PHOTOPHYSICAL AND FLUORESCENCE QUENCHING PROPERTIES OF PEROPYRENE IN SOLUTION

The photophysical properties of peropyrene in toluene and acetonitrile solutions at room temperature were investigated with stationary and t ime-resolved fluorescence and absorption measurements. Peropyrene is h ighly fluorescent (Phi(F) = 0.93 in toluene) and exhibits several abso rption and fluorescence spectroscopic features similar to those of per ylene. The absorption spectra of the triplet molecules ((PP)-P-3) and the radical anions ((PP-)-P-2) and cations ((PP+)-P-2) in acetonitril e were recorded. Photoinduced electron transfer reactions between sing let excited peropyrene ((PP)-P-1) and organic electron accepters were investigated in acetonitrile, The reaction between (PP)-P-1 and 1,3- dinitrobenzene (DNB) was studied in more detail. The time-resolved det ection of (PP)-P-3 and (PP+)-P-2 as primary products in the fluoresce nce quenching process allowed the elucidation of the deactivation of t he solvent-separated radical ion pair (SSRIP) (1)((PP+)-P-2...(DNB-)-D -2). The rate constants for the spin-allowed and the spin-forbidden ch arge recombination (CR) reactions were determined to be k(CR)(G) = (4 +/- 2) x 10(10) s(-1) and k(CR)(T) = (6 +/- 3) x 10(8) s(-1). Together with the results from our previous studies of intermolecular electron transfer reactions involving perylene and perylene dyes, these rate c onstants and their dependences on the corresponding free energy change s are discussed within the framework of non-adiabatic electron transfe r theory.