|Budget Amount *help
¥2,000,000 (Direct Cost : ¥2,000,000)
Fiscal Year 1995 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1994 : ¥1,500,000 (Direct Cost : ¥1,500,000)
Phosphorescence energy transfer within ligand bridged diruthenium (II) compounds of the form (bpy)_2 Ru (II) (L-SP-L) Ru (II) (decbpy)_2^<4+>, where bpy, decbpy, and L are 2,2'-bipyridine, 4,4'-di (ethoxylcarbonyl) -2,2'-bipyridine, and 2- (2'-pyridyl) benzimidazoyl, respectively, and SP is either p-xylenyl groupe or a polymethylene chain (- (CH_2)_n-, n=2-6 and 10), was investigated in butyronitrile solution in the temperature range 77-330K.Excitation energy transfer occurs from the Ru (bpy)_2^<2+> moiety to the Ru (decbpy)_2^<2+> moiety. The energy transfer rate (k_<EN>= (0.4-7.4)x10^6s^<-1>) at 77K is weakly dependent on the Ru^<2+>-Ru^<2+> distance (gamma), which is estimated for the extended conformer of the polymethylene chain. A linear plot of log k_<EN> vs. log 1/gamma^6 shows that energy transfer occurs via the dipole-dipole interaction. The weak temperature-dependence of the energy transfer rate in the temperature range 77-110K is explained in terms of the absorption-emission coupling integral. The fast rnergy transfer (55x10^6s^<-1>) within (bpy)_2 Ru (bpbimH_2) Ru (decbpy)_2^<4+> (bpbimH_2=2,2'-bis (2-pyridyl) bibenzimidazole) at 77K is ascribed to the substantial exchange interaction between the Ru (bpy)_2 (bpbimH_2)^<2+> moiety in the excited state and the Ru (decbpy)_2^<2+> moiety in the ground state.