Chapter 1 provides an overview of the properties and reactivity of the rare earth metals, as well as single-molecule magnetism. The importance of the lanthanide ions to the design of single molecule magnets is also described. Several design criteria are introduced relating to the reduction of harmful through-barrier relaxation pathways of single-molecule magnets, including: the development of appropriate ligand scaffolds and the introduction of radical-containing ligands.Chapter 2 and Chapter 3 describe the isolation of unprecedented mono- and dinuclear rare earth metal complexes bearing 2,2’-azobispyridyl (abpy) anions. The mononuclear, Cptet2Y(abpy•), and dinuclear radical-bridged complex, [(Cptet2Y)2(μ–abpy•)](BPh4) (Cptet = tetramethylcyclopentadienyl) were characterized through crystallography, spectroscopy, and Density Functional Theory. The presence of a radical on the abpy ligand was confirmed both through EPR spectroscopy and computations. Chapter 4 describes the synthesis and characterization of three dinuclear rare earth complexes bearing bridging pyrrolyl anions, [(Cp*2RE)2(μ–1ƞ2–pyr–2κN)(μ–2ƞ2–pyr–1κN)], (RE = Y, La, and Dy; Cp* = pentamethylcyclopentadienyl, pyr = pyrrolyl). The steric bulk imposed by the pentamethylcyclopentadienyl anions results in a unique, asymmetric, bridging motif for both pyrrolyl ligands. Chapter 5 describes the first implementation of 2,3,4,5–tetraiodopyrrolyl as a ligand in coordination chemistry for any metal ion, in the form of three isostructural rare earth metal complexes, Cp*2RE(TIP) (RE = Y, Gd, and Dy). The impacts of the ligand on the physical properties of the metal were investigated computationally, spectroscopically and through SQUID magnetometry. In order to assess the impact of the I–atom in the first coordination sphere of the metal, an alkyl-substituted analog was additionally investigated, Cp*2RE(DMP) (RE = Y, and Dy; DMP = 2,5–dimethylpyrrolyl). Chapter 6 and Chapter 7 describe the synthesis and reactivity of dinuclear rare earth metal complexes comprising ancillary guanidinate ligands, [{(Me3Si)2NC(NiPr)2}2RE(μ–Cl)]2, (RE = Y, Gd, Tb, and Er). A bridge splitting reaction mechanism was investigated which is hitherto unknown in the realm of rare earth metal chemistry. Chapter 8 and Chapter 9 describes the synthesis and reactivity of rare earth guanidinate complexes bearing an inner sphere tetraphenylborate anion, [{(Me3Si)2NC(NiPr)2}2RE][(μ-η6-Ph)(BPh3)] (RE = Y, Dy). The steric bulk imposed by the guanidinate scaffold results in an asymmetric η6-bonding interaction between the metal and one phenyl ring of the tetraphenylborate anion. These molecules were used to produce hitherto unknown guanidinate rare earth metal complexes bearing radical anions. The first contains a 2,2'-bipyridyl radical anion, and the second bears a 2,2’-bisbenzimidazole bridging dianion which through chemical reduction affords only the second example of a 2,2’-bisbenzimidazole radical anion. Chapter 10 presents the capture of a planar benzene dianion in between two rare earth metal cations each stabilized by two guanidinate ligands. The synthesized inverse sandwich complexes [{(Me3Si)2NC(NiPr)2}2RE]2(μ–ƞ6:ƞ6–C6H6), (RE = Y, Dy, and Er) feature a remarkably planar benzene dianion, previously not observed for any metal besides uranium. The formal charge on the bridging benzene unit was confirmed through single-crystal X-ray diffraction, spectroscopy, and SQUID magnetometry. Nucleus-independent chemical shift calculations hint at an antiaromatic bridging unit, consistent with the presence of a benzene dianion. Chapter 11 describes the synthesis and characterization of a series of guanidinate and amidinate uranium complexes. The substitution pattern and electron donation ability of the ancillary ligand was evaluated on the basis of structure and electrochemical influence. Chapter 12 provides some additional experiments relating to guanidinate lanthanide complexes and their utility to isolate heterobimetallic systems, and guanidinate lanthanide complexes bearing 2,2’-azopyridyl bridging ligands. Chapter 13 serves as a summary for all aforementioned chapters.
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