Stereospecificity of quenching of excited aromatic molecules by electron acceptors

On the example of fluorescence quenching of perylene by organic electron acceptors we have shown that the radius of the quenching sphere depends on the electron affinity of the oxidizing agent. The deactivation of excited molecules of m-dinitrobenzene was achieved by tunnel electron transfer at a distance, which was significantly greater than the sum of the radii of the reagent molecules. The fluorescence quenching with phthalic anhydride, a weaker electron acceptor, occurs on contact between molecules. The kinetics of this process are described by the Smoluchowski theory of diffusion-controlled reactions. The rate of fluorescence quenching with carbon tetrachloride and nitromethane in polar solvents also increases with the increase of the coefficients of mutual diffusion, but the formal reaction radii of these processes are smaller than the sum of the radii of the interacting particles, which is due to the stereospecifity of the reaction. It was shown that the degree of stereospecificity increases with the decrease of the reaction radius.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 22, No. 5, pp. 585–590, September–October, 1986.