Date of Award
Fall 2015
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Chemistry
First Advisor
Gardinier, James R.
Second Advisor
Rathore, Rajendra
Third Advisor
Yi, Chae S.
Abstract
Historically, the study of mixed valence complexes has been critical for advancing our understanding of electron transfer processes in biological and abiological systems. The recent use of mixed valence complexes in electrochromic materials, and the promise of their use in future technological or molecular electronic applications, has spurred further interest in this class of compound. Previous studies by our research group have shown that gallium(III) or tricarbonylrhenium(I) complexes of pincer-type ligands with diarylamido anchors and either pyrazol-1-yl (pz) or diarylphosphino (PAr2) flanking donors are electroactive species with quasi reversible ligand-centered oxidations. Moreover, the one-electron oxidized derivative with pz flankers, [Ga(L)(L+)]2+ was found by both spectroscopic and electrochemical means to be a Robin Day Class II species with weak electronic communication occurring between pincers across the main group metal bridge. Cursory electrochemical studies suggested that stronger interactions occurred on replacing gallium(III) with other metal centers. This dissertation elaborates on these initial, prior, findings by describing more detailed synthetic protocol to various [M(L)2]n+ complexes where M = Ni, Co, Rh, Ir, n = 0-3 (depending on M), and where L has different organic groups decorating the periphery. Electrochemical measurements and in-depth spectroscopic analyses of oxidized and reduced forms of the complexes were used to better quantify the effects of metal and ligand substitution on their electronic properties including the extent of electronic communication in mixed valence derivatives. Another goal of the work was to prepare in multimetallic pincer complexes via both covalent and self-assembly approaches and study their electronic properties. Thus, the preparation and properties of [Re(CO)3]2(-L-L) with dinucleating pincers (L-L) is described. Initial successes and difficulties with the preparation and characterization of coordination networks based on these pincers and those with different Lewis donors at the para- aryl position are outlined next. Finally, ‘Extended Pincers’ (EP), ligands comprised of an N,N’-diarylformamidinate anchor with flanking pz and/or PAr2 ortho-aryl donors were prepared since they should support multimetallic complexes with unusual metal-metal bonds or reactivity due to proximity of the metal centers. Their group 1 and group 11 metal complexes may serve as useful reagents for future chemistry.