Resonance Raman spectroscopy of [RuCl₆]^2- and [RuBr₆]^2-

Abstract

Vibrational and electronic resonance Raman spectra of the 4d ⁴ complex ions [RuCl₆]^2- and [RuBr₆]^2- are reported for the first time and discussed in terms of established theories. The spectrum of each ion displays progressions in the v ₁(a _1g ) mode, together with subsidiary progressions involving the v ₂(e_g ) and v ₅(t _2g ) fundamentals. Higher wavenumber bands are assigned to transitions between the spin-orbit components of the ³ T _1g ground term. The excitation profiles of vibrational and electronic Raman bands of [RuCl₆]^2- have been measured in detail and are compared with the electronic absorption spectrum of the ion. The effect of temperature and counterion on the electronic Raman spectra is discussed. Polarization measurements for the v ₁ bands of the ions in solution strongly suggest that they have octahedral symmetry in the Γ₁(³ T _1g ground state.