TIME-RESOLVED FLUORESCENCE OF N,N-DIMETHYLAMINOBENZONITRILE IN GLYCEROL TRIACETATE - EXPERIMENTAL RESULTS AND MODEL INTERPRETATION

Solvatochromic dynamics and internal charge transfer kinetics of dimet hylaminobenzonitrile (DMABN) dissolved in glycerol triacetate (GTA) ha ve been investigated by means of time resolved fluorescence spectrosco py. After pulse excitation in correspondence of the high-frequency abs orption, several dynamical features of the typical dual fluorescence s pectra observed for DMABN in polar solvents are revealed. A precursor successor behaviour for the observed decay of the high-frequency band and the rise of the low-frequency band is detected, and a relevant dyn amic Stokes shift of the low-frequency band is measured. These feature s are rationalized, at a semi-quantitative level, in terms of a stocha stic model in which coupling of the fluorescent probe with the polar e nvironment is explicitly taken in account. Ingredients of the model ar e the potential energy surface for the probe internal coordinates, and hydrodynamic and dielectric properties of the solvent. The comparison of simulations and experimental observations is satisfactory, and fur ther support is given to the interpretation of the internal charge tra nsfer dynamics in DMABN, and homologues, as a reversible interconversi on process with low intrinsic energy barrier and strong coupling to th e solvent environment. (C) 1997 Elsevier Science B.V.