Photoinduced intramolecular charge transfer of 3-cyano-4-furyl-6-phenyl-2-(9-anthralylidene)-pyridine

Abstract

The absorption and fluorescence spectra, fluorescence quantum yields and lifetimes of 3-cyano-4-furyl-6-phenyl-2-(9-anthralylidene)-pyridine (FPAP) in various solvents are reported. The results show that the quantum yield of the fluorescence ( Φ f) of FPAP is high and decreased with increasing solvent polarity. The fluorescence decay time is almost single exponential, independent of the excitation wavelength and its value decreases upon increasing the solvent polarity. The radiative rate constant ( k r), however, shows a maximum value for solvents of intermediate polarity, e.g. in CHCl 3 a value of 2.1×10 8 s −1 is attained. However, k nr value increases with increasing solvent polarity. The bathochromic shift of the emission spectra and the resulting increase in the excited state dipole moment indicate the charge transfer (CT) character of the emitting singlet state of FPAP. The relatively large values of k r and the corresponding transition dipole moment ( M f) indicate the absence of a twist intramolecular charge transfer in the fluorescent states.