LOCALIZED (3)MLCT STATES OF [RU(BPY)(3-X)(PHEN)(X)](2+) (X=0 TO 3) IN RACEMIC [ZN(BPY)(3)](CLO4)(2)

Non-selective and line-narrowed excitation and luminescence spectra of the series [Ru(bpy)(3-x)(phen)(x)](2+) (x=0 to 3) doped into racemic [Zn(bpy)(3)] (ClO4)(2) are reported. The lowest-excited (3)MLCT level of the bpy ligand(s) is 125+/-5 cm(-1) higher in energy than the lowest-excited state of the phen ligand in the mixed complex with x=1. Fast energy transfer to the phen ligands deactivates the bpy excitation in the x=2 system. In the x=1 system a superposition of bpy and phen emission is observed. This superposition is a consequence of the crystallographic inequivalence of the bpy ligands in the host. Characteristic energy separations are observed for the three lowest-excited (3)MLCT states involving the bpy or the phen ligands. This indicates that the excitation exchange interaction between metal-ligand subunits is smaller than 0.5 cm(-1) for the series.