Deriving intrinsic parameters of photoinduced electron transfer reaction from the transient effect probed by picosecond time-resolved fluorescence quenching

Fluorescence quenching of a pyrylium salt (PDP2+) by toluene in acetonitril e gives rise to a nonexponential decay. This behavior is ascribed to the so -called transient effect occurring at high quencher concentrations for diff usion-controlled reactions. First, the Kalman filter was used to deconvolut e the original signal from the experimental decay curve and the response fu nction of the apparatus. This treatment led to a calculated deconvoluted de cay curve which enabled the transient effect analysis to be conducted. This real decay curve was then analyzed using two models, The Smoluchowski-Coll ins-Kimball (SCK) model, applied to diffusion-controlled reactions, yielded the reaction radius r(AD) and the intrinsic rate constant k(act) of the bi molecular electron transfer reaction. The Marcus electron transfer/diffusio n (ETD) model, which provides a powerful method to evaluate the electronic coupling H-el associate with the reaction, was also used but is more diffic ult to handle due to extensive computational needs. Finally, the adequacy o f the two models (SCK and ETD) for analysis of the transient effect was add ressed, as well as the appropriateness of the Kalman filter for fluorescenc e signal deconvolution.