Absorption and magnetic circular dichroism spectra of Ru⁴⁺ in Cs₂ZrCl₆ and Cs₂SnBr₆

Abstract

High resolution absorption and magnetic circular dichroism (M.C.D.) spectra are reported for Ru⁴⁺ (4d⁴) in the cubic hosts Cs₂ZrCl₆ and Cs₂SnBr₆. The spectra were recorded at liquid helium temperature over the ranges 16 000–26 000 cm^-1 and 11 000–22 000 cm^-1 respectively. All of the major features can be interpreted in terms of ligand-to-metal charge-transfer transitions. The results illustrate the need to use intermediate coupling in the 4d⁴ ground state, and a detailed analysis of the charge-transfer bands yields considerable information on the spin-orbit splittings of the ligand MO's and on the magnitude of metal-ligand electrostatic splittings. Excited state spin-orbit coupling is found to be much more important than metalligand electrostatic interactions. Comparisons are made with previous work on OsCl₆ ^2- and OsBr₆ ^2- (5d⁴).