ELECTRON DELOCALIZATION AND LOCALIZATION IN MIXED-LIGAND [RU(LL)(N)(LL')(3-N)](2+) COMPLEXES

Highly resolved emission spectra of isolated [Ru(LL)(n)(LL')(3-n)](2+) complexes doped into [Zn(bpy)(3)](ClO4)(2) with LL and LL' representing the ligands bpy-h(8), bpy-d(8), and bpz are presented. The information displayed in the electronic origins and the vibrational satellite structures combined with the emission decay behavior is used to provide a clear distinction between localized and delocalized MLCT transitions to the lowest excited states. In particular, the appearance or nonappearance of ligand-centered vibrational modes belonging to different types of ligands provides crucial evidence for delocalization or localization. Thus, for a localized excitation in [Ru(bpy)(2)(bpz)](2+) only the ligand-centered modes of bpz can be found in the emission spectra. In contrast, for [Ru(bpy-h(8))(2)(bpy-d(8))](2+) the ligand-centered vibrations of bpy-h(8) and bpy-d(8) accompany the same electronic origin. This is strong evidence for the delocalization of the excited electron in mixed-ligand [Ru(bpy-h(8))(2)(bpy-d(8))](2+). Consequently, the lowest MLCT excited states in homoleptic complexes like [Ru(bpy-h(8))(3)](2+)and [RU(bpy-d(8))(3)](2+) are also delocalized over the metal and the different ligands.