Excited state isomerization kinetics of 4-(methanol)stilbene: Application of the isodielectric Kramers-Hubbard analysis

Trans-4-(methanol)stilbene (HMS) is a member of the diphenylpolyene family with a methanol group appended to one of the phenyl rings of stilbene. In previous studies, we have demonstrated that the polar functional group has a substantial influence on rotational dynamics of HMS in polar liquids and in supercritical CO2. In this paper, we examine the influence of the methanol group on the trans-cis excited state photoisomerization of HMS. We present absorbance and fluorescence spectra that indicate that the spectroscopy of HMS is nearly identical to that of stilbene. We utilize the spectra to calculate the radiative rate constant of the excited-state trans isomer of HMS. Using this result and measured fluorescence lifetimes, we characterize the transcis isomerization rate of HMS in a series of n-alcohols over temperatures from 0 to 60 degreesC. Linear Arrhenius plots are observed over this temperature range. We also present an analysis based on the isodielectric Kramers-Hubbard method originally developed by Anderton and Kauffman. The results of this analysis demonstrate that the barrier to trans-cis isomerization of HMS decreases with increasing solvent permittivity.