The solution electronic absorption spectra of low-symmetry mixed ligand complexes—III. Bromochlorotetrakis(pyridine)nickel(II) in chloroform

Abstract

Abstract Bromochlorotetrakis(pyridine)nickel(II) has been prepared and characterized by means of elemental analysis, infrared spectra, conductance measurements and electronic spectra. The electronic spectrum in a 10% solution of pyridine in chloroform has been recorded at room temperature and then resolved into precise positioned bands by Gaussian analysis. From the obtained band positions the ligand field parameters and transition energies have been calculated. The resolved spectrum has been studied theoretically using a crystal field model (CFM) and an angular overlap model (AOM). The ligand field parameters have been calculated by two minimization algorithms: the Davidon—Fletcher—Powell method (gradient estimation) and the Powell method (non-gradient). The standard deviations of the parameters have been obtained from the former. The spectral AOM parameters, derived from the computer analysis are eσ(L) and eπ(L) of σ and π antibonding for the three different ligating atoms [L = N(py), Cl and Br] (allowing possible anisotropy of pyridine nitrogen).