Comparative analysis of the electronic and EPR spectra of copper(II) and nickel(I) complexes; insights into nickel(I) electronic structure
Abstract
The nickel(I) complex with the ligand 1,2-bis(pyridine-2-carboxamido)benzene (H2bphen), 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 data of isoelectronic complexes of 63CuII and 61NiI of H2bphen. Analysis of the spectroscopic data revealed that the complex exhibits low covalency in the σ in-plane bonding and high covalency in the out-of-plane π bonds, and has enabled the assignment of the electronic bands at ≈13 500 and 19 600 cm–1 of [NiI(bphen)]– to dxz, dyz ← dxy and dx2 – y2 ← dxy transitions. Implications for the spectral characterization of cofactor F430 systems are also presented.