Solvation dynamics in methanol and n-butanol. Comparison between temperature-dependent fluorescence and dielectric data

Abstract

The temperature dependence of the fluorescence steady-state spectra (intensity and bandshape) and nanosecond lifetimes (τ_f) obtained by light excitation of 2-aminophenyl phenylsulphone in methanol and n-butanol fluid solutions has been examined and compared with that of the Debye (τ_D) and longitudinal (τ_L) relaxation times of the solvents. The temperature range explored for each alcohol is from 300 K to the melting point. Hydrogen-bonding effects, connected to non-radiative paths for the deactivation of the emission from the probe, are reduced at low temperature. The temperature-dependent spectral shifts observed in methanol are ascribed to changes in static polarity of the solvent. The spectral shifts observed in n-butanol are consistent with solvent relaxational dynamics taking place on the τ_L timescale.