Quenching of photoexcited Ru(bpy)32+by a hydrazone derivative in a poly(ethylene oxide) film

Abstract

The quenching of photoexcited Ru(bpy)₃²⁺ by 2-methyl-4-(N,N′-dibenzylamino)benzaldehyde-N-2-benzothiazolyl-N-n-butylhydrazone (BBTH) in a poly(ethylene oxide) film has been studied. To determine which quenching model can be applied to the present system, the emission quenching and emission decay under various BBTH concentrations were measured. Plots based on relative emission quantum yield showed a downward deviating curve and could not be analyzed by the 13 quenching models reported hitherto. To analyze this quenching reaction, a new model involving static and dynamic mechanisms was proposed which takes into account the dependence of the static quenching rate on the quencher concentration incorporated into a quenching sphere specific for a solid system. The best fit was obtained when the static quenching rate was proportional to the one-third power of the quencher concentration present in the quenching sphere. As a result of this treatment, the quenching distance was found to be 1.7 nm, the static quenching rate constant (k_q1) 1.3 × 10⁵ s⁻¹ and the dynamic quenching rate constant (k_q2) 8.6 × 10⁶ d mol⁻¹ s⁻¹.