Characterization of exciplexes generated by excited tris-diimine-ruthenium(II) complexes and silver(I) ion of ground state

Luminescent bimolecular and termolecular exciplexes of *[Ru(bpy)(3)](2+) and *[Ru(phen)(3)](2+) (bpy =2,2'-bipyridine, phen = 1,10-phenanthroline) formed by silver ions have been characterized and compared. Formation constants, luminescence lifetime, radiative and nonradiative decay constants were determined at room temperature. Oxidative quenching measurements in the [Ru(bpy)(3)](2+)-Ag+ system using MV2+ (MV2+ = 1,1'-dimethyl-4,4'-bipyridinium) as an electron acceptor resulted in quenching rate constants, (3.1+/-0.2)x10(9), (3.1+/-0.3)x10(9), (1.6+/-0.3)x10(9) and cage escape efficiencies, 0.11+/-0.01, 0.05+/-0.01, 0.06+/-0.01, for *[Ru(bpy)(3)](2+), *[Ru(bpy)(3)lAg(3+) and *[Ru(bpy)(3)]Ag-2(4+), respectively. Temperature-dependent luminescence lifetime in aqueous solutions revealed that the exciplex formation causes a considerable change in the deactivation pathways of the excited species. Exciplex formation results in a decrease in the efficiency of the thermally activated decay through MLCT --> dd transition and in an increase of the efficiency of deactivation to the ground state via other non radiative processes. The thermodynamic parameters of the exciplex formation have been estimated. (C) 1998 Elsevier Science S.A.