Tetrahedral transition-metal complex spectra

Abstract
Low-temperature single-crystal absorption, emission and magnetic studies are reported on the tetrahedral complexes [(CH3)4N]2MnCl4 and [(CH3)4N]2MnBr4. All nine d-d bands predicted by crystal field theory are observed in the optical spectra, many with detailed fine structure. The general features of the spectra are analysed using the Tanabe-Sugano strong-field scheme, including the Tree's correction, with excellent results. The finer spectral details are accounted for by spin-orbit interaction via a complete 3d 5 crystal field-spin orbit calculation. The effects of tetragonal distortions are considered and shown to be small. Several ‘mystery’ bands are observed at low temperatures in thick crystals and discussed in terms of possible sextet-doublet transitions.