W. Humbs et al., LOWEST EXCITED TRIPLET-STATES IN [RU(BPY)(3)](2- A COMPARATIVE-STUDY BASED ON HIGHLY RESOLVED SPECTRA() AND [RH(BPY)(3)](3+) ), Journal of luminescence, 72-4, 1997, pp. 677-678
The lowest excited states of [Ru(bpy)(3)](2+) (bpy: 2,2'-bipyridine) e
xhibit a very strong involvement of metal 4d orbitals, while the metal
character is extremely small in the states of [Rh(bpy)(3)](3+). This
contrasting behavior is clearly displayed in the emission and excitati
on spectra, when ligands are isotopically marked. It is demonstrated t
hat these states, being of metal-to-ligand charge transfer character (
(MLCT)-M-3) in Ru(II) compounds, are covalentely delocalized over the
metal and the different ligands, while the ground and the lowest excit
ed states of Rh(III) compounds being of (3) pi pi character are cente
red on individual ligands.