Vibrational Sidelines in the Localized ³MLCT Emission of [Ru(bpy)₂(bpz)]²⁺ in [Zn(bpy)₃](ClO₄)₂ (bpy = 2,2‘-Bipyridine, bpz = 2,2‘-Bipyrazine)

Abstract

It is accepted that the transferred electron in the lowest-excited 3MLCT states of [Ru(bpy)2(bpz)]2+ is localized on the bpz ligand. We have investigated the luminescence spectrum of the complexes [Ru(bpy)2(bpz)]2+ and [Ru(bpy-d8)2(bpz)]2+ in the [Zn(bpy)3](ClO4)2 host with great precision, and we are able to unambiguously identify sidelines associated with the spectator bpy/bpy-d8 ligands over the entire vibrational frequency range. Thus, the mere presence or absence of high-frequency vibrational sidelines in 3MLCT emission cannot be used to argue for delocalization or localization of the transferred electron. Dominant sidelines reported previously by another group for [Ru(bpy)2(bpz)]2+ in [Zn(bpy)3](ClO4)2 are due to a contamination of the sample with the chromophore [Os(bpy)2(bpy-d8)]2+.