Photoinduced charge recombination reactions of a perylene dye in acetonitrile

In the present study, the photophysical properties of the perylene dye PBI [N,N′-bis(1-hexylheptyl)-3,4:9,10-perylenebis(dicarboximide)] and the quenching of PBI fluorescence by organic quencher molecules in acetonitrile was investigated with stationary and time-resolved fluorescence and absorption measurements. On the basis of a simplified reaction scheme, a comprehensive analysis of the fluorescence quenching process was achieved for 8 PBI–quencher molecular pairs for which the formation of free PBI ions was observed. It is notable that both the anionic and cationic species (2PBI-, 2PBI+) were detected as primary products of the intermolecular ElT processes. Together with other data from our group and by Mataga etal. (Chem. Phys., 1988, 127, 249) an evaluation of the results within the framework of the Marcus theory of non–adiabatic electron transfer was performed. It was found that with an overall variation of the standard free energy changes for the charge recombination (CR) reaction to the PBI ground (ΔGCRG) and triplet states (ΔGCRT) of more than 2 eV the CR reaction rate constants cover the whole energetic range of the non-adiabatic electron transfer, i.e. from the normal to the Marcus inverted regime.