A specmoscomc STUDY 0:: me momma or PHENOL AND SELECTED ANOMANC- N ETHERS ON HECTORITE‘ Thesis for the. Degree arm 9.]. NORMAN SEATS UNIVERSITY , DENNIS B; PENN 1973 LIBRARY Michigan State University This is to certify that the thesis entitled A SPECTROSCOPIC STUDY OF THE ABSORPTION OF PHENOL AND SELECTED AROMATIC ETHERS ON HECTORITE presented by Dennis B. Fenn has been accepted towards fulfillment of the requirements for __Eh_LD_gdegree in _S_O_il._S_C_i_ence 77/W/iiflfizflj/ Dr. Max ; Major professor Date yjftvx‘ 5: / ? 7 3 0-7639 ABSTRACT A SPECTROSCOPIC STUDY OF THE ADSORPTION 0F PHENOL AND SELECTED AROMATIC ETHERS 0N HECTORITE BY Dennis B. Fenn The nature of the interaction of phenol and selected aromatic ethers with homoionic hectorite was studied by spectros00pic techniques. The only direct phenol-cation interaction observed occurred with Cu(II) or Ag(I)-hector- ite, where complexation occurred between the cation and the 'WLelectron system of the phenol molecule. Partial dehydration to uncover at least one ligand site on the cation was necessary before complexation would occur. Data obtained with a large number of other inorganic cations showed little or no direct phenol-cation interaction. Pos- tulated binding mechanisms of phenol on these systems include hydrogen bonding to the silicate structure, hydro- gen bonding through a water bridge to exchangeable cation, and weak ¢[If-electron interaction with the silicate struc- ture. Alkyl ammonium montmorillonites adsorbed phenol by ion-dipole interaction between the cation and the phenol molecule and by weak Intelectron and hydrogen bonding interactions with the silicate structure. Anisole was found 1 under d exposed a dimer which t ite. A anisole hectori anisole Ag(I)-h kinds 0: only am tion wi' formed 1 dineriza ether a1 C‘d(II).} of each single, eIECtror taming found to form a type II dfcomplex with Cu(II)-hectorite under dehydrating conditions. When this complex was exRosed to the atmosphere for several hours. it underwent a dimerization reaction to form 4,4'-dimethoxybiphenyl which then forms a type II complex with the Cu(II)-hector- ite. A reaction mechanism is proposed. Physically sorbed anisole and a type I qrcomplex are also identified on Cu(II)- hectorite. Ag(I)-hectorite formed a type I’H’complex with anisole. No physically bound anisole was present in the Ag(I)-hectorite system. Adsorption of anisole on all other kinds of homoionic hectorite studied was by physical means only and is independent of the cation, indicating associa- tion with the layer silicate surface. Butyl phenyl ether formed a type II’N’complex with Cu(II)-hectorite, but no dimerization reaction was noted in this system. Phenyl ether and benzyl methyl ether form a type I? «(complex with Cu(II)-hectorite. No type II analog was noted. ESR spectra of each of the ether-Cu(II)-hectorite systems showed a single, narrow band near the g value of a ”free” spinning electron. Both the type II complexes and the systems con- taining only the type I complex exhibited this ESR band. in A SPECTROSCOPIC STUDY OF THE ABSORPTION 0F PHENOL AND SELECTED AROMATIC ETHERS ON HECTORITE By ‘OJ‘ Dennis Bl Fenn A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of CrOp and Soil Sciences 1973 Th wi W0 TO JACQUE This thesis is dedicated to my wonderful wife. Without her support, encouragement, patience and active interest this thesis would have been an impossibility. ii The a1 professor, stimulating stant suppi in the SCit inspiratio: Since: ance commi‘ Pinnavaia, my behalf. Appre< Cree and s< for the mar Thank; ing this m; ACKNOWLEDGMENTS The author eXpresses sincere appreciation to his major professor, Dr. M. M. Mortland, for his active interest, stimulating discussions, enlightening suggestions and con- stant support during this study. His knowledge and interest in the science of clay surface chemistry has been a great inspiration. Sincere thanks is expressed to the members of my guid- ance committee, Drs. B. G. Ellis, B. D. Knezek, T. J. Pinnavaia, and T. A. Vogel, for their time and effort on my behalf. Appreciation is also eXpressed to other members of the Crop and Soil Sciences Department and the Chemistry Department for the many opportunities for intellectual growth. Thanks is expressed to my wife for her efforts in typ- ing this manuscript. iii INTRODUCTI LITERATURE Gener Spect Arene Pheno Aniso ENTERIALS . Clay: Homoi. Clayj Clayd X-ray Elect; Infra; Elect; RESUL'l‘S AN] Phenol ‘ J i TABLE OF CONTENTS INTRODUCTION . . . . LITERATURE REVIEW . . . General Clay Organic Interactions Spectroscopic Techniques Arene Complexes . Phenol Adsorption Studies Anisole Adsorption Studies MATERIALS AND METHODS . . Clay Sample . . . Homoionic Clay Suspensions Clay Film Preparation . Clay-Organic Adsorption X-ray Diffraction . . Electronic Spectra . Infrared Spectroscopy . Electron Spin Resonance RESULTS AND DISCUSSION . . Phenol Study . . . X-ray Diffraction Infrared: Cu(II) and Ag(I) Electron Spin Resonance Spectra Ultraviolet-Visible Spectra Infrared: Other Kinds of Homoionic Hectorite Infrared: Substituted Ammonium Montmorillonite Aromatic Ether Study . Adsorption of Anisole on Homoionic Hectorite Identification of Green Complex Ultraviolet~Visible Spectra iv PAGE An. Oti El SUIN‘ARY AND I LITERATURE C PAGE Anisole on Other Kinds of Homoionic Hectorite . . . . 57 Other Aromatic Ethers on Homoionic Hectorite . . . . 58 Electron Spin Resonance Spectra . . 64 SUMMARY AND CONCLUSIONS . . . . . . . 67 LITERATURE CITED . . . . . . . . . 7O TABLE Assi tion phen a ph Cu(I coor or A Chan (\)I plan aren smec stat TABLE 1. LIST OF TABLES Assignments of selected vibra- tional frequencies (cm' ) of phenol in the solid state, as a physically bound species on Cu(II)-hectorite, and as a coordinated ligand on Cu(II)- r or Ag(I)-hectorite . . . Changes in the C-C stretching (\ll9a) and the CH out-of- plane (’TlOb) vibrations of arenes on Cu(II)- or Ag(I)- smectite compared to the liquid state . . . . . . Selected infrared bands (cm’l) of homoionic hectorite exposed to phenol and P205 for 2“ hours and then heated to 100° for one hour under constant degassing Selected infrared bands (cm'l) of three ammonium cations on montmorillonite after 24 hours exposed to phenol and P205 Assignments of selected vibra- tional frequencies (cm'l) of anisole as a liquid, as a physically bound species on all kinds of homoionic hectorite studied, as a type I ligand on Cu(II)-hectorite, and as a type II ligand on Cu(II)-hectorite vi PAGE 29 36 ’43 4h 50 FIGURE 1. Infr hect trea and then hour sing Infn hect ment: phen. to 11 conS‘ line‘ ESR : Cu(II LIST OF FIGURES FIGURE ’ PAGE 1. Infrared spectra of a Cu(II)- hectorite film over (A) no ' treatments: (B) phenol only; and (C) phenol and P205 and then heated to 100° for one hour under constant degas- Sing 0 O C I O O O O C C C 27 2. Infrared spectra of a Ag(I)- hectorite film over no treat- ments (dashed line) and over phenol and P20 then heated to 100 for on hour under constant degassing (solid line) 0 o o o o o o o o o o 28 3. ESR s ectra of freeze dried Cu(II -hectorite over (A) no treatments: and (B) phenol and P205 0 o o o e o o o o o no a. Ultraviolet-visible spectra of (A) Cu(II)-hectorite deposited on a quartz disk and exposed to phenol and P 05 for 10 days; and (B) phenol dissolved in distilled water . . . . . . . . 41 5. Infrared spectra of (A) liquid anisole; (B) an air dry Cu(II)- hectorite film; (0) physically bound anisole on Cu(II)-hector- ite; (D) type I (tan) anisole complex on Cu(II)-hectorite; (E) type II (blue) anisole com- lex on Cu(II)-hectorite and IF) type II (green) 4,4'-dimeth- oxybiphenyl complex on Cu(II)- hectorite . . . . . . . . . 47 vii LIST OF FIG~ FIGURE 6. 10. KBr P cryst extra hecto Ultra“ (A) a: tillm II an) compli (C) e: oxylr compl« Infra: over I (B) a] and P; Cu(II. Infra: butyl phenyl ite a1 ether P205; butyl ESR S] NBCtoj (B) a: plex) OXyb i] Phenyj Compli and p; Phenyj Plex) LIST OF FIGURES -- Continued FIGURE 6. 10. PAGE KBr pellet infrared spectra of crystals distilled from methanol extract of green, type II. Cu(II)- hectorite complex . . . . . . . 53 Ultraviolet-visible spectra of (A) anisole dissolved in dis- tilled water; (B) blue, type II anisole-Cu(II)-hectorite complex (dashed line);.and (C) green,_type II_4,4'-dimeth- oxyliphenyl-Cu(II)-hectorite complex . . . . . . . . . 56 Infrared spectra of (A) anisole over Ag(I)-hectorite and P20 : (B) anisole over Na+-hectori e and P 0 : and (C) anisole over Cu(III-gectorite and P205 . . . . . 59 Infrared spectra of (A) liquid butyl phenyl ether: (B) butyl phenyl ether over Ni(II)—hector- ite and P202: (C)butyl phenyl ether over g(I)-hectorite and P205: and (D) type II (purple) butyl phenyl ether on Cu-hectorite . . 62 ESR spectra of freeze dried Cu(II)- hectorite over (A) no treatments: (B) anisole and P205 (blue com- plex): (C) green, h,4'-dimeth- ‘ oxybiphenyl complex: (D) butyl phenyl ether and P205 (purple complex): (E) benzyl methyl ether and P205 (brown complex): and (F) phenyl ether and P205 (green com- plex) . . . 3 . . . . . 66 viii- Clay pounds to properties importance pie organi often stro organic ma build soil and aerati between so or fertili that can n In in large, seal cents, P01 Clay- pathV'ays. 0f the int matter, I Plete know matter its and S°mEti INTRODUCTION Clay minerals interact with numerous organic com- pounds to form complexes of varying stabilities and pr0perties. These interactions are often of great importance in nature and industry. In soils, for exam- ple organic matter in various stages of decomposition is often strongly adsorbed to clay minerals. This adsorbed organic matter helps to stabilize soil aggregates and build soil structure, thus greatly influencing the moisture and aeration properties of the soil. Also, the interaction between soil clay minerals and applied organic pesticides or fertilizer has proven to be an important consideration that can not be overlooked. In industry, clay-organic complexes are utilized on a large scale in cosmetics, paints, paper, medicine, lubri- cants, pollution control systems, etc. . Clay-organic research has deveIOped along two major pathways. The first approach has been to study the nature of the interaction between soil clays and soil organic matter. This important work has been handicapped by incom- plete knowledge of the actual composition of the organic matter itself, making interpretation of results conditional and sometimes ambiguous. Progress is being made in this area, however. The second approach has been to study the complexation between pure clays and simple organic com- ‘pounds, deducing the nature of their interaction from the changes in certain properties of the compounds. This second method has resulted in considerable knowledge about the binding mechanisms of organic molecules on clay sur- faces and has found many new industrial uses for clay- organic complexes. This study utilizes the latter approach. Research into the variables contributing to the physical and chemical properties of clays has shown that the type of exchangeable cation occupying the exchange sites of the clay is often a major determining factor. Transition metal cations contain unfilled g electron orbitals and possess relatively strong coordinating pro- perties compared to the alkali and alkaline earthymetais.. Studies on the interaction between the clay surface, the exchangeable cation, the cation hydration sphere, and other organic and inorganic ligand molecules are being conducted by numerous clay surface chemists. Developments in the last decade have shown that infra- red spectroscoPy is perhaps the most potent single method for evaluating interactions between organic molecules and the silicate surface. The method allows for the in,§itg observation of the interaction between atoms at the clay surface and does not require the long range repetitive regularity necessary for detailed X-ray analysis. One important hindrance in the method is the fact that min- eral lattice vibrations dominate certain portions of the Spectrum. The design and use of special cells with temperature and vapor pressure controls have been an important_development in infrared studies of clay-organic complexes. Infrared spectroscopy was an important tool utilized inthis study, along with X-ray diffraction, ultraviolet-visible spectrosc0py and ESR spectroscopy. In conducting this study we attempted to answer the following questions: (1) How are phenol and anisole adsorbed and retained on the clay surface? (2) What is the effect of type of exchangeable cation on the adsorption of phenol and anisole? (3) How effectively can phenol and anisole com- pete with water for coordination sites on the cation? (h) What reactions, if any, involving phenol or anisole are catalyzed by the clay system? Substituted aromatics are an important constituent of soil organic matter and hence are important in the associa- tion of organic matter with soil clays. Many industrial processes produce phenols as a constituent of the waste products, and as a result many rivers and lakes show appre- ciable phenol contents. Information on the mechanisms of adsorption of these compounds on soil clays and bottom sediments can be of great value in understanding clay- organic interactions in nature. LITERATURE REVIEW General Clay-Organic Interactions. Numerous reviews of clay-organic complexes can be found in the literature. The important binding mechanisms involved in clay-organic complexes were reviewed by Mortland (1970). He found the following mechanisms docu-' mented in the literature: (1) cationic, including ion exchange by organic cations, protonation of organic mole- cules at the clay surface and hemisalt formation: (2) ani- onic: (3) ionsdipole coordination: (4) hydrogen bonding, including water bridging, organic-organic hydrogen bonding, and hydrogen bonding to surface oxygens and hydroxyls: (5) van der Waal's attraction: (6) pi bonding: (7) entropy effects: and (8) covalent bonding. The nature of the organic molecule, the kind of exchangeable cation, the type of clay mineral and the degree of hydration are all important factors in determining which of the binding mechanisms will operate in a given system. Greenland (1965) has also reviewed clay-organic bonding mechanisms. Brindley (1970) in a review of clay-organic complexes pointed out the importance of the nature of the clay mineral in organic complex formation. Smectites and vermiculites have been extensively studied: but kaolinite, halloysite, and many non-silicate layer structures have recently been shown to take up organic molecules. Brindley points out the importance of residual water in the association of organic molecules and exchangeable cations. In some cases organic molecules are protonated by disproportionation of the residual water on the cation, and in other cases a hydrogen bonded “water bridge" has been shown to form between the organic molecule and the hydrated cation. Brindley reviewed literature showing that small polar molecules can form complexes on the clay surface by salvat- ing the exchangeable inorganic cations, but when polarity arises from -NH or -OH groups hydrogen bonding may also be involved. The importance of quantitative methods for establishing the number of adsorbed organic molecules per unit cell is emphasized by Brindley in his review. Theng (1971) reviewed the mechanisms of formation of colored clay-organic complexes. He concluded that most color reactions of clay can be ascribed to a charge transfer reaction between the mineral and the adsorbed species. The active sites on the clay were found to be aluminum exposed at crystal edges and exchangeable transition metal cations in the higher valency state, both of which can act as electron acceptors. The nature of the exchangeable cation, the solvent, and the pH of the system influence the rate and intensity of color formation. Theng also concluded that the mechanisms underlying the formation of colored clay-organic complexes are analogous to those involved in the polymerization of adsorbed organic monomers by clays. Theng felt this indicated the wide applica- bility of the charge transfer theory to the activation of organic species at clay mineral surfaces. n> Suite (1971) reviewed the Japanese literature on clay-organic complexes. Japanese researchers have investi- gated many of the colored clay-organic complexes found in Theng's (1971) review, as well as clay-organic polymers, effect of the type of clay mineral on complexation, industrial applications of clay-organic complexes, humic acid-clay complexes, and the structure and orientation of . adsorbed molecules. A text by van Olphen (1963) also describes various aspects of clay surface chemistry. Numerous Australian, English, and Russian labora- tories, among others, are studying clay-organic complexes. It is obviously not a narrow, isolated field of endeavor, nor one of minor importance or application. Spectroscopic Technigues. The study of clay-organic complexes has been greatly enhanced by the development of various spectroscopic techniques of study. X-ray diffraction has long been a' widely used tool in clay research. As an example of its usefulness in clay-organic studies, Greene-Kelly (1955) used X-ray diffraction to determine the orientation of aromatic compounds adsorbed on montmorillonite. From X-ray spacings Greene-Kelly was able to show that two orientations are common. The first, generally stable at low surface concentrations, had the plane of the ring of the aromatic molecule parallel to the silicate Sheet. At higher surface concentrations the molecules reoriented so that their planes were perpendicular to the plane of the silicate sheet. Greene-Kelly also showed that the contact distances between the surface oxygens of the sili- cate sheet and the atoms of the organic molecules are shorter than the normal van der Waal's distance. The most powerful tool to date for studying clay- organic complexes is infrared spectrosc0py. The theoret- ical basis for infrared spectroscopy has existed for more than fifty years, but only in the last fifteen years have instruments and sample preparation.procedures,beeno developed for use on a practical basis in clay-organic studies. Sidorov (1956), in an early work using infrared spectroscopy to study adsorption of small molecules on porous glass, found that adsorption occurred on two types of sites. One site was the surface OH group (as shown by the shifting of the ‘0 0H band), and the other was tentatively identified as the surface silica atoms. Upon adsorption, the o Edam opwuopoonuaHHvso a mo savanna cousamcH .H oaswwm 7.5 «5252 “>4; 3. . a. . s. or. 3... .s......a. safe... is... .s... is... .8... .e... ‘ d c 1 1 d 1 1 q q 1 o .8. 8o. . 2 § NOISSIIISNWI x z 2 x :2 2. no! 2. \ -‘\-- own . I: 11 . -'--.-- ’ L r (D! p D 80 02. 8. 8m 82 8. . 8a. L om: &...&2.8.2 8.2. . 88 7.5 «$95: was 28 NOISSIWSNVUI S .Aocaa eaaoov mcaoosmoo pampmcoo some: use: one new oooa op mouse: con» momm and Hoconn uo>o was Aocwa monmduv mucoEpaoup o: uo>o SHAH opauOPoozufiva< m we appoogm vopwumcH .m ouzwfim 7.5 £523 u><3 8: 8: 88 8: 83 1%we-@.§.€.§o§.§.§-§_§a§_§_§a *3 NOISSIWSNVUI S 8. 29 Table l: Assignments of selected vibrational frequen- cies (cm‘l) of phenol in the solid state, as a physically bound species on Cu(II)-heCtor- ite and as a coordinated ligand on Cu(II)- or Ag(I)-hectorite. Physical, Ligand, Ligand, Solid* Cu(II) Cu(II) Ag(I) No.* Assignment* 691 694 694 696 (3'4 ring stretch b2 754 759 786 783 firlob CH out of plane b2 812 810 808 814. «012 x sensitive al 888 --- --- --- qu7b CH bend b2 1152 1155 1153 --- 39a CH bend b1 1169 1171 1171 1169 189a CH bend al 1230 1214 1209 1212 Area with ring stretch character 1252 --- 1278 1273 A 7a X sensitive al 1370 1349 1346 1348 ~014 ring stretch with 0H character 1473 1470 1459 1462 \Q19b ring stretch bl 1501 1496 1484 1487 ~~019a ring stretch a1 1598 1594 1591 1592 ‘Naa ring stretch b1 3043 -—- --- --- ~913 CH stretch b2 3070 --- --- --- V2 CH stretch bl 3225 --- 3510 3480 CH stretch *Band frequencies and assignments taken from Green (1961) and Evans (1960) . 30 present on the clay as evidenced by the H20 deformation band at about 1620 cm'l. This is primarily water coordinated to the Cu(II) ions. The phenol adsorbed, therefore, is not interacting directly with the Cu(II) ions, but with the silicate structure and the cation hydration sphere. Simi- lar spectra were obtained with phenol adsorbed on hectorite saturated with a variety of different exchangeable cations, i.e., Co(II), Ni(II), Fe(III), A13+, Ng2+, Na+, and Li+. As seen in Table 1, each of the vibrational modes involving the phenolic OH group undergoes energy shifts when phenol is physically bound on the clay. It is apparent that the OH group of phenol is involved in the binding process of phenol on hectorite. The highly associ- ated solid phenol exhibits an OH stretching vibration at 1 3225 cm' while the monomeric phenol vapor absorbs at 3661 cm'l. The OH stretching region of phenol physically bound on Cu(II)-hectorite, shown in Figure 1B, has a 1 very broad band centered around 3500 em“ but tailing toward the lower frequencies as far as 2700 cm"1. Coordinated water is still present on the cation and is absorbing in this region as well. The broadness of the band, however, is an indication that several binding mechanisms of different energies, involving water and the hydroxyl group of phenol, are operating. In the absence of water the OH stretching vibration of adsorbed phenol, as seen in Figures 10 and 2B, is a broad band centered near 3500 cmal, which is 31 intermediate between solid phenol and monomeric phenol vapor. Farmer and Russell (1971) report a peak at 3480 cm‘1 in monohydrated hectorite which they attribute to the 0H stretch of water molecules hydrogen bonded to oxygen of the Si-O-Si structure linkages. It appears likely, therefore, that hydrogen bonding of phenol to the oxy- gens of the silicate structure, Si >M© is an important physical binding mechanism. Farmer and Mortland (1966) and Farmer and Russell (1971) report that treatment of a Mg2+-smectite with pyridine diaplaced almost all of the outer sphere of coordinated water, giving the following ionic complex involving a water bridge: H a 1: Mg---( -Hb--~NC5H5)6. (2) The OHb group of the coordinated water formed a strong hydrogen bond with pyridine and absorbed in the infrared 1 at 2800-2850 cm' , while the:absorption due to the 0113 group occurred near 3630 cm'l. The location of the OH stretching vibrations in this mechanism are very much a function of the hydration properties of the cation. As seen in Figure 1B, water is still present on the hectorite flaw V. {.1 32 even after adsorption of the phenol. It appears likely that the coordination of phenol to the exchangeable cation through a water bridge, 1_ Ha H . MEt-A-Hb---d—<::::> . (3) is another possible physical binding mechanism. Dowdy and Mortland (1967, 1968) studied the interactions of alkyl alcohols with clay surfaces and report that alcohols can compete with water for ligand positions around the cation and that the OH stretching band of directly coordinated alkyl alcohols is a function of the exchangeable cation.‘ These results suggest that direct coordination of phenol to the exchangeable cation, aft—Q (4) is another_possib1e interaction. Phenol, however, was unable to compete with water for direct coordination sites on any of the exchangeable inorganic cationsostudied, with the exception of Ag(I), without the aid of Péos dessicant. Also, the OH stretching vibration of physically bound phenol on Cu(II)-heetorite, Figure 1B, does not differ significantly from the OH stretching vibration of phenol physically adsorbed on the other homoionic hectorite systems studied.» Therefore, it is concluded that direct coordination of phenol to the exchangeable cation through the oxygen of the hydroxyl group, as shown in Diagram 4, does not take place. 33 Phenol is known to form dimers and polymers. Huggins and Pimental (1956) report that the OH stretching vibra- tion of the phenol dimer, ©jm-© ; a) occurs at 3484 cm’l. It is possible that adjacent phenol molecules, bound to the surface by one of the previously mentioned mechanisms, could dimerize and contribute to the infrared adsorption in the OH stretching region. Compared to solid phenol, the CH out-of—plane (7’lOb) and C-0 stretching (‘08a and‘Ql9a) vibrations undergo an fiv5 cm.1 ushift when phenol is physically bound to Cu(II)- hectorite, Figure 1B. These shifts cannot be explained solely on the basis of hydrogen bonding of the hydroxyl group and suggest that a weak'nielectron interaction exists between the phenyl ring and the silicate structure. Mortland 1 shift in the CH out- and Pinnavaia (1971) noted a 13 cm- of-plane vibration of benzene physically bound to montmor- illonite, which they attribute to’nielectron perturbation. The CH out-of—plane vibration is known to be quite sensitive to perturbations of the‘nielectron cloud. It thus appears that phenol is physically sorbed by weak’fl‘electron interaction with the silicate oxygens accompanied by hydrogen bonding to the silicate oxygens, intermolecular hydrogen bonding and/or hydrogen bonding to water molecules directly coordinated to the exchangeable 34 metal cation. Figure 10, Cu(II)-hectorite over phenol and P205, and Figure ZB, Ag(I)-hectorite over phenol and P205, are very similar and represent phenol as a coordinated ligand on the exchangeable cation. The CH out-of-plane (q’lOb) vibration undergoes a high_energy shift of 32 cm"1 on Cu(II)-hectorite and 29 cm"1 on Ag(I)-hectorite compared to_solid phenol. These results are definite evidence for ”wfielectron interaction between the exchangeable cation and the phenol. Karagounis and Peter (1959) studied the infrared spectra of phenol adsorbed on several salts including AgI and AgCl. The C-C stretching vibration near 1500 cm"1- (‘Ol9a) was shifted down about 5 cm-1 on all of the salts studied. This contrasts with the data here where the same. band was shifted down about 14-17 car1 on Ag(I) and Cu(II)- hectorite. The shifts obtained in this study on hectorite with other types of cationic saturation, however, were similar to those obtained by Karagounis and Peter. The uniformity of their infrared spectra, regardless of the kind of salt used as an adsorbant, suggests that Karagounis and Peter were not obtaining 1rcomplexes and that the sur- face of the smectite provides a unique environment for such interactions. The partial dehydration of the Cu(II) ion by P205 has evidently exposed coordination sites on the cation and 35 allowed interaction between the lowest unfilled orbitals of the metal and theqT-electrons of the phenol. Doner and Mortland (1969) and Mortland and Pinnavaia (1971) reported that the degree of hydration greatly affected the chemisorption of benzene on Cu(II)-montmorillonite and that partial dehydration of the Cu(II) must occur before a complex will form. Complete dehydration, however, will prevent complexation, as reported by Yariv, et. a1. (1968), while studying the sorption of aniline on mont- morillonite. Clementz and Mortland (1972) studying benzene adsorbed on Ag(I)-montmorillonite reported that benzene can successfully compete with water for ligand sites on the Ag(I) without degassing or P205 dessication, but only a type I complex is formed. . Pinnavaia and Mortland (1971) reported that the pres- ence of alkyl groups on the benzene ring restricted the complexation with Cu(II)emontmorillonite to the type I analog only. Clementz and Mortland (1972) report that Ag(I)-montmorillonite will only form a type I complex a with arenes. Table 2 compares their results with benzene and methyl substituted benzenes with the phenol data of this study. It is readily apparent from the analogous shifts in the C-C stretching (<019a) and CH out-of—plane (Q'lOb) vibrations that phenol forms a type I’nicomplex with Cu(II) or Ag(I) on hectorite. 36 mannawm>m so: mpmu** wasposnpm oeMOHHHm mo cowpmpnw> m an connomno .3. onQEoo meoncon H o8? nom?qO acumng pmooxo Amnmav vcmapuoz was uPCoEoHo Scum Coxmp spam 9 Hoconn pmooxo Aammav pcmavnoz use mwm>mccfim anm smxmv spam m mm as NH as osonsonaaeem * *mm m 0H encampfimoz on :m ma 3H ocoazxin on an m m ocoaaxis mm on as NH oaoaaxuo mm on m m ososaoe mm can m cm ocoucem on an ea as Aeaaomv accord anvm< eAHHvso nAHVm< eAHHVso essoasoo .3 .3338 32 osaaaeoeso 50+ A? :50 .AMmHZ 33¢qu 0:00: A H .opupm candfia one 0» mouse :aoo ovavoosmiava< no :AHHvso so mucous mo msowvannw> Apoatbv occaaumoueso so or» one Andante msaaoeoneo 0.6 one as nonzero .N oases 37 Figure 2 shows that only one form of adsorbed phenol is present on the Ag(I)-hectorite. Unlike on the Cu(II)- hectorite, no physically bound phenol is formed on Ag(I)- hectorite. Phenol coordinated to the monovalent Ag evi- dently covers the interlamellar surface area and blocks the physical adsorption sites on the silicate structure. In addition, unlike on the Cu(II)-hectorite, phenol is able to compete with water molecules for ligand positions around Ag(I) without the aid of P205, although adsorption is faster under dessicant conditions. The Ag(I) has a much lower salvation energy than Cu(II), accounting for the ability of phenol to displace the water. Pleochroic studies on the Cu(II) and Ag(I) ligand phenol systems showed that the C-C stretching (Q 19a) vibration, an in-plane vibration where the dipole change is in the plane of the molecule, undergoes a 50% increase in absorption when the orientation of the clay film is changed from 900 to 40° with respect to the spectrophoto- meter beam. This suggests that the phenol molecules are oriented in the interlamellar regions at an angle more toward the vertical than the horizontal. Stability studies on the Cu(II)-hectorite showed that ligand phenol is stable at 200°C but decomposes at 300°C as evidenced by infrared spectroscopy. The ligand phenol also is unstable in the open air. Atmospheric moisture replaces ligand phenol and after a few hours of exposure to 38 room air conditions the infrared spectrum of Figure 1C will become identical to the spectrum of Figure 1B, indicating a loss of all ligand phenol. Stoichiometric studies on the Cu(II)-hectorite-type I phenol complex, Figure 1C, indicated that a total of about five molecules of phenol are adsorbed on the hectorite 2+ ion. This value contains both per exchangeable Cu ligand phenol and physically bound phenol. It was not possible to determine the coordination number for ligand phenol alone on Cu(II)-hectorite. In the Ag(I)-hectorite system, however, Figure 2B, where only ligand phenol is present, the stoichiometry is on the order of one mole- cule of phenol adsorbed per exchangeable Ag+ ion. Electron Spin Respnance Spectra. The ESR spectra of freeze dried Cu(II)-hectorite and of the type I phenol-Cu(II)-hectorite complex are shown in Figure 3. Both the g” and g‘L components of the d9 Cu(II) ion signal are apparent in Figure 3A. In Figure 3B, however, the Cu(II) signal has disappeared and only a single narrow signal with a g value of 2.0023 is found.. The g value for a ”free spinning” electron is also 2.0023. Similar ESR signals have been reported by Rupert (1973) for several arene-Cu(II)~montmorillonite complexes but only where a type II complex had formed. Rupert proposes that the d9 Cu(II) ion functions as an electron acceptor for the transfer of afiT—electron from the arene to form a radical cation which 39 then gives the ESR signal. Rupert attributes the lack of any hyperfine splitting to rapid electron exchange between radical cations and between radical cations and neutral diamagnetic species on the clay surface, result— ing in the single exchange narrowed ESR signal.‘ The fact that the type I phenol-Cu(II)-hectorite complex, where a complete electron transfer between the arene and the Cu(II) ion has not occurred, also exhibits this ESR signal indicates that Rupert's explanation is not completely satisfactory and that more research is needed in this problem. Ultraviolet-Visible Spectra. Figure 4B shows the ultraviolet-visible spectrum of phenol crystals dissolved in distilled water. It shows peaks at 273 mu and 278 mu. The ultraviolet-visible spectrum of the type I phenol-Cu(II)-hectorite complex is shown in Figure 4A. As can be seen, a single peak occurs at 475 mu accompanied by a broad region of absorption below 400 mu. The shift towards the visible region and the absorption broadening upon complexation are indications of a charge transfer process, in agreement with the complex conclusions from the infrared study of the phenol- Cu(II)-hectorite complex. Infrared: Co(II)-I Ni(II)-, Fe(III)-, A13+-. Mg2+-, Na+-, Li+-Hectorite. The sorption of phenol by each of the above kinds of 40 500 GAUSS _H_) g ,= 2.08 q = 2.0023 Figure 3: ESR spectra of freeze dried Cu(II)-hectorite over (A) no treatments: and (B) phenol and P205. .uopas uoHHapmHu Ga po>HommHu Hosonn Amv can .mzdu oa non nomm can Hocong op pomonxo can xmfiu sandSU a so novamomop ouanopoozufiHHvso Aupoaoa>¢hpas .3 ouswam .41 com 2.. .152“: was So ooe oo_r . q d u t u u d o d 02. _ cow Son 03” own can 03 emu owu d 42 O homoionic hectorite was studied, and no evidence of a‘Tr complex was noted in any of the systems. Table 3 summarizes the results for the most important diagnostic bands. Each of the homoionic systems retained a varying amount of coordinated water, depending on the hydration properties of the cation, even after the adsorption of phenol over P205. The DH deformation vibration is shifted 15-30 cm"1 to lower energy which suggests some weak hydrogen bonding_ of the hydroxyl group, particularly in the Co(II), Ni(II), and Fe(III) systems. The water bridging mechanism of Diagram 2 would seem to be the most likely interaction. The 5-10 or”1 shift in the” C-C stretching (Q 19a) vibration also suggests some weak‘flielectron interaction with the silicate structure. Infrared: NHL-. (CHBIBNH+-, (CH3)”N+-Montmorillonite. Ammonium and substituted ammonium montmorillonites (Upton, Wyoming) were exposed to phenol and P205. Table 4 summarizes the important infrared diagnostic bands. Ammonium ions would be expected to hydrogen bond to phenol and the OH deformation band, although partially obscured by the clay mineral absorption, occurs at 1210 cm"1 in. the phenol-NH:-montmorillonite complex. This is 20 cm"1 lower than in the highly associated solid phenol. As seen in Table 4, the infrared spectra of phenol adsorbed on trimethyl- and tetramethyl-ammonium montmor- 1 illonite shows a 13-14 cm- high energy shift in the CH 43 moss asap corp mesa soap cone corp pomp capo, as ropoaen -oosp maps camp ommp mmma oemp mmma send mama camp sac, aopoe inane mo\3 nopoupm mapm mama camp ooma mama reap amps amps ommp -- soap -ooma -esaoaoe so one emu mma emu mma mma mma emu Boa.»\ ocean upoupso mo +pq +oz +~m2 +mp< AHHHVoa AHvaz AHHVoo -wmm .oz coppeopp> spasm .wcpmmmwmp pampmcoo some: use: oco pom oooa op popdo: Comp can mason am new momm can Hoconm op pomomxo oppuopooz opcoono: mo Aaisov mpcmn consume“ popooaom .m manna 44 mosp Hosp noes pomp has”, as coaches scam Hmmp smmp ommH camp spar nopoeasco mo cap: ropoapo mesa mama ommp camp omma .. coppcsaoeoo mo mma ems oma ems cop.he ocean -eoipso mo +zsanmov +mzmamrov +smz accora .oz soapsanp> oppom .momm was Hosonm op enamonxo mason 3N popms oppcoaapuoe :pcoe so weeppmo BeacoEEd connp mo AH 80v mason topmMMCp popooaom .3 canoe 45 out-of—plane vibration and an 8—10 cm"1 low energy shift in the 0-0 stretching vibration. These shifts are inter- mediate between those of the ligand phenol on Cu(II)- and Ag(I)-hectorite, and those of phenol physically bound on the other homoionic hectorite systems reported in this study. This evidence suggests that, while no charge transfer type‘n’complex is formed, there is a significant ion-dipole interaction between the substituted ammonium cation and the phenol molecule. The 0H deformation vibration, as seen in Table 4, is less affected by the adsorption on the substituted ammonium systems than it is in the inorganic homoionic systems studied (Table 3). However, the 10-15 cm"1 low energy shift of the OH deformation band upon adsorption does suggest that hydrogen bonding mechanisms are Operating in the physical adsorption of phenol on the substituted ammo- nium montmorillonite. AROMNTIC ETHER STUDY Adsorption of Anisole on Cu(II)-Hectorite. The infrared spectrum of liquid anisole is shown in Figure 5A. A thin Cu(II)-hectorite film possesses the 2*, and its pale blue color characteristic of hydrated Cu spectrum is shown in Figure SB. When a Cu(II)+hectorite film is placed over anisole vapors (Figure 5C), with no external dehydrating treatments, it shows no apparent color change. The absorption bands in Figure 5C corre- spond closely to infrared bands of liquid anisole (Figure 5A), indication that this form of adsorbed anisole is physically bound to the clay mineral structure. Anisole is unable to favorably compete directly with water for ligand positions on the cation. When a Cu(II)-hectorite film is placed over anisole vapors and P205 dessicant, it turns a deep blue color (Figure 5E). If the filmis then exposed to atmospheric moisture for a few seconds, the deep blue color disappears and the film becomes tan in color (Figure 5D). The tan anisole complex, Figure 5D, appears to be a type I analog. There is no indication of the broad, intense 1 adsorption above 1800 cm- as in the type II spectrum of benzene (Doner and Mortland, 1969) but the CH out-of—plane 46 47 Figure 5: Infrared spectra of (A) liquid anisole: (B) an air dry Cu(II)-hectorite film: (C) hysically bound anisole on Cu(II)-hectorite: (D type I (tan) anisole complex on Cu(II)-hectorite: (E) type II (blue) anisole com lex on Cu(II)Ahectorite: and (P) type II ( reen 4,4'-dimethoxybiphenyl com- plex on Cu(III-hectorite. 48 l vibration is shifted up 23 cm' to 781 cm’1 compared to liquid anisole. The 4016 0-0 stretching vibration has 1 1 been shifted down 11 cm‘ to 1587 cm' appears at 1262 cm-1. This latter band likely arises from 1 , and a new band a 13 cm- high energy shift of the C-O-CH3 stretching mode upon formation of a type I complex. The blue anisole complex, Figure SE, is obviously a type II analog. The very intense absorption above 1800 cm"1 corresponds directly with that of the type II benzene com- plex, which Mortland and Pinnavaia.(l97l) attribute to a low energy electron transition arising from the dJTrCu(II)- benzene interaction. The CH out-of—plane region of liquid anisole, Figure 5A, shows a band at 758 cm'l. In Figure SE 1 we find a band at 760 cm" corresponding to physically 1 which is attri- 1 sorbed anisole, a strong band at 780 cm- buted to a type I complex, and a band at 812 cm- which is attributed to the f7’4b CH out-of-plane vibration character- istic of the type II anisole complex. This represents about a 60 cm'1 high energy shift of the CH out-of—plane mode upon type II complexation. The C-C stretching region of liquid anisole shows several clearly defined bands and shoulders. Formation of the type II complex produces shifts in the energies of these bands which overlap with absorption bands of the other two forms of adsorbed anisole present, creating the broad absorption region found between 1 1 1400 cm‘ and 1600 cm' . 49 Three forms of adsorbed anisole then may be identified on Cu(II)-hectorite, namely, physically sorbed, type I (tan), and type II (blue). Table 5 contains the assign- ments of the infrared bands for these three forms of adsorbed anisole. If a tan type I complexed film is not put in the infrared cell but mounted directly in the infrared beam, it will shortly turn green and exhibit the type II anisole spectrum. The heat of the infrared beam is evidently enough to partially dehydrate the film and convert the type I to the type II anisole complex. A similar effect was noted with the biphenyl-Cu(II)-montmorillonite complex (J. P. Rupert, 1973). If the film is removed from the infrared beam it turns tan once again. - Pleochroic studies on the type II anisole complex show no changes in intensity of any of the in-plane or out— of-plane vibrational modes, which indicates that the anisole is lying in the interlamellar regions with the plane of its ring at or near an angle of 450 to the clay plates. Stoichiometric studies on the type II system, which also contains physically sorbed and type I anisole, indi- cated that a total of about five molecules of anisole are 2+ u adsorbed on the hectorite per exchangeable 0 ion. Identification of the Green Type II Complex. When the blue, type II anisole-Cu(II)-hectorite com- plex is placed out in the air it adsorbs atmospheric 50 Table 5: Assi nments of selected vibrational frequencies (cm‘ ) of anisole as a liquid, as a physically bound species on all kinds of homoionic hector- iite studied, as a type I ligand on Cu(II)-hec- torite, and as a type II ligand on Cu(II)-hec- torite. Physically Type I T e II Liguid* Bound Cu(II) Quill) No.* Assignment* 690 696 - 699 \)8 of 0-0 752 760 781 812 \)4 7 C-H 783 785 - - 02 Q 0-0-0H3 825 - 827 835 \) 11 ’fC-H 880 885 885 890 ‘011' ‘UPC-H 1180 1178 1182 1180 - methyl bending ? 1247 1244 1262 1265 912 0 0-0-0H3 1292 1297 1294 1280 \i 3 .8 C-H 1304 1305 1313 1312 - methyl bending 1332 - 1335 1333 \) 9 t C-C 1442 1445 1442 1440 - ? 1454 14 54 14 54 H x) 13' \) 0-0 1469 1470 1470 ** - methyl bending 1499 1498 1487 H \) 13 x) 0-0 1588 - - N 0 16' \) 0-0 1599 1598 1587 1589 x316 \) c-c * Assignments taken from Green (1961) and Stephenson, Coburn and Wilcox (1961). it *Broad overlapping of bands makes assignment difficult. 51 moisture and reverts to the tan type I complex. If this type I complex is left out in the air overnight it turns to a green color. The infrared spectrum of this green complex is shown in Figure 5F. It is characterized by an 1 813 cm- CH out-of—plane vibration and an intense absorp- tion above 1700 cm'l. It is obviously a type II analog, but one that forms out in the atmosphere with no external dehydration treatments. _The spectrum resembles the parent anisole in many respects, but the complex is stable when immersed in distilled water. The fact that the green color forms only after the type II anisole complex is placed out in the air suggests that the reaction pathway is through either the type I complex or the physically bound anisole. Its formation is evidently promoted by one or more of three factors, namely: light, atmospheric moisture or oxygen. Light was eliminated as a factor when the green complex was found to form on films treated in the dark. When a film was complexed with anisole and placedain a vacuum cell over pure oxygen, the blue type II color remained stable and no green complex was formed. Oxygen alone, therefore, cannot be the critical factor. The presence of water must be important. It is known that the acidity at a clay surface is greater than that measured in a bulk solution (Mortland and Raman, 1968). It was felt that perhaps we were witnessing a surface acidity effect, where as atmospheric moisture was readsorbed and the type I 52 anisole complex and physically bound anisole became pre- dominate, the acidity at the clay surface initiated a reaction leading to the type II green complex. To test this hypothesis a blue, type II anisole complexed film was placed over the vapors of concentrated HCl for a few seconds. The film very rapidly turned dark green, and the infrared spectrum corresponded to that in Figure 5F, confirming the hypothesis that the reaction is acid catalyzed and that clay surface acidity is a controlling factor in the formation of the green complex. It was found that the green complex could be extracted with methanol in a few hours. The methanol could be dis- tilled off, and a highly crystalline product of light brownish color remained. The product had a melting point of 176°C, and the mass spectral analySis indicated a molecular weight in excess of 207. The infrared spectrum of the compound is shown in Figure 6. The anisole has undergone a dimerization reaction to form 4,4'-dimethoxy- biphenyl (m.w. 214, m.p. 173°) which then forms a type II complex with the Cu2+-hect0rite. Figure 6 corresponds exactly with the infrared spectrum of the authentic com- pound. The nmr spectrum of the isolated product also corresponds to that of the authentic compound. The follow- ing mechanism, similar to the one proposed by Kovacic and Kyriakis (1963) for the formation of p-polyphenyl in solution, is suggested: 53 .xoanaoo oppquoon: no poaupxo Hosunpoa soup coaappupu maupmhuo no «upon 7.5 .2383 u><3 . .s. - 8... a ‘ HHvso .HH snap .Cooum _ m possumcH poaaon any .w ouswpm ‘ ‘ ‘ ‘ ‘ N ‘ ‘ 1 ‘ ‘ 4 .om.t.&r..n? .o®_ TEu fieyetiuflfii p a? (1 d ’ p y ’ h ’ ’ D b . i. NOISSIHSNVUA S 54 55 In the presence of oxygen and in a hydrated condition on the clay surface, it is likely that Cu(I) will be rapidly oxidized back to the Cu(II) state. To test this hypothesis a blue, type II anisole complexed film was placed in a flask over nitrogen gas and a drop of water. No oxygen was allowed in the system. As the clay rehydrated, the blue complex disappeared and the film became tan in color. After twenty-four hours the film was still light tan, indicating that no green complex had formed in the absence of oxygen. When the film was taken out of the flask and placed in the air it turned green within a few minutes. These results suggest that the dimerization reaction had occurred on the Cu(II)-hectorite film under a nitrogen atmosphere but that the green, type II complex could not form because step # of the proposed mechanism had left capper in the +1 oxidation state. Type II com- plexation requires copper in the +2 oxidation state. When the film was placed out in the air. the Cu(I) was rapidly oxidized to Cu(II) and the green complex could then form. Ultraviolet-Visible Spectra. The ultraviolet-visible spectra of the deeply colored anisole and 4,4'-dimethoxybiphenyl complexes are shown in. Figure 7. Liquid anisole, Figure 7A, absorbs at 265, 271, and 278 mu. The blue anisole-Cu(II)-hectorite complex, Figure 7B, however, shows a strong band at 612 mu and a broad region of absorption below 360 mu. This intense .xoanaoo opauopoonuAHHvsouHhConanhxonposwon.:.: HH oak» .Coouw ADV new .AocHH oocmuov xoamsoo opwnopoontAHHvsonoHomasu HH oak» .osan Amv 56 .nopuz ooaaavmwu ca oo>HommHo onomwaa Aupoaow>mppas .m ouzmfim as .Eozmdzi o com 02. com can own cum con. - omu com cow \\\\1 o. \mafimou Lo _ 8 x 8 on on mm an i ow oe M H V W on on w M W l om cm 9 m m M E. 2. N om om om . om 8: . oo. 57 ultraviolet absorption, the shift into the visible region and the broad absorption: above 1700 cm“1 in the infrared region (Figure 5E) all agree with the previous work of V Pinnavaia and Mortland (1972) on the benzene-Cu(II)-mont- morillonite complex and are further evidence for a charge transfer type interaction between the’nLelectrons of the arene and the exchangeable Cu(II) ions. The spectrum of the green type II complex is shown in Figure 70. As can be seen, the spectrum is much different from that of the anisole complex, Figure 7B. This is further evidence that a reaction has taken place, and the green complex no longer contains anisole. The broad ultraviolet absorption, the two bands in the visible region and the infrared spectra, Figure 5F, are all analogous to the anisole system, however, and suggest that the #,h'-dimethoxybiphenyl complexis similar in nature to the other type II arene-Cu(II)-smectite complexes reported to date. Adsorption of Anisole on Other Kings of Homoionic Hectorite. The adsorption of anisole on other kinds of homoionic hectorite was also studied. Figure 8 shows representative spectra from this study. As can be seen in Figure 8A, the Ag(I)-hectorite forms a type I complex with anisole. The- CH out-of—plane band at 780 cm‘l, the C-O-CH 1 mode at 1262 cm'1 1 3 and the C-0 stretches at 1487 cm' and 1587 cm- all corre- spond to the type I Cu(II)~anisole complex bands in Figure 5D. As was noted in previous studies on Ag(I)-hectorite-arene 58 complexes (Clementz and Mortland, 1972 and Fenn and Mortland, 1972), no physically bound arene is adsorbed on the Ag(I)- hectorite. Twice as many Ag(I) ions are needed to satisfy the hectorite exchange capacity than Cu(II) ions. The formation of the type I complex by anisole molecules on Ag(I)-hectorite effectively covers the interlamellar surface area and blocks the physical adsorption sites on the silicate structure. As shown in Figures 8B and 8C, both Na+-hectorite and Co(II)-hectorite adsorb anisole by physical means only. The adsorption process appears to be independent of the exchange- able cation since similar spectra were obtained for all the kinds of homoionic hectorite studied where physically sorbed anisole was present. The band at 1696 cm"1 in Figures 5E and 8C, however, appears only in the transition metal saturated hectorite but not in the alkali metal or alkaline earth saturated hectorite studied. It is possible that this band is masked by the H 0 deformation band of residual 2 water on the alkali metal or alkaline earth homoionic hectorite. The band is in the C~O stretching region, but the other bands show no indication of any ketone or quinone formation from anisole. The origin of this weak band cannot yet be eXplained and requires further study. Adsorption of Other Aromatic Ethers on Homoionic Hectorite. The critical influence of the strong inductive effect of the methoxy group on the coordination of anisole with 59 Agni r r. .momm can opauo oozuhHHvoo ao>o oaomacu on can .mom& can opaaopoonu+mz uo>o oaomwcd Amv . omm can opfiaopoonuAva< uo>o odomaco A43 184243...e.féf§.e.fse.sxqse 32.3342... 8.! u. I. a v N S u" w m N 91 a“ _ . 3.! 3.2 O < a 4 up 8. axiom-pom. omo.»&:.&~..8.2f&zp&st&2.85..8w._&...8w~t8w~L88 83 Sat; 7.5 .9595: m><3 60 exchangeable Cu2+ is evident. No other substituted benzenes studied to date have been capable of forming a type II complex with the Cu(II)-smectites except where the substi- tution was with other benzene rings such as in biphenyl, naphthalene or anthracene (J. P. Rupert, 1973). Butyl phenyl ether, benzyl methyl ether and phenyl ether were also studied in order to further investigate We the effects of the ether linkage on the formation of the type II complex with Cu(II)-hectorite. Figure 9 shows the spectra obtained in the study of butyl phenyl ether. As can be seen in comparing the spectrum of liquid L; butyl phenyl ether (Figure 9A) with that of butyl phenyl ether adsorbed on Ni(II)-hectorite (Figure 93), only phys- ically bound ether is present. The CH out-of-plane vibration 1, ‘ and the Q 19a 1 is shifted up 8 cm'1 from 755 to 763 cm- 1 to C-C stretch is shifted down 6 cm' from lh98 cm- 1492 cm"1 compared to liquid butyl phenyl ether. These small shifts indicate that the adsorption process may involve a weak'fltelectron interaction between the silicate surface and the butyl phenyl ether. The positions of the above peaks are independent of the exchangeable cation. The C-O-R~gstretching vibration at 1248 cm‘1 in liquid butyl phenyl ether does show some cation dependence, however. With butyl phenyl ether adsorbed on Ni(II)-hectorite (Fig- ure 9B), the C-O—R stretch occurs at i233 cm“1 1 3 while on A13+-hectorite it occurs at 1217 cm‘ , and on Ns+-hectorite 61 The band is at 12hu~cm'l. These results suggest that the physical adsorption process may involve either (A) hydro- gen bonding to coordinated water on the cation; or (B) direct coordination between the cation and an unshared pair of electrons on the ether linkage, depending on the cation. These two processes are shown below: (A) MEt-oo nogpo Andean szsn on .mo m can opauopoosuAHHsz uo>o nonvo Hhconn Hanan Amv .aospo Hanosn Hausa oasdda A4 }.m 9 . J: a a .a.. la» 3o. . a s a . o. . . .u“ .. . a . \ .... .. 3.. .. a 1 a s . e a a a _ . . . ..u \\\at R . Obs c . . s . n . . a . s\ o ... .... .. l . i .1 . eh. .... 1. . :3 . s, .“ ... ._ “ ... “7:-.. . .. r. .. . .. . .. a. so « p\ .1 , xx C . a ..C w x . \\ . \\ o . .3. ./. 8... . ... ........... 2 8: . \L 3: a. .s I . \\\ o l .. .. to ..... u/ .k 8 ... u /o{\\ \\\\\\ Inc! 0 v .2 ... ... m x. a... .. .. M a . o \c a .. . «w w up n \Iolxl ll .. .. M. a: , a... ... m .. n1 ... , ... 8.: 5.. 2n .. u a .3 s. » \\— o \ “ raw \x y N w w 362 o ”m l ‘1 s I o a. w\\ ,2m m m m x L.\ l 0. c a o - o - no a < . . . o; .. < .. Er. .. I x a .. a . 1/ \\ '0‘)’ 0‘ o o: W! I \|I\\\\\ .8. r a \ / ollIt‘ llolIOII la! \\ '0‘ “5'. lllII|\ 8.“ v. 32 J. a: an. 2... . . mo». 01 no.9 ( 3a.. < ( 8..&a.a.x.&.r&2.&:.&2+&2.&zr&2.a...&:.&...&:..i .i. 7.5 .2395: m><3 61 high energy shift of the \312 C-O-R stretching vibration which occurs at 12h8 cm"1 in liquid butyl phenyl ether. 1 The ‘088 c-c stretch has shifted down from 1600 cm' to 1565 cm"1 in the type II complex. A comparison of Figure 9D with Figure 9B in the region above 2#00 cm"1 shows additional evidence for the type II butyl phenyl ether complex on Cu(II)-hectorite. The broad absorption . {3 remains intense out to #000 cm"1 in the spectrum of 5 Figure 9D where the type II complex is present but not in Figure 93 where only physically bound butyl phenyl ' ether is present. &! Phenyl ether and benzyl methyl ether did not form type II complexes with Cu(II)-hectorite. In the benzyl methyl ether system, a methylene group is situated between the ring and the methoxy group. This CH2 group prevents the unshared pairs of electrons on the ether oxygen from participating in resonance with the’fizelectrons of the benzene ring. In phenyl ether there is no shielding methylene groups but both rings compete for resonance with the linking oxygen. Resonance between the ring and the ether oxygen, therefore, appears to be critical in the formation of the type II complex by anisole and butyl phenyl ether on Cu(II)-hectorite. Benzyl methyl ether did form a type I complex with Cu(II)-hectorite as evidenced by shifts in the CH out-of—plane and C-0 stretching vibrations upon complexation which were comparable to shifts in previously studied type I complexes. With phenyl 69 ether, the thin Cu(II)-hectorite film turned a light green color indicating complexation, possibly a type I analog, had occurred. This complex was extremely unstable, how- ever, and good infrared spectra could not be obtained. ESR data on phenyl ether with freeze dried Cu(II)-hectorite is discussed next in this paper and further indicates a complex is formed between Cu(II)-hectorite and phenyl ether. Electron Spin Resonance: Aromatic Ethers Adsorbed on Cu(II)- Hectorite. The ESR spectra of the adsorbed ethers are shown in Figure 10, and the respective g values are listed with each figure. As can be seen the values are all very close to the g value of 2.0023 for a "free spinning“ electron, although the last digit in the g values of Figures 10B--10F is not highly significant. There is no evidence of any hyperfine splitting of the narrow band. The phenyl ether and benzyl methyl ether strongly show the presence of Cu2+ spins. These systems are obviously interstratified, and the complex has not maximized on all the available ligand 2+ signals are noted in the butyl phenyl sites. Weaker Cu ether and the #,4'-dimethoxybiphenyl complexes also. In addition to the "free" electron signal in the ESR spectra of the type I complexes of benzyl methyl ether and phenyl ether, a sharp peak of similar g value has been observed in the ESR spectra of the type I Cu(II)-hectorite complexes of toluene (Cady, personal communication) and phenol. It is 65 clear, therefore, that this narrow ESR signal is not a singular property of the type II complex since several type I complexes on Cu(II)-hectorite also exhibit the signal. Rupert (1973) proposes that the d9 Cu(II) ion functions as an electron acceptor for the transfer of a ’fitelectron from the arene to form a radical cation which then gives the ESR signal. The lack of hyperfine splitting in the spectrum is attributed to rapid electron exchange between radical cations or between radical and neutral, diamagnetic species resulting in the single, exchange- narrowed ESR band. Rupert, however, only observed signals on type II Cu(II)-montmorillonite-arene complexes. The fact that the signal is also found in 0u(II)-hectorite systems containing only type I complexes but not in the type I Ag(I)-hectorite complexes (D. M. Clementz, unpub- lished data) suggests the need for further research on this "free” electron signal in arene-Cu(II)-smectite complexes. 66 .AonnEoo sooumv momm one noses Hanozn Amv use “AonQEoo czoanv momm was nospo flagpoe Hanson Amy .AonnEoo manusmv momm can soaps Hmcogn Hhvsn any .onmEoo Ahsosnwnhxonpoaaou.:.: .sooaw on .AonnEoo osanv momm one oaomwcs Amv .mvcospdoup o: Ao onwaovoosuAHHvso soaps snoopy mo mapoonm mmm C§.Nu. T )U o seesaw T owned-o u I 8.Na4. a 88“.. . . g) < . .38 08 Tz| .3 enemas SUMMARY AND CONCLUSIONS 1. Cu(II)-hectorite forms a type I‘flicomplex with phenol in the presence of P205 dessicant. The complex is distinguished by a 32 cm"1 high energy shift in the quob CH out-of-plane vibration and a 17 cm'1 low energy shift in the \Ql9a C-C stretching vibration. The complex is black in color. Physically bound phenol is present simul- taneously with the complex on Cu(II)-hectorite. 2. Ag(I)-hectorite forms a type I‘fiicomplex with phenol. The complex is distinguished by a 29 cm"1 high energy shift in the 7’10b CH out-of-plane vibration and a 17 cm"1 low energy shift in the “019a C-C stretching vibra- tion. No physically bound phenol is formed on the Ag(I)- hectorite. 3. Stoichiometric studies indicate that about five 2+ ion. molecules of phenol are adsorbed per exchangeable Cu This total includes ligand phenol and physically bound phenol. 0n Ag(I)-hectorite about one molecule of phenol was adsorbed per exchangeable Ag+ ion. Pleochroic studies indicate that the phenol molecule is oriented in the inter- lamellar region on an angle more toward the vertical than the horizontal. 67 68 a. The ESR spectrum of the phenol-Cu(II)-hectorite complex shows a single, sharp signal at a g value of 2.0023. 5. Co(II)-, Ni(II)-, Fe(III)-, A13+-, mg2+-, Na+-, and Li+-hectorite all adsorb phenol by physical processes only. No ligand phenol was formed on any of the above homoionic hectorites. Suggested adsorption mechanisms include hydrogen bonding to oxygen of the silicate structure, hydrogen bonding through a water bridge to the exchange- able cation, and weak‘nielectron interaction with the silicate structure. 6. Trimethyl ammonium- and tetramethylammonium- montmorillonite adsorb phenol by an ion-dipole interaction between the substituted ammonium cation and the phenol molecule. Hydrogen bonding and a weaquLelectron inter- action with the silicate structure are also probably occurring. 7. Three forms of adsorbed anisole are present on Cu(II)-hectorite over P205 dessicant, namely: physically bound anisole, a type I complex (tan) and a type II complex (blue). The type I complex is characterized by a 29 cm-1 high energy shift in the \M CH out-of—plane vibration, a 12 cm"1 low energy shift in the ‘013 C-C stretching mode and a 15 cm”1 high energy shift in the‘QlZ C-O-CH3 vibra- tion. The type II complex is characterized by a 60 cm"1 high energy shift in the ‘04 CH out-of-plane Vibration and an intense absorption above 1700 cm“l which obscures the rest of the spectrum. 69 8. When a type II anisole complexed film is placed out in the air, the blue color rapidly disappears and the film becomes tan in color. After several hours in the air the film will turn green and exhibit a type II spectrum. A dimerization reaction has occurred to form h,h'-dimethoxy- biphenyl from anisole and the product then forms the type II complex with Cu(II)-hectorite in the presence of oxygen. Ft 9. The dimerization reaction proceeds through the type I anisole complex and/or physically bound anisole and is catalyzed by acidity at the clay surface. Oxygen is nec- §_ essary to oxidize Cu(I) back to Cu(II) before type II green ij complex will form after the dimerization reaction has occurred. 10. Butyl phenyl ether forms a type II complex on Cu(II)-hectorite over P205 dessicant, and forms a type I complex on Ag(I)—hectorite. ll. Benzyl methyl ether and phenyl ether formed type I complexes with Cu(II)-hectorite but not type II complexes. This points out the importance of the special inductive effect of the —OR group on the activity of the phenyl ring. Anisole and butyl phenyl ether are the first known substi- tuted benzenes to form the type II complex. 12. The ESR spectra of each of the Cu(II)-hectorite- arene complexes studied showed a single, sharp signal near a g value of 2.002. This was true of both the type II and type I complexes. LITERATURE CITED Abramov, V. N., A. V. 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