Picosecond time-resolved fluorescence spectroscopy is used to probe the formation kinetics of the twisted intramolecular charge-transfer state of bis(4-aminophenyl) sulfone in acetonitrile and alcohol solvents. Emission kinetics were measured at 20-nm intervals from 400 to 560 nm, covering the entire visible region of the emission spectrum. Wavelength-independent rise times were observed in methanol and acetonitrile. In all the longer chain alcohol solvents examined (ethanol to hexanol), wavelength-dependent rise times were observed; longer rise times were observed with decreasing emission energy. In addition, for wavelengths higher in energy than the maximum of the TICT emission maximum, λmax TICT, multiple decay components were observed in all solvents. Only the red edge of the emission (λ > λmax TICT) revealed rises and decays that could be described by single exponentials. The observed kinetics are interpreted in terms of solvent restructuring to stabilize the charge-separated state. Excellent agreement between the fitted rise times of the emission at 500, 540, and 560 nm and the solvent longitudinal relaxation time, τL, is observed.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry