05 0.025 00.0 20 0.025 00.2 200 0.005 on.2 05 2.n25 20.2 202 0.0n5 02.2 250 n.n00 20.0 022 0.205 02.2 200 0.000 00.2 0022 0.252 00.0 0n0 0.020 20.0 000 5.000 00.0 wn52 0.00n 02.0 I I 0n.o I I 0n.o 2052 o.n5m 20.0 I I 02.0 I I 00.0 52 5.0n2 00.0 20 0.002 o 02 n.2n2 00.0 222022 220000 +22\2 2smve< 220000 +22\2 Asmvaq 220000 +22\2 002 500\020 002 002 202\220 000 020 00:0 omm\02o s2 22 20.0020202e\000220 000 2220 00 22m 0 20 pm mpsc>2om 00222 22022020Io22m2 0202 .20 02909 155 000 0.000 20.0 022 0.005 05.0 05 0.005 2n.0 000 0.220 00.2 0n0 0.200 50.2 50 0.025 22.2 000 0.252 0n.n n02 0.200 2n.2 002 0.0n5 22.n 020 5.nn2 50.0 5nn n.000 00.n 002 0.025 00.0 000 2.502 02.0 500 0.220 02.n 2n0 0.500 00.0 020 5.05n 00.0 00n 0.020 00.0 000 0.020 00.2 000 2.50n n0.2 000 n.n00 0n.0 000 n.000 00.2 050 2.02n 20.2 222 n.520 20.2 000 0.2n0 00.0 050 0.200 00.0 000 0.002 20.2 000 0.0n2 25.0 2n0 0.002 00.0 0n0 0.50n 20.0 000 0.20n 22.0 502 0.002 0n.o 0n0 0.5n0 0n.o n00 0.000 n0.0 20 0.02 00.0 22 5.00 00.0 20 0.022 00.0 Asmvad 220000 +22\2 222094 220000 +22\2 Asmvaq 220000 +22\2 002 250\220 002 002 255\020 0n0 002 050\020 0nn .0mscfipzoo .20 02002 Nm OOOOH "3m um ooom "Ema 156 0 2n n.052 n2.0 2n n.002 20.5 5n 0.022 20.0 n 0.002 02.2 2n 0.002 2n.2 0n 0.022 00.0 20 5.002 50.0 2n 0.202 5n.n 50 0.022 00.2 2n 0.502 00.0 2n 5.022 02.0 0n 5.222 0n.n 2n 5.n02 55.2 00 0.022 00.2 00 2.n22 00.0 2n 2.002 00.2 2n 2.222 n0.2 0n 0.222 20.0 2n 2.522 20.2 2n 0.022 22.2 50 0.022 00.2 2n 0.022 00.2 2n 0.022 20.0 2n 0.0n2 00.2 20 2.n22 25.0 00 0.0n2 20.0 0n 0.0n2 00.0 2n 0.022 20.0 00 0.0n2 0n.o 2n 2.5n2 00.0 2n 0.5n2 00.0 00 0.0n2 00.0 nn 0.0n2 0n.o 2n 0.2n2 00.0 00 0.0n2 00.0 nn 5.nn2 00.0 2220>< 220000 +22\2 202004 220000 +20\2 2220>o_ 220000 +22} 22 20n\e20 220 22 02m\220 0050 220 00000 mocommpm 022 C2 A: 20.0002 .0 20 20 0200>2o0 00222 220\z< 22 000202 20 02020 0o2 0200 22220 20022020Io2202 0202 .mm mdnme 157 50 0.00n 00.0 nn 0.050 00.0 00 0.200 00.5 50 0.20n 00.n nn 2.000 00.n 00 0.000 00.0 50 0.02n 00.0 nn 0.220 00.0 20 5.002 00.n on 0.0on 50.0 nn 5.0n0 02.0 20 5.n02 00.0 on 0.500 00.2 0n 0.020 05.2 20 2.252 00.0 on 0.250 0n.2 nn 0.200 02.2 20 2.002 00.2 02 0.020 no.2 nn 2.002 00.2 20 2.202 20.2 02 0.020 20.0 nn 2.052 00.0 00 0.022 00.0 20 5.202 50.0 0n 5.n02 20.0 20 0.022 n5.0 20 0.022 5n.o 20 0.5n2 0n.0 20 0.0n2 02.0 02 0.0n2 50.0 20 2.002 02.0 20 2.002 00.0 n0 0.20 00.0 20 0.502 00.0 20 0.002 00.0 Aumv>4 259200 +HE\2 Ammv>< 282200 +HE\2 Aszv>< 289200 +HB\A 22 000\m20 022 22. 05502222 0n0 22 200\220 0 22 .moSEHPsoo .mm wands 158 O ‘ I 1 1 l i I 0 1 3%DM P/8 7%H 20 . o 23%DMF/77%H 20 _ e 3 3%DMF/67%H 20 ZOO A 48%DMF/5 2%H 20 J ' 8 5%DMF/1 5%H 20 A E 0' 1 O. 400 r- 00 600 t “ __ ‘ - 4 ‘- ' a r- 800 1 I | l '— O 2.0 “CO 6.0 [DAI806]/ [TU] Figure 36. Thallium-205 chemical shifts vs. DA18C6/T1010LL(0.01M) mole ratio in DMF/14120 systems. 159 I I T l j —300 ' " o 01% DMF/ 59% AN . o 23% DMF/ 77% AN ”200 o 11% DMF/ 89% AN ‘ 0 Pure AN —100 2 _. A O P - E 0. CL k 2 V 100,‘ w ‘ O 5‘ 200.. “ " 2 _o.__. 300 - , J .. $— 400 I- -‘ fl 1 1 4 1 J J 0 1.0 2.0 3.0 4.0 5.0 6.0 [0TI806]/ [TU] .Figure 37. Chemical shifts of T1-205 vs. mole ratio of (DT18C6)/(Tl ) in DMF/AN mixed solvents. 160 100 I I I I I 0 Pure DMF ° 79 % DMF/ 21 % AN A 61 % DMF/ 39 % AN llOr‘ 120.. [/3 130- ° - 140- 8(Pm) 150‘ 160- 170" 180 J I J 1 O 1.0 2.0 3.0 4.0 5.0 [DTIBCSJ/ [TU] Figure 37. Continued. MIL. AD _ p CU Ilw. Ac); 21F 161 Table 36. Log of Formation Constants and Limiting Chemical Shifts for (DA18C6-Tl) and (DT18C6°T1) Complexes in Mixed Solvents. Limitin Chemical Solvent Log Kf Shift (5pm) 1 (DA1806-Tl)+ pure DMF 3.55 i 0.03 766.5 i 0.1 85% DMF/15% H20 3.59 i 0.03 764.8 i 0.4 48% DMF/52% H20 3.09 t 0.03 792.6 i 1.1 33% DMF/67% H20 2.65 i 0.02 790.0 i 2.3 23% DMF/77%IH20 2.26 t 0.02 776.8 f 3.7 13% DMF/87% H20 1.70 t 0.02 783.6 f 13.5 pure H20 0.96 i 0.01 824.7 f 13.4 (DT1806-Tl)+ pure AN 4.16 i 0.06 388.7 f 0.3 89% AN/ll% DMF 2.70 i 0.01 341.4 i 0.5 77% AN/23% DMF 2.00 t 0.02 309.2 i 3.2 59% AN/4l% DMF 1.50 t 0.02 265.5 i 2.7 39% AN/6l% DMF 1.46 i 0.07 205.3 1 7.0 21% AN/79% DMF 1.20 i 0.04 203.6 i 4.2 pure DMF 1.19 i 0.06 168.2 f 3.0 162 because solvents with large donor number, such as DMF (D.N.= 26.6) in DMF/AN and H20 (D.N.= 33) in HZO/DMF, have rel- atively larger solvating ability for the Tl+ ion, hence a smaller complex formation constant is obtained. The varia— tion of the stability constants of (DT1806-Tl)+ or (DA1806.T1)+ with composition of mixed solvents is plotted in Figure 38. It is interesting to note that, in all cases, the limiting chemical shifts for the complexed Tl+ ion are de- pendent on the solvent composition suggesting that the com— plexed T1+ ion is only partially insulated from the solvent molecules. 163 5 O T I I I I _l ' 1 ' 'AN 4.01 + IDM‘? (DA1806.T1) 3.0- CH .521 00 O I-‘l 2.0- DMP‘$/, (DT1806.T1)+ #120 ‘ 0.0 n l l I l I J l J 20 40 60 80 100 Composition of Mixed Solvents ( Mole % ) Figure 38. Log of stability constants of (DT18C6°T1)+ and (DT18C6-Tl) complexes vs. solvent composition in DMF/AN and HZO/DMF mixed solvents. CHAPTER VI MISCELLANEOUS 164 1. Complexes of 18-crown-6 and Its Analogs Studied by Proton and Carbon-13 NMR Although x-ray studies give conformations of the metal complexes of 18-crown-6 and its analogs (35.59.67.77) in the solid state, it is apparent that the structures may be dis- torted by such factors as intermolecular hydrogen bonding and crystal packing relative to the "free" molecule (139,140). Furthermore, since most chemical reactions are carried out in solution, it is important to establish conformations in this state. Nuclear magnetic resonance studies have been used to elucidate the effects of the factors such as ring substituents, donor atoms and central metal size on crown ring conformation. We have chosen the NMR method because of its unique ability to give the desired information provided that the complexes are suitably designed. Complexation of the thallium(I) ion by 18C6 and its analogs in various solvents has'been presented in Chapter III of this thesis. The results show that the conformation of DT18C6 changes during complexation. Proton and carbon-l3 NMR were used to identify this conformational change. In this thesis, all chemical shifts of the 13C resonance are referenced to the methyl group of Me0D. As shown in Figure 17, the complex, (18C6-Tl)+ formed in DMF results in a upfield shift for the carbon-l3 resonance. Figure 39 shows 130 NMR spectra of 1806 (0.02 m) in AN-d3 with Me0D as an external reference. Since all carbon nuclei 165 166 .002020002 00 0002 2223 m @172 C2. 22 00.00 0002 20 0020000 222 n2Iso0000 .0n 020022 0700 20.. 012.0. 167 in 1806 are magnetically equivalent, only one 130 resonance at 21.76 ppm appears in this spectrum and it shifts upfield (Table 37) as the metal ion/18C6 mole ratio is increased (1.3. the complex is formed). The ligand DB18C6 has three sets of equivalent carbon nuclei (C(1), C(2) and C(3) in Figure 40). The two benzo rings on DB18C6 withdraw electrons from the crown ring, therefore the electron density on the carbon atoms decrease in the order C(l) > C(2) > C(3). Con- sequently, the chemical shifts of C(l), C(2) and C(3) on DB18C6 in DMF are 19.66 ppm, 20.96 ppm and 100.01 ppm respec- tively. Similarly in DMSO the chemical shifts of C(l), C(2) and C(3) are 19.43 ppm, 20.75 ppm and 99.78 ppm respectively. Table 38 shows that in both solvents, all three 13C resonance frequencies shift upfield as Tl+/DB18C6 mole ratio is in- creased, and the chemical shift change is in the order C(3) > C(l) > 0(2). Three sets of carbon nuclei (C(l), C(2) and C(3) in Figure 41) are found in DA1806. In DA18C6, the electron withdrawing ability of the oxygen atom is higher than that of the nitrogen atom, therefore, the electron density on carbon decreases in the order C(l) > C(2) > C(3). The result is that the chemical shifts of C(l), C(2) and C(3) on DA18C6 in AN are 0.54 ppm, 21.38 ppm and 21.66 ppm respectively. Table 39 shows that all of these three l3C resonance fre- quencies shift upfield as the cation/DA18C6 mole ratio is increased, and the chemical shift change is in the order C(2) > C(3) > 0(1). 168 20.20 20.2 202020 25.20 00.2 n0202 00.20 00.2 0202 05.20 0 2 00.0 220000 0002\+2 0002 2200 .QOMPsaom mUIz< :2 202200 2223 2022200 0002 200 020m 02202 0202IP0220 20028020 021:09200 .50 02909 169 .mothm%mp mm Ulz< m 0-20 002; 020 :2 22 20.00 000200 mo 0000000 022 m2-conumo .0: 003020 2:0 Nlo 0:0 20.022 00.002 2:0 02.522 20: m 0|z< N2.m:2 mn0 No.2o2 170 i! -01 J I'll-’1)- 00.00 00.00 00.02 02.2 00.00 00.00 00.02 00.2 00.00 00.00 00.02 00.0 00.00 00.00 02.02 00.0 00.00 00.00 00.02 00.0 00.00 20.00 00.02 00.0 20.00 00.00 00.02 00.0 00.00 00.00 00.02 0020 0 20.002 00.00 00.02 020 0 2 00.0 8990 Emmv Emmv 0002mm Asmmv AEQQV AEQQV 0002mm M000 0 M000 0 M200 0 0000200 1H2HII 2000 0 2000 2200 0 000>200 .IH2HI: 000200 02 002020 0023 0020000 000200 000 0000 02000 0202. 20020000 02-000000 .omEQ USN mED .wm m2nme 171. .000000000 00 00-00 002; 20 02 22 00.00 000200 00 0000000 022 02-000000 .20 000020 pééifié Egg} 3- 02.20 20.20 0-0 0-0 0N . om Huo ... 32) o no 0 0:0,. m 0 CU : 05C III, . » .U .. l. 1H: MW. £02000 c023 x02geoo 0002<0 000 0000 00000 0202 00.: HMOHfimwu MHICOthU .mm mHQNR 172 00.20 00.00 00.0 00.2 0 00.0 0000 20.00 00.02 00.0 00.2 00.00 02.00 00.0 00.0 0 00.0 002020 00.20 00.20 00.0 0 2 00.0 00.20 00.20 00.0 0 2 00.0 Mwwmv Mwwmv0 Mfiwmv 000200\00 000200 _ 0200 .mQthmMmm mm 0002 £003 20 C2 002000 0023 0020000 000200 000 0000 02000 0200-00200 20020000 02-000000 .00 02000 W CL C; 173 Three sets of carbon nuclei (C(l), C(2) and C(3) in Figure #2) are also found in DT18C6. In DT1806, the electron withdrawing ability of the oxygen atom is higher than that of the sulfur atom, therefore the electron density of the carbon atom decreases in the order C(l) > C(2) > C(3). and the chemical shifts of C(l), C(2) and C(3) on DT1806 (0.0# M) in acetonitrile are -l7.12 ppm, 21.72 ppm and 23.26 ppm respectively. Table 40 indicates that 13C resonance shifts upfield for C(2) and C(3) but shifts downfield for C(l) as the cation/DT1806 mole ratio is increased, and the chemical shift change is in the order C(3) > C(l) > C(2). In the identification of the 130 resonance for three kinds of carbon as described above, we assume that carbon nuclei are diamagnetic nuclei. Since the 130 chemical shift differences between C(1) and C(2) on DB1806, C(2) and C(3) on DT18C6 or DA18C6 are very small, the peak assignment is unsure. Isotopic labeling studies are required for exact site assignment. Comparing the results described above, it is interesting to note that the C-13 resonance of all carbons on the crown ring of (1806-M+), (DB18C6-Tl+) and (DA1806-M+) complexes are upfield (shielding) compared with the respective free ligands. On the other hand, in the (DT1806-M+) complex, carbons 2 and 3 shift upfield but carbon 1 shifts downfield as compared with the free DT1806. The crystal structure of the DT18C6°PdCl2 complex (77) shows that only outwardly .000000000 00 0002 0023 20 02 02 00.00 000200 00 0000000 000 02-000000 .00 000020 J0 0 0 . NHéHI 17L; 00.00- 00- 20 = 00.20 00.00 N10 m-o 00.00 75.. z< 3.) O O 00 u 0 O 0plixm/(L 175 oo.mm mu.am om.na- mm.o om.mm mm.am omaman 02.0 ommx mm.mm mm.am :m.na- o o< 2 20.0 Hm.HN om.am om.ma- mo.H :nmmm mo.mm mm.am um.oa- Ho.a mm.mm mo.am om.ma- om.o mmmm :m.ma No.0m mm.mH- wo.H mm.am mH.HN m:.oa- om.o :oaoae mm.mm mu.Hm mo.na- o 2 No.0 :m.ma mo.am m:.:a- mo.H mo.am H:.Hm mm.ma- m:.o mozm< mm.mm mm.am ma.ma- o z< 2 30.0 Amvo Amvo Aavo oomaeo\wz pcm>aom mowaeo pfimm .moCmanmm mm new: spa; o¢ no z< CH mflowpmo m50fl9w> gpfia xmamsoo evades pom mama oapmm maoz-pmflcm HmoHEono mangoppmo .0: mapme 176 turned sulfur atoms participate in coordination with the Pd2+ ion. The complexing strength of 1806 and its analogs with the Tl+ ion, shown in Table 21, generally decrease in the order DA18C6 > 1806 > cis-syn-cis-DClBCé > DB18C6. These results suggest that only two sulfur atoms take part in the coordination with the Tl+ ion. The 130 resonance data dis- cussed above seem to suggest that, in solution, (DT1806-Tl)+ has the following structure (C). While, (DT18C6-Ag+) has the other structure (D), since stability constants of 1806 and its analog with the Ag+ ion are in the order DA1806 > DT1806 > 1806 > DB1806 (10, 59, 63. 76). '1- TI 3/ \S S\ / 3 l I, \\ I? \ 22 (C) 13 (In /7 \ o o | l ’1 \\ O O 3 It is obvious that there is a quite strong angle strain on carbon 1 site which may induce a downfield chemical shift. Conformational changes on complexation, were also studied by proton resonance spectra. Acetonitrile-d3 was selectes as the solvent in all studied systems and all chemical shifts reso- nances are referenced to the hydrogen nuclei in acetonitrile. 177 In 1806 and its complexes, all protons are magnetically equivalent, therefore, only a single resonance is obtained. It is intesting to note that this resonance shifts downfield (Table 41) as the metal ion/1806 mole ratio is increased. Three sets of 1H nuclei are found in DT1806 as shown in Figure 43. Figures 43 and #4 show the proton NMR spectra of DT18C6 and its complex with the K+ ion which show that the protons on the carbons (0(1) and C(2)) form two triplets with a 1:2:1 intensity ratio since this system is made up of two sets of magnetically equivalent nuclei (an.A2X2 system) (141). While the protons on the carbons C(3) between two oxygen atoms are made up of one set of magnetically equiva- lent nuclei (an Xn system), therefore their resonance appears as a singlet with chemical shift 1.611 ppm (65,66). The calculated NMR parameters are shown in Table 42. Proton NMR spectra (Figure 51) of the two complexes, (DT1806-T1)+ and (DT1806-Ag)+, show some multiplets existing in two triplets. On the Bruker WM-250, the DISNMR program is more powerful than the general proton program, on which gaussian multiplication (GM) and zero filling techniques can be used to improve the resolution of the spectra. The technique uses 8K or 16K memory for acquisition and gaussian mutiplication, then with the éfiK memory for fourier trans- forms (FT). After treating the NMR spectra (Figure 45) with this technique, a better resolution spectrum as shown in Figure #6 was obtained. 178 moo.a Ho.H soaoae :um.a mo.a mozm< ome.a mm.a mama mom.H o 2 No.0 Asmgvs mowa\+2 coma pamm .m U|z< Ca mCOflpmo mSOHum> Spas meQEoo coma ho% Mpmo oapmm maozrpmflcm aonEmno Gopohm .H: manna .ms-z< as A: mo.ov somaea mo mopomam mzz cocoom .m: mbSMam 179 mmwd cacé N .H . s a sexy 3.). O O ©.mfl0 0U :.m_/\m/\_ N.H Haw...” QQQm—O 180 .mclz< Cw HO.H n Wwaemo%o whpoomm mzz CoPOMA .3: mpsmfim mm: clz¢ .L mmm.o N a om©.H . mmoé mo.ms 181 mpszmCoo mcHHQSoo .Emm CH mawnpflcopmom Scam camfiwssov mum mpmflnm HmoMSmnon. . .Eopmmm NNN< CH x29mazefim one .22 mgsm2a 187 may indicate that a very weak complex is formed between the K+ ion and DT1806, therefore, the conformation of DT18C6 in the complex is still flexible, and the two hydrogen atoms on the same carbon (carbon 1 or 2) remain magnetically 1H and 130 chemical shift equivalent nuclei. The small changes for the (DT1806-K+) complex as compared with the free ligand (Tables 39 and 42) also seems to incidate that a very weak complex is formed between K+ and DT18C6. Table 42 indicates that all lH resonances shift down- field as the complex is formed and the chemical shift change is in the order: 1H on C(l) > 1H on C(3) > 1H on C(2). The results indicate that J13=J24 and J14=J in both the (DT- 23 1806-Tl)+ and (DT1806-Ag)+ complexes which demonstrate that the time-averaged dihedral angle 9 between protons on C(1) and C(2) are 913:924 and elu=923. The result, J12=J34’ shows that the H-C-H angles of geminal protons on C(1) and C(2) are also the same (612=934). All of these results clearly indicate that the conformation A is preferred over the conformation B (91429 ). 23 (B) 188 These coupling constants were also used to obtain the dihedral and H-C-H angles of geminal protons by the well known relationship first described by Karplus (143-145). 29 - Bcose + C, are Since the coupling constants, J= Acos constants affected by the nature of the substituent attached to the vicinal carbon atoms, the direct reading of the angle 6 from the magnitude of the J value is not real. In the case of the (DT1806-Ag)+ and (DT1806-Tl)+ complexes, the predicted angles are 914:923=34°, 912=eBQ=116°, and 913: 624:150O which results in 613=912 + 923=15O°. However, the total (912 + 923 + 934 + 94“) is equal to 3000 instead of 360°. The proton NMR spectra of DA1806 are shown in Figure 49 in which the AA'XX' system is indicated for the two sets of protons on the carbon atom between the oxygen and the ni- trogen. The same type of proton NMR spectra was also obtained for the (DA1806-T1+) and (DA1806oK+) complexes. These proton signals were simulated by the PANIC program and the calculated NMR parameters are shown in Table 43. 1H resonances shift down- It is interesting to note that all field as the complex is formed. The chemical shift change is in the order: 1H on C(l) > 1H on C(3) > 1H on C(2). Table 43 shows that the coupling constants of DA18C6 and its complex at the same site are nearly the same value. These results demonstrate that there is no conformational change as the complex is formed. The results show the angles are 189 2 m .so2pdo22a2p2ss amflmmswm £923 wcfipmoap ampwm A: No.ov oom2¢o mo nupooam msz sopoum o U|z< % . 2.1 oom2 10"ll sec) than the rate of redistribution of energy in the internal degrees of freedom, both electronic and vibrational, so that a "quasi- equilibrium" among these energy states is established before ion decomposition takes place (158). Quantitative description of the fragmentation of large molecules is based on quasi-equilibrium theory (159.160). According to this theory, the fragmentation processes of the molecular ion can be considered separately from the act producing the ionization and internal excitation energy dis— tribution. Further, the fragmentation processes can be described as a series of competing, consecutive unimolecular reactions. The dissociation mechanism in a polyatomic species can be described as a motion along a multidimensional 200 *- (a)AB+e—>ABt+2e (b)AB+e—>AB:r +2e Energy Energy A—B separation A-B separation (c)AB+e—>AB3§+-A++B+2e(d)AB+e—>A++B+2e Energy Energy A-B separation A—B separation Figure 51. Electron impact ionization of the molecule AB an excited state is indicated by * . 201 reaction coordinate separable from all other internal coor- dinates through an activated complex configuration. It often consists of a sequence of steps and is therefore controlled by several bottlenecks. The complicated and multistep nature of the dissociation reaction results in a natural tendency toward energy randomization (161). The probability function, P(E), and the rate constant, K(E), of various possible decom- positions of an ion depend on its structure and internal energy, but not on the method used in initial ionization and the structure of precursor. The rate constant for a decom- position reaction is described by the Rice-Ramsperger—Kassel- Marcus (RRKM) theory (162): K(E) = Where h is Planck's constant,cxis a symmetry factor, G*(E-EO) is the total number of quantum states of the transition state between zero and (E-EO), and N(E) is the density of states of the reacting ion. The relationship of P(E) and K(E) with ion internal energy for unimolecular ion decomposition has been discussed in detail by Bente and co-workers (163,164). In the case of larger molecules impacted by electrons, significant numbers of them are initially in higher vibra- tional level of their ground electronic state; they become an activated complexes after collision with energetic 202 electrons. The dissociation products are formed after energy randomization of the activated complex. Depending on the energy of the incident electron, various dissociation pro- ducts can be produced in the ways shown in Figure 52. Positive-ion mass spectrometry can be used for studying ionic products from pathways c,d,e,f,g,h and l. B. The Mass Spectra of Crown Ethers Mass spectrometry has been widely used for the elucida- tion of the structures of crown ethers with one or more aromatic or heteroaromatic substituents. However, in most cases, only the molecule compositions are described. To date only a few detailed fragmentation patterns have been reported. The fragmentation patterns of several cyclic ethers such as p-dioxane and tetrahydrofuran, under various electron impact energy were examined early by Collin et_al.(147,165). The ionization and appearance potentials of numerous ions have been determined and then used to interpret the dissocia- tion mechanism. Linear intermediates were used to explain the mass spectra of such small cyclic ethers, ;.e. + + 0 - c-c—o-c-c-o - j —{:[ 1 +\ FRAGMENTS o [c-o-c-c—o-c] -/' 203 .moasooaoe mwmzm mam pom CoapfimomEoomc pommEH Convomam Mo mzmznpmm one COHPNEMOM MHNQ Cow COHPwPCmemmm% CoaPMPHoxw\d0Hpmp:msmmmM Soapmpwoxm COHPMPCoEmmMM\dOfipmNw:oa\pcm8omzmQMMou CQfiPMPCmsmmmy\fiowpmNfl:oa CowpmNHCOH mansov CoaPMpfloxm\d0HPMpsmemmpm\d0flpmNflCOH COHPMPHoxm\d0HpmNHCOw cowpmNHcOH mMSPQmO mocmsommp COHpmpCmEmmpM\mMSPQmO Coppomam A3 3: A: 2; C: Amv CV A3 :5 it it 23 .mm 8&2. m + Imm + mm.ll|l m + mm + Hm Ill! M>£ + m +Nm + Hm IIIJ. M>£ + w + E llll. mm + 3m + +mm.llll mm+ mm + +Hm ....Il +N2 AI“! mm + *A+Ev .IIIJ .53 + Na + Hm Ill. M>£ + mm + +5 Illl. mm + +2 llll -2 ll. mm + Hm llll AmemEoo umpm>apomv * E + m a E + w 204 Initial C—O cleavage was preferred over C—C cleavage in such small cyclic ethers. In the case of tetrahydrofuran m/z 44 was the base peak and the configuration of W was sug— gested for this ion. In 1970, the mass spectra of catechol polymethylene di- ether homologs of the type 0 )CH2)n n= l-5 0 were reported by Biemann et_al. (148). Deuterium labeling experiments have been used to identify the fragmentation mechanism. The results show these compounds are structurally similar to crown ethers, but behave much differently on fragmentation. In 1974, Liotta gt al. (149,166)reported the synthetic pathways for 1204, 15C5 and 1806. They also reported 6 ions mass spectra but did not discussed the spectra in detail. In 1975, the mass spectra of a series of benzo-crown ethers were correlated and compared with those of open-chain analogs. Mass spectra of some deuterated analogs were used to formulate the fragmentation pathways. The loss of C2H4O units in these series of crown ethers was discussed (150). In 1977, Oliveira gt_a;,(151) reported the mass spectra of dibenzo-lB-crown-é (DB1806) and three of its nitro derivatives. 205 Metastable ions were used to identify the fragmentation mechanism. The fragmentation patterns of DB18C6 suggested that ring contraction through loss of CzHuo occurs. Three derivatives dissociate by ring contraction as well as through losses of O. NO and N02 species. In the same year. the de- tailed mass spectra of several serial compounds of the type were reported by Gray and co-workers (152). High resolution measurements and metastable ion analysis were used to iden- tify the product ion structures and to postulate the fragmen- tation mechanisms. In all cases. m/e 45 with the proposed structure H4- 0 A was the base peak. The m/e 177.133.89.45 series was always 206 observed. The initial site of ionization on the aromatic group is presumed. In 1980. Whitney and Jaeger (153) reported the mass spectra of pyridyl crown ethers. The spectra of some deute- rium labeled analogs of pyridyl crown ethers coupled with high resolution measurements were used to formulate the fragmentation mechanisms. Fragmentation by loss of CZH4O units was observed. These were complex spectra in which the total ion current was not carried by a small number of ions. 3. Experimental A. Reagent Purification Linear polyethers. triethylene glycol dimethyl ether (Aldrich. 3-EGDME) and tetraethylene glycol dimethyl ether (Aldrich. 4-EGDME) were distilled under vaccum and middle fraction was taken. Macrocyclic polyethers lZ-crown-4 (Aldrich. 1204) and 15-crown-5 (Aldrich. 1505) were also purified by the procedure described above. The ligand 18- crown-o (1806) was purified by the method described in Section II-l of Part I. The ligand. Zl—crown-7 (Parish. 2107) was used as received. B. Sample Preparation The samples were prepared by dissolving 0.1 ml of 3-EGDME. 4-EGDME. 1204. l5C5. 2107 or 0.05 g of 1806 in 1 ml of meth- anol respectively. 207 C. Instrumentation The mass spectra of crown ethers and linear polyethers were obtained by using a Hewlett Packard 5985 gc/ms/ds spec- trometer. The HP 5985 GC/MS is a complete system including an HP—5840A GC. digitally temperature controlled dual chemical ionization/electron impact ion source. quadrupole mass filter. electron multiplier detector. differentially pumped vaccum system. ion gauge controller. ionization region pressure gauge. gas inlet probe. programmable direct insertion probe. inlet vaccum system. GC/MS jet separator interface direct transfer line. and a direct capillary interface also provided. The data system includes an HP ZlMXE series micropro- grammable 16-bit computer with 32K of memory; HP 7900 A dual disc drive. The usable mass range is from 10 to 1000 atomic mass unit. The ionization energy (EI) range is from 10 to 250 eV. The samples of crown ethers were introduced both via the CC (0.1 ul injections using a 25 meters OV-l capillary column) and the direct insertion probe. Samples of 3-EGDME and 4-EGDME were introduced via the GC with 0.1 ul injection using a 2 mm(ID) x 6 ft column packed with 5% SE-30 on 80/100 mesh Gas Chrom. Q. 70eV electron impact (EI) spectra of linear polyethers and crown ethers were taken. Mass spectra (70 eV EI) at different crown pressure have been determined. Elec- tron impact spectra of 18C6 at a series of electron energies were also taken. 208 4. Results and Discussion A. Mass Spectra of Unsubstituted Crown Ethers The mass spectra of 1204. 1505. 18C6 and 2107 are shown in Figure 53. The ion abundances and preferred molecular composition of principle fragment ions are listed in Table 45. It is interesting to note that the spectra are essen- tially identical. In all cases. m/z 45 is the base peak. The spectra are dominated by protonated small crown ethers such as m/z 177 (protonated 1204). m/z 133 (protonated 903). m/z 89 (protonated p-dioxane) and m/z 45 (protonated ethylene oxide). This series of 177. 133. 89. 45. corresponds to the successive loss of the CZH4O unit (44 u). After comparing our results and the mass spectra of similar crown compounds presented in previous works as described in our historical review, an interesting framework is deve10ped. According to this framework. the fragment pathways are proposed and the mass spectra of ligands I-IV can be interpreted. Comparison of the results shown in Table 45 and Figure 53 lead to the following observations: 1. The mass spectra of compounds I-IV are essentially identical with m/z 45 as base beak. 2. In all cases. the molecule ion was not found. 3. The highest mass ion of significance in compound III and IV is m/z 177. while in compound I and II 209 _”"-’b’> ‘ .aoam Aav coma on mama ADV :oma Amy he «became mama >m on was at In a: :— 0: a: ’b"P’b’L?’DF~PF>. Db’b rPDbr.’D”P”iFD’IP’IID’~”4D.’>P’.DD}.I.~D5"~P'4KPI~PEWE .mm maamaa _ -4- . an. no.)oxJo e 9c _ .. P’DDD-rP44-Db’b-’D’pr'Ib-D”’-DI’b-"’I.’t’-)0b’0b’b;pt’bb”rr-ybDPFx-D’: b} h 1‘ d "’ "D’pb”’.l’ll’_”>’-’t'.— “._)‘+ d _ i l _ m; ... .3 r’.DDD’r.’bbPID->DD0PPDFD-5tbi—r>0>’-?’D’->"IPDD’ ‘1 ........ET ‘ .”*\'—”? _ . m an. o a=.(Lw(» d fiffijTTv bD’PF_?PD’bLIDDPF’DDb?’Dbp”bb-’?"pbilDprb’bbIDhb’b’I-FFD’PLLLprbb4’F4 o 1. ‘ p>>yrptbFn ”’bbb’b’ Ptb’bt’P .__.. 5;? ...: n. DJ .3 oo/|\ n: ea ‘ no 11 210 Table 45. Principal Fragment Ions in the 70 eV Mass Spectra of Crown Ethers. Fra ent Ion 12C4a 1505b 18C6c 2107d Elemental (m 2 value) Composition 41 4 5 5 5 CZHO 42 11 10 10 10 CZHZO 43 53 50 52 49 C2H3O 44 32 31 28 3O CZH4O 45 100 100 100 100 CZH5O 55 1 1 1 CjHBO 56 2 2 2 2 C3H4O 57 12 11 11 10 C3H50 58 18 17 21 19 02H202'03H60 59 12 15 20 18 C2H302.C3H7O 6O 1 1 2 l C2H4O2 61 3 l 1 l CZHSOZ 69 1 l 1 1 C¢H5O 70 6 6 6 6 C4H6O 71 7 8 ll 10 C¢H7O 72 16 l3 17 15 03H402.C¢H80 73 29 32 41 35 C3H502.C¢H90 74 4 2 2 2 C3H602 75 4 4 4 03H702 85 1 1 l C¢H502 86 5 5 7 6 C4H602 Table 45. Continued. 211 Fragment Ion 1204a l5C5b 18C6c 21C?d Elemental (m/z value) Composition 87 22 26 33 29 C¢H702 88 16 20 18 16 C4H802 89 41 50 73 70 0.31902 90 2 2 3 3 C4H1002 99 1 l l C5H702 100 1 1 l 05H802.C¢H403 101 6 7 10 10 C¢H503.05H902 102 2 2 2 2 C¢H603.05H1002 103 2 2 3 3 C¢H703.03H1102 104 2 1 C4H803 105 1 1 l 1 C4H9O3 115 l 2 2 C6H1102 117 1 3 4 4 C6H1302 131 2 2 2 06H1103 133 6 14 15 15 C6H1303 134 1 1 1. C6H14O3 177 l 3 3 08H1704 $1204. 12-crown-4, M.W = 176 1505. l5-cr0wn-5. M.W = 220 31806. 18-crown-6. M.W.= 264 2107. 21-crown-7. M.W.= 308 212 is m/z 133. 4. The predominant fragments of I-IV are small proto— nated ethers at m/z 177.133.89.45 which are separated in mass by the basic crown ether unit. C2H40. From the similarities of the spectra. a preferred sec- ondary structures of several intermediates can be assumed in the fragmentation pathway for crown ethers. In general. it makes little sense to assume specific secondary structure for molecules fragmentation in gas phase. Crown ethers may pro- vide us with an exception. since they are highly function- alized molecules. As the size of molecules. which are studied in mass spectrometry. increases generally the "exactness" of frag- mentation pathways described are frequently decreased. Fragmentation mechanisms are often presented which accurately describe the results. but involve interaction of parts of the molecule which are not obvious (g;g; interaction of groups on opposite sides of a large ring). This is. of course. due to the fact that molecules drawn in two dimensions are actual- ly three dimensional. Analysis of the fragmentation patterns of compounds I—IV was facilitated by considering preferred secondary structures of several intermediates. Thus. both two and three dimen- sional SpeCieS Will be Shown. The fragmentation scheme as shown in Figure 54 is prOposed. The points at which each oom- pound enters the scheme are indicated. The protonated 12C4 .mnwspm cacao po% camcom Coflpprmemmpm .dm omsmflm Dc ~\E .6 CE .13 If. no NE 0 OJOI /l\ 3 \I/ N“ H QWJV 0 ~ 030 a mo w ONN ~\E o o W10 o a m w o w a VQN n\E ”0: 1V flO OlV 00m ~\E ;l o o +Plf(p(k 214 and 903 ions at m/z 177 and 133 are proposed as intermediates for the low mass ions. The formation of m/z 177 and 133 ions will be discussed. followed by a discussion of mechanisms leading to important low mass series. Figure 55 indicates the fragmentation mechanism of 18- crown-6 through which m/z 177 and 133 ions are formed. U1- traviolet photoelectron spectroscopy shows that the ioniza- tion of crown ether occurs at a nonbonding electron on the oxygen rather than a bonding electron of the oxygen or carbon (167). The preferred structure for the neutral molecule (168. 169) which contains two intramolecular hydrogen bonding between 0(1) and CH2(5) is shown in Figure 55. Presumably. hydrogen bonds have an important influence on the establish- ment of the secondary structure. Also. hydrogen bonds should enhance the probability of intramolecular hydrogen transfer which is shown as the first step. Following this step. the ring opens to form a linear intermediate. V. Figure 55 also shows intermediate structures through which protonated 1204 and 903 are formed. This mechanism parallels solution behavior. The acid catalyzed polymerization of ethylene oxide gives a distribution of crown ethers in which 12-crown- 4 is predominant. This is explained in terms of the second- ary structure of the polymer of the type (C2H4O)n which is helical. with one "revolution" of the chain occuring every 12 skeletal atoms. In solution. the polymerization reaction of ethylene oxide stops in a cyclization step after four 215 A ,o [“6130 (0614 315:) —- okflOJ O o g/~\o/~\<;;> Ho\/\o/\/o\/\o/\/O\/<> E E ”01' (m/ \ ONO + HQSA" 0 H3 0 O ._..\/ <;;>//\\6“A : 855 o o . o\J WHAT: 4.0m“— Wot EMU +1_ 0 O O/k < < l l o... 0 mm. C5 A .4 v o 220 pairs with one proton. Studies with other small atomic ions (172) such as Cr+ suggest that twp crown oxygens can interact with one ion. The interaction can bring parts of the mole- cule closer together for the formation of new bonds (smaller rings). Figure 55 shows that a number of products can be accurately predicted . It is shown that protonated 9-crown- 3 can result in proton bound complexes (of smaller ethers) which dissociate. This scheme not only predicts ions at m/z 89 and 45. but accurately predicts ions at m/z 73 and 61 as well. Thus. our results. and the results of Gray (152) for similar aromatic crown ethers. suggests the following: 1. Following ionization. an intramolecular hydrogen shift initiates ring opening. 2. Reclosure of the linear intermediate follows second- ary structures which are preferred in solution. 3. Most of the low mass ions are formed via m/z 133. It is expected that 9-crown-3 will give a similar mass spectrum. however this compound is not commercially available. Also. ions such as m/z 45 would not be expected from p-dioxane because no intramolecular hydrogen transfer via a six-membered ring would be expected. B. Mass Spectra of Unsubstituted Crown Ethers at High Sample Pressure 221 The mass spectra of these crown ethers are extremely pressure dependent. Tables 45 and 46 show the intensity of ion species of these compounds at two different sample pres- sure respectively. At high sample pressure the following observations can be found. 1. The base peak of III and IV is shifted from m/z 45 to m/z 89. 2. The parent ion and protonated parent ion (M+l) is formed. 3. The protonated ethers at m/z 177,133.89 are spe- cially intensified. All of these observations are due to the fact that the base peak. m/z 45. with a protonated ethylene oxide structure as shown previously. As the sample pressure is increased, the parent ion increases in intensity due to charge transfer, forming more parent ions. The intensity of the protonated parent ion is increased because the proton transfer occurs between a protonated crown ether and the neutral crown ether molecules. The evidence for a protonated ether is inten- sified due to the dissociation of the protonated parent ion and proton transfer between protonated ether and neutral fragments. .As m/z 177 and 133 signals increase in intensity. all of the fragment ions would be increased by the mechanisms shown in Figures 54 and 57 (m/z 105.89.73.61). These obser- vations may explain previously reported six ions mass spec- tra of 15C5 (149). in which m/z 89 is given as base peak. Table 46. 222 Principal Fragment Ions in the 70 eV Mass Spectra at High Sample Pressure of Crown Ethers. 1372321.? W 15”" 1806C 2107a 8:35:81... 41 5 5 5 6 CZHO 42 12 11 9 8 CZHZO 43 63 62 48 47 C2H30 44 34 32 24 24 CzHuo 45 100 100 92 95 C2H50 55 1 l 1 1 C3H3O 56 2 2 2 2 CjH“0 57 15 13 ll 11 C3H5O 58 23 21 19 20 CZHZOZ’C3H6O 59 14 18 18 21 C2H302.C3H70 60 2 1 2 CZH402 61 4 l l 4 C2H502 69 1 2 2 3 C4850 70 8 7 7 7 C4H60 71 10 13 11 12 C¢H70 72 24 18 18 20 C3H402’C4H80 73 46 59 43 48 C3H502.C¢H90 74 5 3 2 3 03H602 75 8 6 4 6 03H702 85 1 l 1 2 C4H502 86 12 11 9 10 C4H602 Table 46. 223 Continued. 12:31. 221.3“ M 1505b W 2107a 5333:2111... 87 45 53 45 51 C¢H702 88 33 4o 25 26 CuHBOZ 89 88 99 100 100 C4H902 90 4 5 5 5 C¢H1002 99 l 2 2 3 05H702 100 2 2 2 9 05H802,C,+H1+O3 101 16 20 16 16 C¢H503,05H902 102 6 5 4 4 C4H6O3’C5H1002 103 5 5 4 5 C¢H703,CSH1102 104 5 1 1 l C4H803 105 2 3 2 2 04H903 115 1 4 3 4 06H1102 117 5 2 8 9 C6H1302 131 l 10 5 6 06H1103 133 20 56 3o 34 C6H13O3 134 1 4 2 2 C6H14O3 177 0.5 3 6 7 08H1704 221 0.3 0.5 2 ClOH21O5 264 0.1 0.1 Cléquoé 265 3 0.1 012H2506 309 0.3 Cl4H2907 a12C4, 12-crown-4 c18C6. 18-crown-6 , M.W. , MOW. b d1505, l5-crown-5,M.W.=220 261‘" 2107, 21-0I‘OWH—7,M.W.=308 224 and the parent ion (M+) and protonated parent ion (M+1)+ appear in 18C6 (166,173). Ion cyclotron resonance (ICR) experiments were performed on the ions discussed above to confirm the fact that they are formed in part from reaction of m/z 45 at high pressure. ICR studies also reveal that m/z 43 protonates crowns and leads to many of the same products (173)- C. Mass Spectra of l8-crown-6 at Different Electron Energies A fragmentation path can be identified by the observation of metastable ions. but these are limited to reactions with lifetimes > 10 '6sec. IsotOpe labeling is another useful tool for determing the fragmentation mechanism. In the pre- vious report (148,150-153). both methods have been used to identify the fragmentation mechanism for substituted crown ethers. We attempt, here. to determine the appearance poten— tials of the fragment ions. With these. the decomposition pathways may be determined (174). The mass spectra of 18—crown-6 at various electron en- ergies between 10-100 eV are shown in Figures 58-60. The ion abundances (% of total ionization) of fragment ions at dif- ferent electron energies are listed in Table 47. and plotted in Figures 61 and 62. Comparing these results. the following observations can be made: 1. In all cases, the base peak is m/z 45. .A>¢ manmav wmwwmew Coppomam mSOflpm> pm coma Mo mnpooam mde was .wm mpsmflm Om. 0t 00. on; 0: 0m. 0w. .O_r_ .09 .00 cm .O.N .0m 0m O¢ .... _: ...1 ____. mm MN mm H >mm_ WV ... ..a a ...: _: >m®_ mv 225 L L __ 8 1 l0 ¢ 226 .A>m omuomv mmwmthm Coppowaw macapw> Pm coma Ho mspommm moms one .mm mpzwfim Om. .O.t .O.®_ eOm_ .OV. O_m_.Ow_ O: 00. 0m .8 .ON 0m On 0? _:. ..... . . _ mm mm mm __ >68 . me IIrUIUr Illl'lr 8 0 q. l0 q- "UIIIr 227 00. P P P .A>m ooanoov mmflwprm Coppomaw msowhm> pm coma Ho wnpomam mmme one 0t 00. 0m. .011 0m. 0w_ 0: 0n.0. .0.0 .00 ..0.N .oo mpsmwm 0000 0? Nb .__..1 G «D P P —d- P .. ..._ >600 .. ... . .mm__ m? P p D D P D P r p r p P p p P D u p n p 7 D ' ‘ P MN. 41 u. 1 q —q— mm : =.. p _ m P D 0? 1P b1 h P h D P D fink - L b Paul—D L— P "a _-"1 D ¢"———1W1 - q 1 E _ _ . mm. _ ms_ 8. _ ” >68 8 me 1 RD— 7 P h P D P— «P D w H? b <-- — u r "q—uuq 6 OOHIOH map CH mQOH pCmEthm Hmmflocflhm .m: manme 229 mommmo onuom m.0 N.0 4.0 4.0 m.0 4.0 4.0 00 onuom N004m:0 0.0 0.0 0.0 0.0 m.0 m.0 m.0 00 44-04 Noaa:0 s.m4 0.04 0.44 0.44 8.04 0.6 4.a 5.: m.0 0.44 :.04 0.4: as 04-04 N000:0 m.m 0.m s.m :.m :.m m.m 5.4 0.4 m.m mm 04-04 N04...:0 m.0 0.m 0.0 m.m 0.m 0.: 0.0 0.4 m.m s0 0m-w4 N000:0 4.4 4.4 4.4 0.4 4.4 0.4 0.0 0.4 00 0n-0m N0mm:0 4.0 4.0 4.0 m.0 m.0 4.0 4.0 mm 0n-0m mosmmo 5.0 s.0 s.0 5.0 s.0 0.0 s.0 ma 0n-0m moommo :.0 :.0 :.0 :.0 :.0 :.0 m.0 :u 00::0 :4-m4 mommmo 0.0 5.0 5.0 :.0 :.0 m.0 0.m m.m 4.5 m.0 m.m4 ms 000:0 04-04 N0:..m0 0.N 0.0 m.m :.m m.m m.m 0.4 :.4 4.m mm 04-04 0.0:0 5.4 a.4 0.4 4.4 s.4 0.4 :.4 0.4 4.4 4. onuom 00m:0 m.4 N.4 m.4 m.4 4.4 4.4 0.4 on 00.4 00.m 004 00 on 00 on 0: 0m 0m 04 04 :4 N4 0464\5 . 4663439480 .s: 64060 230 on: . m0m4000 0.m 0.m 0.0 m.m 4.m 0.4 4.4 mm4 . m044000 m.0 m.0 m.0 :.0 :.0 m.0 m.0 4m4 . N034.00 0.0 0.0 0.0 5.0 0.0 0.0 :.0 s44 . N0444400 m.0 0.0 m.0 m.0 0.0 m.0 m.0 m44 . momm:0 :.0 m.0 m.0 :.0 m.0 m.0 m.0 m04 . momm:0 m.0 N.0 N.0 m.0 m.0 m.0 m.0 :04 ~044mm0 . mosm:0 0.0 m.0 m.0 :.0 m.0 m.0 m.0 m04 N004mm0 . m000:0 :.0 :.0 :.0 :.0 0.0 :.0 m.0 N04 mommmo . momm:0 0.4 s.4 0.4 0.4 :.4 :.4 0.4 404 m0:m:0 0m mommmo 4.0 4.0 4.0 4.0 4.0 4.0 4.0 004 wa.< .0.m 004 00 0s 00 on 0: 0m 0m 04 04 :4 N4 04 ma\s .N-0eac4eaoo .a: 64060 231 .A>m :wv Hmflpcopoa mosmumma AN\EV Cow Pamswmnmm onuom :054000 0.0 :.0 :.0 m.0 m.0 6.0 4.0 s54 0:-0m m0:4000 6.0 6.0 6.0 6.0 4.0 4.0 :m4 60.4 00.0 004 00 on 00 00 0: on om 04 04 :4 N4 04 66\s .mI060040000 .6: 6406a 232 2. The molecular ion was not found. 3. The small protonated ethers at m/z 177, 133, 89, 45 are predominant fragments when the electron energy is higher than 20 eV. The approximate appearance potentials for various ions are listed on Table 47. Figure 61 shows that the molecular ion dissociates to m/z 45 and 89 directly at low electron energy (< 20 eV). The ion intensity of m/z 45 and 89 de- creases as the fragment ions such as m/z 43, 44. 57, 58. 59, 73. 87, are formed. These seems indicate that m/z 43 and 44 ions are produced from m/z 45 and m/z 57, 58, 59, 73, 87, come from m/z 89. As the electron energy is increased, the high mass ions (1.9. m/z 177. 133. 89. 87) increase in in— tensity. Table 47 shows that the decreasing and increasing ion intensities are not equal. Due to the inaccuracy of ion intensity measurement. the appearance potential measurement can not be used for exact identification of fragmentation mechanisms. The calculation of heats of formation of fragment ions are difficult due to the following reasons: 1. The appearance potential measured in HP-5985 GC/MS is not reproduced well. 2. The structures of neutral fragments are still unknown so the heats of formation are difficult to estimate. 233 ‘x4.°o.a. H 30- .. |_. ,.\° 20' - ._ ‘\ .6 \ - \° j E! I I 1 4* fl IO l2 l4 l6 l8 20 E1 ENERGY (eV) Figure 61. Ion abundance (% of total ionization) as a function of electron energy (in e“). 234 1 I I l 1 l l ' 4O - ‘ 30 . . 133(x10) o H .. '1 E4 ‘3 20 - 45 59(x4) - 89 10 '- [+3 73 - I 44 38 177(x10) 7 I 57 n I 1 l l I EI Energy (eV) Figure 62. Ion abundances (% of total ionization) as a function of electron energy (in eV) for 1806. 235 D. Mass Spectra of Some Linear Polyethers In the fragmentation mechanism of crown ethers, a linear polyether intermediate are proposed. If this is true, there should be some similarities in the mass spectra of crown ethers and linear polyethers. With this goal. the electron impact mass spectra of 4-EGDME and 3-EGDME were taken at 70 eV. The spectra are shown in Figure 63. The ion abundances and preferred composition of principle fragment ions are listed in Table 48. The results show the following interest- ing observations. 1. The spectra of 4-EGDME and 3-EGDME are essentially identical. 2. The molecular ion is not observed. 3. The highest mass ion of significance in 4-EGDME and 3-EGDME are m/z 177 and m/z 133 respectively. 4. The small protonated ethers at m/z 177.133.89.45. separated in mass by ether unit. CZH4O’ are predom- inant ions. 5. The base peak of both compounds are m/z 59. The ionization of a nonbonding electron on oxygen seems to start from second or third oxygen atom in both compounds. The fragmentation mechanisms shown in Figures 64 and 65 proposed. Due to the inductive effect, the oxygen attracts an electron pair to form m/z 59, 103, 147 or attracts one electron to form m/z 119 (Figure 64). Comparing the mass spectra of crown ether and linear polyether. It shows that 236 .hmnpmaanpweflc Hoozam mCmHzQPmHMP 0:6 0609640096840 406040 osmahnpwmapmp Mo wupommm mmme >600 62% .mo mhsmflm 00. .Ofi .00._ .00... .00.: .0m. .0m._ .0_r_ .0m_ 00 00 0% 00 0m 0? -. .44 . . mm. mo__ 06 _ 0M1. .... ...6: ._. 66..- .__. ._,_.... I\ m0. 9» .. /0\/\0/\/ 0\/\0/\/0\ mm .. 237 Table 48. Principal Fragment Ions in 70 eV Mass Spectra of Linear Polyether. 12:79:21.3“ 3W “M 5:23:13... 41 1 1 05w 42 1 1 cszo 43 7 8 C2H30 44 2 2 CéHuO 45 18 18 CZHEO 57 1 1 C3H50 58 33 29 03H60 59 100 100 C3H70 6o 4 4 cz‘Huo2 7o 1 1 cufiéo 71 1 1 04H70 72 1 2 cgnao 73 2 4 C¢H90 75 1 1 03H702 87 9 10 c48702 88 1 2 0411802 89 12 9 C¢H902 90 1 1 0.111002 101 1 2 0511902 102 3 4 05H1002 103 13 25 c H o 5 ll 2 238 Table 48. Continued. Fragment Ion 3-EGDMEa 4-EGDMEb Elemental (m/z value) Composition 104 l 2 04H803 117 0 0.55 05H903 119 0.55 0.35 05H1103 131 0 1 C6H1103 133 4 3 C6H13°3 147 0 0.44 C7Hl503 177 0 0.39 08H17O4 a3-EGDME. triethylene glycol dimethylether M.W.= 178 b4-EGDME. tetraethylene glycol dimethylether M.W.= 222 239 no. we + /\ Ol\/O\ a! .0... +\/0\/\0/\/0\ a. .szuMI: 0o sofipMPCosmmam 666 .0... +1. 666 w... .9420 .06 opswwm 240 (0+ \/\’\/0\/\O ’\/O\ /Ofi0~0%o/ .... 4- EGDME "‘x 3-EGDME ")2 I78 (1 a “0+ 90+ Hzcg C/ / 1 ”2; 1 H- 032 \OOI/I H—CQZ ,0 o h - o o (J: *2) 4“ = 0“) 0w C515) 0 ")2 I77 ")3 :33 FRAGMENTS FRAGMENTS Figure 65. Fragmentation of 4-EGDME and 3-EGDME to form protonated crown ether. 241 3-EGDME has the same predominant ions (m/z 45, 89, 133) as shown in 12-crown-4 and 15-crown—5, while, 4-EGDME has the same characteric ions (m/z 45, 89, 133, 177) as shown in 18- crown-6 and 21-crown-7. These similarities can be used to support our proposed fragmentation mechanism for crown ethers in which a linear polyether intermediate was proposed. Figure 65 indicates the mechanism through which m/z 177 and 133 are formed from 4-EGDME and 3-EGDME respectively. The protonated crown ethers are formed by a cleavage and ring closure procedures following the formation of the mole- cular ion. The fragmentation of protonated crown ethers is shown in Figure 17. According to the procedure. some ions such as m/z 45, 61, 73. 89, 105. are formed. From the correlation of the mass spectra of linear poly- ethers and crown ethers, the fragmentation pathways which we proposed are reasonable and possibly can be used to predict the fragments of other highly functionalized crown ethers. 5. Suggestions for Further Studies The following projects would be a logical continuation of this thesis work: (1) Study of the influence of ion pair formation on the chemical shift of thallium(I) salt in binary solution mixtures. (2) Investigation of the influence of ring size on the Tl+ ion complexation, 1.9. with 12C4. 1505. 2107, 2408 crowns 242 and with cryptands 0211, 0221 and C222. (3) Study of the kinetics of complexation in various solvents by dynamic NMR. (4) Study macrocyclic complexes of the T1+ ion in molten salt. (5) From the correlation of the mass spectra of linear polyethers and crown ethers. the fragmentation pathways which we proposed have proved to be reasonable. The mass spectra of DA18C6. DTl8C6 and D01806 can be used to compare with the fragments which are predicated by our fragmentation pathways. Also. other techniques, such as isotopic labeling, metastable ion analysis and appearance potential measurements may be useful for exact identification of fragmentation mechanisms. APPENDICES 243 APPENDIX 1 THE SIGN CONVENTION FOR NMR SPECTRA The position of an NMR signal (represented by a chemical shift ) is determined by the real magnetic field applied on the nucleus under study. A nucleus does not experiences the magnetic field which is applied to the sample (HO) but a field, H, which has been altered by the screening of the electrons surrounding the nucleus. Thus at the nucleus the magnetic field is H = HO (l-B) (A.l) The screen factor. B. which depends on the electronic envi- ronment of the nucleus is the sum of the various paramagnetic (8p) and diamagnetic terms (8d) (175) - B + B ‘CD I inter intra =3 +Bd+B inter p Bd + Bp (A.2) Where 8. lntra 1s the intraatomlc screening, while B. inter is the interatomic screening. The B. is generally very lnter 244 245 small ( < 2 ppm) and is usually neglected. The diamagnetic term (Bd > 0) is related to the diamagnetic currents due to the circulation of the electrons around the nucleus which leads to shielding of the nucleus. The second term, Bp is negative and is derived from the fact that electrons in a molecule are not always spherically symmetric about the nucleus. The presence of upaired electrons or p electrons near the nucleus is an important factor in determining 8p. A more representative equation for interpretation of a cation screeing factor in solution has been derived by Deverell and Richards (176). Chemical shift data are usually measured in a dimen- sionless scale in ppm (parts per million) from the chosen reference. With the inclusion of the shielding factor at constant HO. the Larmor equation relating to the resonance of a sample and a reference are = L - _ Y Where 7 is nuclear magnetogyric ratio, V8 and Vr are the Larmor resonance frequencies of the sample and reference respectively, BS and Br are the screening factors of the sample and reference respectively. The chemical shift is written as: up...) = —'~i—-———11 x 10 01.5) 6 N (Br - 88) X 10 (A.6) According to Equation (A.6), (VS-Vr) is proportional to (Br-BS) at constant Ho' so an increase in the resonance frequency implies a decrease in shielding for diamagnetic nuclei (8 > 0). In the older literature both possible sign conventions have been used. According to IUPAC recom- mendation (177). the sign convention in relation to the FT NMR data contained herein are plotted as shown in Figure 66. In the case of diamagnetic nuclei studies. the screening factor is positive. so the graphical presentation for the NMR signal at the right hand side appears to be small ppm. low resonance frequency. upfield and shielding. While. for paramagnetic nuclei studies, since the screening factor is negarive. the NMR signal at the right hand side appears to be small ppm. low reasonance frequency. upfield and deshielding. 247 (A) Diamagnetic nucleus (1H & 13C ) B > 0 S W REAL small 5(ppm) upfield shift shielding low resonance frequency high channel number high e density (B) Paramagnetic nucleus ( 23Na. 39K. 133Cs & 205Tl ) B < 0 S W REAL small 6(ppm) upfield shift deshielding low resonance frequency high channel number low e density Figure 66. .The sign convention.for NMR spectrum. 248 APPENDIX 2 DETERMINATION OF COMPLEX FORMATION CONSTANTS BY THE NMR TECHNIQUE: DESCRIPTION OF THE COMPUTER PROGRAM KINFIT AND SUBROUTINE EQUATIONS A. Determination of Formation Constants for a 1:1 Complex In the complexation reaction between crown (L) and thallium(I) ions (M+) in solution. the equilibrium for a 1:1 (metal ion:ligand) complexation reaction can be expressed as: The KINFIT computer program was used to fit thallium-205 and carbon-l3 NMR chemical shift Kg. mole ratio data to equation (3.10) which was inserted into the SUBROUTINE EQUATION: 2 2 _ T T 2 T 2 T 2 T T T aobs — [(KCM - KCL -l) + (K 0L + K 0M - 2K CLCM + 2K0L + T a 6M ‘ 6ML 2K0 + 1) J( ... > + 6 (3.10) M . ML 2K0M In order to fit this equation,two constants and two unknowns are used in the FORTRAN code: 249 U(l) = 6ML U(2) = K T CONST (1) = CM CONST (2) = 6M The two input variables are the analytical concentration of the ligand (0%, M) and the observed chemical shift (éobs’ ppm) which are designed as XX(l) and XX(Z) respectively in the FORTRAN code. Starting with an estimated values of K and 5ML’ the program fits the calculated chemical shift to the observed values by an iterative method. The data input includes the control cards and the NMR data. The cards include: (1) The first control card contains the number of data points [columns 1-5 (F 15)]. the maximum number of iter- ations allowed [column 11—15 (F 15)]. the number of con— stants [column 36-40 (F 15)] and the convergence to the tolerance (0.0001 works well) in columns 41-50 (F 10.6). (2) The second control card is a title card. (3) The third control card contains the value of 00NST(I) (0%. m) in columns 1-10 (F 10.6) and 00NST(2) (6M. ppm) in column 11-20 (F 10.6). (4) The fourth control card contains the initial estimates of the unknowns U(l) and U(2) in columns 1-10 and 11-20 (F. 10.6) respectively. (5) The fifth through Nth cards are the data cards which contain XX(1)= 0% in columns 1-10 (F. 10.6). the variance 250 on XX(l) in column 11-20. XX(2) [the chemical shift at XX(1)] in columns 21-30 (F 10.6) and the variance on XX(2) in col- umns 31-40 (F 10.6) followed by the same parameters for the next data point. Each card may contain two data points. The SUBROUTINE EQN and sample data are listed on the next page. 251 “Q‘ NNN 000 0 EEC C C C C C QC ) ) C C X9 0 9 C C AC9 0 5 C C VTT 3 0‘ C C TOP (,x c C ILO U09.- C C oZL F11 C C U I 0 9‘ 0 C C OPT TY) c c XoP 090 C C 'UC 0’s CH C RPM 30( C C he. (GI CC C UCT 031 CC C OFA Ft! CR C NOD OTC ) CF C 0PJ )8! a C C R0 0 0X) CS C AFT 000 T C: C V 0‘ 3).: N C) C 01C (0‘ A C2 C NIL P2P T C( C 0X. OTV) 8 CT C TDT FLTS N CS C P98 OAXI 0 CN C CF“ )VRC c CC C NYC 4C OX CC C .195 ‘1’X N c c RX. XECXF C C C CRT x 05 QY T C DC Ros c)()T T CNEC Ixc T0861 A Covc XXR 0211 H CCRC 909 0(P( R CNEC FFT BCST) O COSC AYC .TISZ F CCBC LTC 4 9 oh... C:OC 01V ())00 N C) C To. XCCCI 0 CISC USY T0501 I C(:C IPC XH3()O T CT)C 9E. X‘CTCC A cszc E .' X)L<~B.1 x CNCC FR . ‘OZCC ' E coxc AAJ T2¢kY9 L CCXC o Told pit) 0V. 9 Du C 0C 4 dvd 0U1)Y8 P C C CD 9 J 026 Q 9 0 C C M CIR Ho)01)7 C CK C P59 TTOC on... C:DC N AEL EF02051 . C)NC I TR. M03¢5Co )0 CZAC K NI 0T IK 9T(T:. 6/ C(GC =. GOVD I/QCSPQ cl CUIC h». CT.» 0 TT(ETC4 E/ C LC ow... h 9T CNXVSLO F/ C 0C 0 [UIQSEI 9N93 Al C CC ”MN tCQTTFOL)C)9 T/ CLhC m I IKTSSFFCICJ2ECIJ/ E E ECHCC otK . T Sxk/II205(U66((22 U U UC CC .ART. 4 UNEQCNNS.)C R:: T::NNNNNNCS:C CW“ 0 0T COTLCCCNCCTOIEEEAKPRIRIRIC:)C P:UF RMvA9vME21FTTPFTMNAUTUTUTC)1C ”NIYMN EFXVYMPH¢¢O NALIRUVTNTNTNC1(C WWW Myau hm m LCTGYCCIFYFOOTTRCOOEOEOECCCXC 0 0*: SCHIYCCOQDoGCIdiFNNRCRCRCCUXC AA W MLB 12... 12... C C anQunU m u 1 6 7 8 2C C U ' O c c CBSL LNAO 9 C C no.6 6666 a . . PJP 7 CCCC C)¢U(1) CON$T(1) T C 139(k‘ )GG (N)XCT)1$ XOZXCSICO) XCQCTRTUTI ((ctaCX-.. ti)’)CX)10 ))2))(a2.E 22(229)(Ek ..IU“)\ITFO ot(UU)ZS+fi .L. E C CH C E F. E r. ))t((2(.NAT US U U UT U U U U U 2200. i (COAENN:NNNNNNENNNNNNNNNNN l.‘ oU.uU(C(HRIDRIRIRIHRIFTRIRIRIR UU). o o... . ((IUTIUTUTUTIUTUTUTUTUTU (ls . 6:2 : .. : ((TNSTKTNTN‘.TNTNTNTNTNTD : .. : .. :ABC :FEOEF_CECCCF[CECEOECEOEN AECUEAECSIRCD‘RCRCRCIRCRCRCFCRCRE .NEo-l) GO TO 20 XX(2) 534509012 3 2 11.1 7 *i *‘IQO‘I'IHI-*‘I‘I§‘INI"INININI'I‘IHINI'ININI§§§*§"*§§§§§§§*§***§****§§*I* 9CMRD m A C E DT. 6 0m R CT mmsm %MML 606m WTmI DION CTCI {-I'I‘ININI‘I§*§*‘I§***INIHINIHI'INI.*§§*§§§§§§§§§**§§§§{fi'fl‘l’lfii‘G‘INI’I' ‘I’ IHANKCMRD DATA CARD 9cmm 252 (B) Determination of Formation Constants for 1:1 and 2:1 Complex The equilibria for this reaction can be expressed as + + M + L‘fi ML Kfi.- CML+/'cM-CL (A.7) ML++L~ML+ K =C +/c +-C (A8) 2 2 ML2 ML L ' Where C represents the molarity of the species, 0% and CE denote the total concentrations of the metal ion and ligand respectively. Then T _ _ 2 CM - CM + CM+ + CMLZ - CM(l + KlCL + KlKZCL) (A.9) CT=C+C++ZC =C+KCC+2KKCC2 L L ML ML2 L l M L 1 2 M L (A.lO) (A.9) can be rearranged as C = CT/ (1 + K C + K K 02) (A 11) M M l L l 2 L ' Equation (A.lO) can also be written as 2K K c 02 + o (1 + K c ) - CT = o l 2 M L L l M L Therefore -(1 + K C ) + [(1 + K C )2 + BK K C CT]% C _ l M l M l 2 M L (A 12) L_ O hKlKZCM 253 The observed chemical shift is: 5 = X 5 + X 5 obs M M ML ML + X 5 (A'l3) ML2 ML2 In order to fit the calculated result with the experimental data. an expression for the relative mole fractions of all three species in terms of CE and 0% is required. Two con- stants and four unknowns are used in the FORTRAN code: U(l) = K U(2) = K2 U(3) = 5M U(u) = am 1 2 T CONST(l) = CM CONST(2) = 6M The two input variables are the total concentration of ligand (0%, M) and the observed chemical shift (éobs’ ppm) which are designated as XX(l) and XX(2) respectively. In order to avoid determination of the solution to a cubic equation in order to obtain values of C and CL and thus M 6 , an iteration method was used. This method is achieved obs by applying a "do loop" in the EQN subroutine of the KINFIT program. The computer starts the calculation from given initial estimates for four unknows, and first calculates CL’ then used this newly computed CL value to calculate CM. Then, again these values are used to calculate CL and so on until the ratio of the previous CL to the current CL is almost equal to one. The iteration stops by "jumping out" of the do 100p when the difference between unity and ratio of the 251; new to the old CL values is less than 10‘5. Then the current CL and CM values are used to compute the mole fractions of each component and thus éobs The SUBROUTINE EQN and a sample data are listed on the following page. 255 .QQQ. .QQ‘ Q Ql.‘ .6 Q‘ ”MIN” NNNN N ”NS 8N RN 000°C 000° C CC; CC CC CCCCC CCCC C CC: CC 9?. O... 1 1 I. U D an.” u .. 9‘ 1L0 ”CC C C 1 oz... '11 C C 1 U 0 0 OT 0 C C C OPT 1" C C u A 00. U CC C C . OUU C)5 C C 2 Kurt" 301 Cl C C nu o 0 (C1 CC C I ”CT 031 C! C D OF! F‘X C C 1 N on. CT“ T C..- C 1 CPU ,3 O 0 CC C 1 IO 0 C31 CC C C IFT 000 T CF C TU '01 3)5 N C C 52 010 (DC I CF C "2 “1" P2P T CC C U 0‘ 0 OCT, 3 C C CC 101 FLT! I C.“ C a? ' Os OIX1 o C C T 05.“ 1V“... C C1 C11C ""0 4501 C2 C1(C It. 1501 P 0 CT C1.) CRT X .5 O T 1 CS CI 09 ) ) )2 N03 0)!) T T C“ C.QC 5 o 1? T‘C 1U“‘ 91 ‘ C02 C1 0 o 0 CH : I8” 5211 I CC“ C101 U D TD . o O o U(M‘ I C C11 0 1 1 C SC u. PPT 305T ) U C ) CT(CT 7 ) 2 G 2 No IVC 0T1: 2 F CoQ CST5. )9 1 c In 0 0) LT: QQON 1 CN( CNRoC 1. C 0 C3 9 CQ 01" T110 0 u CCU CDC) 0 T8 an 1 V2 1 1’1 ... o o 13....» 1 O C... C9311 I) I)N 01 N 120 " U57 T350 1 1 C m...- ‘1 a)! C CDC 1. To. _ 13.0 Cult-‘11 O T C“ 0 0U 01 12C 02 C .l C TO... 9‘9 COTTUOC ‘ C 1NCN1oN ”I 2!. 5. 15 o S)? . f.OT X)LSI.C1 '- C SUCU-DU OX (U) 2: 1n. \0 "NE: a. PI. 002C130 C CftTCCtflC Co UoZ o T C 2 DID} 2 ltd TZQNYCQ L CO) C :1 Co .0! 01 RN C CCC r TIJ P()oYFo P C 5LC)Ho) 1! B-U T: )10) U logo 6 J04 CU11T—r. H C OCTC‘JN” I. O o. 1 0‘11 0 TNT-l ol _ 030 J026910 m CU C1011 To ob) 08 1PTC ) "N3 : :1" H o) 01)? N ECTCCC N3 81.1 C! T In 1 (0‘0 0 _ F59 TTCCoCQI CD CCT TT 11 OI! C)I)§C T CCUC 5 " ICL CP0255)1 o CC...RCS)SS R o 2)U ) N . 2.2.. U o o o ) . TR. HDJ‘SCOO )0 . C KFCNCNN Do .8003)! 1T. oD)H)F) 2 ) u .51 OT 1K QTCTC... 6’ CL: C0 .00 C 8 o 0)] 00C 0 .1 o )I1N201 C 1 : C 0'.“ ’ICCS—P‘u O 0’ C‘TFCCCCC U1" ,1113 0,1,0 0| ”11°C, . C o . 5Tb o TT‘CTUIQ CI CTZOC o o o 0 3C. 6.311 .0115 o L l1TCU2 o I o _ 8 0T DNIVSLC 0 9’ COT CTCGTU on. on. o o U(C .15 o o 0 C15. 0 (C o C . CU1OSC1 0N0 3 II CTUoCLCCCo 3!NoooTCC-D)!) .TN))TNS S N _ cor OTTB Cmc)C)..u O T, C8 CC 0 o o .0 . 03-511)... oCNaNa-N ")55115 03 ... o IKTSSFP&13252i61JI C C ...—C, NC1111..UN.U1C1(NN1 0121‘11CN01NCTCWRHO CC C C Ch 9. C C C T SXHIITZQSTTUCGTCQZ U U UC11DC1111). EC.‘.(O1)C)F(FUO(OI UOTS US U U UT U U U W U _ UNC OONNS 0)....5 N: a T: 8NNNNNNCTKCCICCC1OO oT)T(CC(N : NFTFNCUCH ... CC:NN:NNNNHNCNNNNNNhuuNhrn " OUT LCOONO0TLOTCCCAKRR1R1R1CT 3 .. CXXXIC 8 UNI1K : 6 .. C(OC1111: O ......u12: H)R13~AT.A1R13 R1RTR TNT I1? : FE 05 a"HCZ1PCTTPPTHNIUTUTUTCS)HCCIXXF)ZCHIC) oQXC1FDHDT) ovHOPPSTZUTTUTUTUTTUTUTUTUT UTU .. E'IVTHHHCCOF ND‘1RUVTNTNTNCN1NCTCTCF1 CUSN1NCCTFCR‘NN1 CNHBCTTMHSTIHTHTHCTNTHT NTKTLTR- _ UUTCTUU1FT ”TUCTTCUCCCUCUCUCCCUCFFFF1TUFU .. 3 T 8 nut-FI'AFOFU‘ : 3UUUFXCUf.C-UCOEUFCU.LUC DCCCCCI" 5C b1nCCD1flmN-DGC1JUFNNICICRCCCUCC11110CUTFCSCDC11RU1FICCn-Ct. CCS1XRCRRCRC£ CTRCRCR Cd €6.63... 12 m. C C a: 1 C T I CC C U 0 On. 0 c. 3 a 5 n. o C 1 2 : C C 0 D 02 5 3 2 1 1 1 9; C C 1 C 22 2 76“" C C 1 CCC 9GARD "v‘vv -————v—— "' -—— INITIAL MINA?! CARD BUNK CARD CONTROL CARD TITLE CARD CONSTANTS CARD UTA CARD 256 APPENDIX 3 DETERMINATION OF ION-PAIR FORMATION CONSTANTS BY THE NMR TECHNIQUE; DESCRIPTION OF THE COMPUTER PROGRAM KINFIT AND SUBROUTINE EQUATION The equilibrium for ion-pair formation can be expressed as K. _ 1p _ M++X __.. M+'X and + _ +. — K zAgM-x)= (M-X) =K/v2 ip A + A - + - 2 c t Mex (M)(X)Y+ in which Ki , KC and Y: are the thermodynamic ion-pair P formation constant. the concentration equilibrium constant and the mean activity coefficient respectively. By using the well known Debye-Huckel equation, y: can be thus cal— culated as follows: -4.l96 x 106|z+z_|JI } = { I “I exp . £§33£1 + $24?) (A.ll+) In this equation 2+. z_ are the charges of the ions, I is the 257 2 0 0 O o l molar ionic strength which is 2 2 C i (C = concentration i 12 summed over all species in the solution). D is the dielectric constant of the solvent and T and g are the temperature (OK) and the closest distance of approach of the ions in X. The observed chemical shift is a pOpulation average of those of the free ion and the ion pair; i.§. 6obs = §FXF + 6ipxip (5F - sip)XF + 6. (A.15) 1P Where XF = [Li+]/C¥; and 0% is the total concentration of Li+ in the system. Meterial balance gives 0% [Li+] + [Li+-X-] = [Li+] + KCELi+]2 Therefore T -l t (l + uK C [Li+] = c M 2Kc. T s X _ £lé:J - -l + (l + hKCCM) K _ K 2 F ‘ T ‘ T and C ‘ i Y: CM ZKCC P So that, finally 258 T . -1 + (l + uKipCM y 2 obs T . F ip ip Three constants and two unknowns are used in the FORTRAN code: U(l) = 51p U(2)= Kip CONST(1) = 6F NIH CONST(2) = (DT) CONST(3) = 3 In these studies, g= 2.563, 6F: -l.5 ppm, (DT)%= llh.6 were chosen. The two input variables are the concentration of the salt (03, M) and the observed chemical shift (sobs’ ppm) which are designed as XX(l) and XX(2) respectively in FORTRAN code. Staring with an estimated value of 6ip and Kip' the program fits the calculated chemical shift observed values by an iteration method. The SUBROUTINE EQUATION and a sample data are listed on the next page. 1359 HAL. L*DYE. KINFT4?KINFT4. HAL . BANNER. LEE FTN, B=LGO. PNC CARD JOB CARD PASS WORD CARD RETURN.KINFT.LGO. LOAD, KINFTLP. LCD. 19. WITL r: 11 FF. “or. 11 KK or. y. ‘0 9 "7...! ‘9? 1L0 02L U '0 9P1 x 'P QUO KFM '1 99 U07 OFA NOD QPJ R0! AFT- v 9A 010 N1“ 9!. 9 .IDI D. 08 CF»... luv-o Colc RX 9 CRT- “ CC. IXC XXN Q Q Q “T AYC LqIE 91v 1 9 ’ “ISY. .IPD of. 9 'I. 0V- F9. 0. AAJ Tully JOJ CD 0 El." ps. ALI. TR 9 N1 OT 0 0V0 [1‘ Q N '1.- \l a .H CO) 3 o ( ()x URUR F1] '1‘ ' ’v’ c 'C 0": 301‘ ‘01 031 FIX OvID ’S Q 0’) o In 3.15 (0‘ P29 0") FLTS 'Auvrol \lvqtl‘ “C 0’ (l’x XLUX X .5 OP ')l\\IY ,ONbT 0211.7. Phatwnl‘ Q 1;((..|’ 01152 4 Q 0N1. (’)0 Q xqsn§C1 7'05 91 XU1.(’ 9 x ’(Tst. 902C( 9 T2 QNYO 5") 'VI 9 OUI’YQ. JOZID 9' H 0.) 91,7 TITO“. .0 9 EFP.ACH%C‘1 H03(5(9 1K 9T(.|5 [/4CSP 9 TT‘FTIC“ DNXVQCL. [U1 OSEI ON 93 N C Q'ITI: UN )C) 9 IKTp‘acrr'pc1cr.ylEr..‘od’ vl SXN//1298.(U66l\(22 U U UNEOONNSO)‘ Nz: 1::NNNNNN::IKK(((E UtlzNNNNflNNNHNNNNNNNNNN OOTLCCONCiTOIEEELFDFIRINI)’:::TTT: :C.DRIPIPIRIRIPIRIRIRIR PMCAOHME71PTTPPTNNAUTUTU713))KSS$A Ko(IU7UTUTUTUTU7UTUTUTU EHXVYPPP((O NAAIRUVTNTNTL((12HNNNH N4(STNTNTNTNTNTNTNTNTNTD UOTGYOOIPYMOOTTPOOOEOC.OEOXX((OOCOE O: :EEOEOFOEOEOEOEOF.OEOEN m SCHIYCCC0CQGCIJHFNHFCRCRCXXUUCCCCG CFSHRLRCPCFFECRCRCRCRCPE 0123 12‘. 1 A E 3 4 5 0 9 0 1 2 C 3 2 1 1 1 0, Ru CCCCCCCC 7 PAIR FORVATION CONSTANT *) ION . hFIfKCR CITGXRn/s .LrLanr 9),)! 9.CP.. f r... [ ... C. r... E E rl UCSOICIZSX (Cos U U U U U U U U U \I I i v \I L 3 E ‘ NK T O S IN N I 0 L c tart i .IR 9 EU 2 T1“?! 0 NN A nu AADP 5 00 Non. IIIEA t Tvlvalk) TAAPQCIGL FHMFN ( 1RD“ CRT HOCFCES. (LFFC TIN CMO LGthAC Auervpp‘ (II-111:4] TIRRHCP)’ FMIISE )‘l lrLAA LE1, HHPPLFC‘) TSC AINxz .L NNCDAX‘ ALGOL] .ll‘ql SANIIMISTS CI ENIRN FITCNHr.'.LCO OUMIIOCV Sn...) [HNI Lfiolq NHIATI 0000) o OCLNAEch 0’2 I] YRL(.AU1. TDGDTFFNOr‘i) o AENONFOOOXAII RVIULE law-yr“ ulnnRanrrcl Q‘EXT) 9F))/(2ofiCONKOXX(1)))fi(CONSI(1)-U(l))OU(1) ESAHO G QR‘OGI‘ CHEVTCSSA . nu. st .th O ......‘Q..Ia.l4un {flflflflifi“fl@iflflflflfflflfl§flflflfiflflflflIfflflflfflflflfifflflflflflfli CONTROL CARD TITLE CARD 9 CARD 8 GGWHHM##HHW*fflflflflflufiWHH‘WHMW‘HMGWNM%JMHHWNHMi§ BLANK CARD INITIAL ESTIMATE CARD 6 DATA CARD CONSTANTS CARD ll. 12. 13. 1#. 15. 16. REFERENCES C. J. Pedersen, J. Am. Chem. Soc., B9, 7017 (1967). N. S. Poonia and A. V. Bajaj, Chem. Rev., 12, 389 (1979). J. J. Christensen, J. 0. Hill, and R. M. Izatt, Science, AZE. 459 (1971). C. J. Pedersen and H. K. Frensdorff, Angew. Chem., Int. Ed. Englo ’ ii. 16 (1972). A. I. Popov, Pure Appl. Chem., fig, 275 (1975). J. M. Lehn, Pure Appl. Chem., £9, 857 (1977). J. J. Christensen, D. J. Eatough, and R. M. Izatt, Chem. Rev-o 15’! 351 (1971+). D. Midgley, Chem. Soc. Rev., h, 549 (1975). I. M. Kolthoff, Anal. 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