LOWEST EXCITED TRIPLET-STATES IN [RU(BPY)(3)](2- A COMPARATIVE-STUDY BASED ON HIGHLY RESOLVED SPECTRA() AND [RH(BPY)(3)](3+) )

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.