Synthesis and characterization of imidazole and thioether ligands and their complexes as models for the type I and II copper proteins.

摘要

This dissertation is a structural and spectroscopic study of the monovalent and divalent pseudotetrahedral complexes of the ligands 2,2{dollar}spprime{dollar}-bis(2-imidazolyl)biphenyl (L), and 2,2{dollar}spprime{dollar}-bis (2-(4(5)-(2-(tert-butylthio)ethanethio))imidazolyl) biphenyl (N{dollar}sb2{dollar}S*{dollar}sb2{dollar}).; The bidentate ligand 2,2{dollar}spprime{dollar}-bis(2-imidazolyl)biphenyl (L) exhibits an unparalleled degree of geometric control for the tetrakis(imidazole) ligand set with Cu(II), Ni(II), Co(II), and Cu(I). Both Ni(II)N{dollar}sb4{dollar} and Cu(II)N{dollar}sb4{dollar} complexes, which normally undergo ligand field driven distortion toward planarity, have been effectively constrained in pseudotetrahedral, essentially D{dollar}sb{lcub}rm 2d{rcub}{dollar} point symmetry. Intraligand N{dollar}sb2{dollar}M/N{dollar}spprimesb2{dollar}M dihedral angles range from 86.4(2){dollar}sp{lcub}rm o{rcub}{dollar} to 89.3(2){dollar}sp{lcub}rm o{rcub}{dollar} for these four complexes. Geometric constraints within the nine-member chelate rings cause intraligand N-M-N angles to exceed the tetrahedral value of 109{dollar}sp{lcub}rm o{rcub}{dollar}, flattening the otherwise tetrahedral MN{dollar}sb4{dollar} units in the increasing order: Cu(I) {dollar}sim{dollar} Co(II) {dollar}<{dollar} Ni(II) {dollar}<{dollar} Cu(II). The synthesis, electronic absorption and electron spin resonance (ESR) spectra, magnetic and structural properties are discussed, as are electrochemical and NMR derived electron self-exchange measurements for the Cu(I)/Cu(II) pair. These latter chromophores are relevant models for the blue copper proteins or derivatized superoxide dismutase proteins with Cu(II) in the native Zn(II) site.; The tetradentate ligand 2,2{dollar}spprime{dollar}-bis (2-(4(5)-(2-(tert-butylthio)ethanethio))imidazolyl) biphenyl (N{dollar}sb2{dollar}S*{dollar}sb2{dollar}) also yields pseudotetrahedral N{dollar}sb2{dollar}S*{dollar}sb2{dollar} coordination geometries with Ag(I), and Cu(I). Attempts at complexation with Cu(II) gave 2:1 N{dollar}sb2{dollar}S*{dollar}sb2{dollar}:Cu(II) complexes with N{dollar}sb4{dollar} ligand sets presumably because of the low affinity of Cu(II) for thioether. The synthesis, structural studies, and electronic absorption and electron spin resonance (ESR) spectra of the Cu(II) N{dollar}sb4{dollar} complex are discussed. The Ag(I) and Cu(I) chromophores are relevant models for the reduced Cu sites of the blue copper proteins.; The synthesis of two potential ligands (2,2{dollar}spprime{dollar}-bis (2-(4(5)-(2-(mercapto)ethanethio))imidazolyl) biphenyl, N{dollar}sb2{dollar}S{dollar}sb2{dollar}, and {dollar}{lcub}{dollar}2- (2-(4(5)-(2-(mercapto) ethanethio))) imidazolyl, 2{dollar}spprime{dollar}- (2-(4(5)-(2-(tert-butylthio)ethanethio))) imidazolyl{dollar}{rcub}{dollar} biphenyl, N{dollar}sb2{dollar}SS*) as models for the blue copper proteins is also discussed.