Effect of medium dynamics on the process of electron transfer in bianthryl molecule

The parameters of charge phototransfer in a bianthryl molecule and the relaxation shifts in its charge transfer fluorescence spectra in ethanol and glycerin are studied in the temperature range from 77 to 340 K. In the low-temperature range, the efficiency of phototransfer is close to zero because the rate of the process of relaxational solvation is slow as compared with that of deactivation of an excited photoactive state. With growing temperature, the efficiency of charge phototransfer in bianthryl (K_rel) becomes noticeably temperature dependent. In glycerol, K_rel correlates with the relaxation shift parameter, P_v, which reflects the bulk relaxation dynamics of the solvent. In ethanol, K_rel correlates with the corresponding parameter P of the relaxation of solvent molecules near the singlet-excited chromophor. These results allowed formulation of the mechanism of charge phototransfer in bianthryl in the solvents studied. The data obtained show the important role of relaxation processes in a medium in the formation of the energy relief favorable for charge phototransfer.