COMPARATIVE-ANALYSIS OF THE ELECTRONIC AND EPR-SPECTRA OF COPPER(II) AND NICKEL(I) COMPLEXES - INSIGHTS INTO NICKEL(I) ELECTRONIC-STRUCTURE

The nickel(I) complex with the ligand 1,2-bis(pyridine-2-carboxamido)b enzene (H(2)bphen), generated by reduction with sodium amalgam of the homologous nickel(II) complex, has been studied by EPR and electronic spectroscopy. The electronic, structural and bonding properties of the complex were elucidated based on a comparison of the EPR and UV/VIS d ata of isoelectronic complexes of (CUII)-C-63 and Ni-61(I) Of H(2)bphe n. Analysis of the spectroscopic data revealed that the complex exhibi ts low covalency in the sigma in-plane bonding and high covalency in t he out-of-plane pi bonds, and has enabled the assignment of the electr onic bands at approximate to 13500 and 19600 cm(-1) of [Ni-I(bphen)](- ) to d(xz), d(yz) <-- d(xy) and d(x2-y2) <-- d(xy) transitions. Implic ations for the spectral characterization of cofactor F-430 systems are also presented.