Effects of poly(vinyl sulfate) on the decay of excited tris(2,2′-bipyridine)ruthenium(II) in aqueous solutions followed by the pulsed laser technique

Both the emission of the so-called "triplet" of Ru(bpy)₃²⁺, ³CT Ru(bpy)₃²⁺, at 600 nm and the bleaching of its ground state at 480 nm were followed by pulsed laser techniques. The effect of addition of poly(vinyl sulfate) (PVS) was investigated. Three decay reactions of ³CT Ru(bpy)₃²⁺ were observed: a fast process with a half-life of the order of 10^-8 s accounted for the decay of a significant fraction of the ³CT Ru(bpy)₃²⁺. This was followed by a mixed first and second-order decay of the ³CT Ru(bpy)₃²⁺ which remained after the end of the fast process. The results are discussed in terms of a triplet-triplet annihilation reaction which occurs due to the concentration effect by the polyelectrolyte. When less than four ³CT Ru(bpy)₃²⁺ ions are present, on the average, in each polymer molecule, the only reaction observed is the "natural" decay of ³CT Ru(bpy)₃²⁺, with a rate equal to that observed in the absence of PVS.