EMISSION-SPECTROSCOPY OF RU(BPY)(2)DPPZ(2- PROBING THE CHEMICAL ENVIRONMENT IN CAST FILMS() IN NAFION )

The incorporation of Ru(bpy)(2)dppz(2+) (dppz = dipyrido[3,2-a:2',3'-c ]phenazine) into Nafion coatings was monitored in situ by electronic a bsorption, steady-state emission, and lifetime measurements. Whereas t he aqueous loading solution does not show any luminescence (the emissi on of Ru(bpy)(2)dppz(2+) in nonaqueous solvents is completely quenched by water), strong emission was detected immediately after immersion o f the Nafion coating. The emission decay is triexponential, with two l ong-lived components (tau = 900 and 300 ns) dominating a fast decay (t au = 50 ns). Emission intensities, lifetimes, and lifetime distributio ns depend strongly on the loading level, owing both to self-quenching and environmental changes brought about by increases in the concentrat ion of the complex in the film. Owing to the remarkable efficiency of excited-state deactivation attributable to dppz-H2O hydrogen bonding, Ru(bpy)(2)dppz(2+) is an extremely sensitive probe of accessible water structures in Nafion.