Magnetic circular dichroism spectra of cobalt(III) amine complexes of photochemical importance

Magnetic circular dichroism spectra of several acidoamine cobalt(III) complexes are reported which reveal B terms for the spin allowed bands and A terms for the spin forbidden bands. It is shown that ligand field parameters derived from fitting of a full set of spin forbidden bands, including the quintet, gives Racah B and C electron repulsion parameters closer to those anticipated from theory than has been common using mainly the singlets and a single weak low energy absorption feature assigned to a triplet. The spectra indicate that the quintet which has figured in numerous photochemical speculations lies at relatively high energy. This conclusion is a consequence of both the recognition of an A term assignable to the quintet and the best fit ligand field parameters for all bands.