Solvent dielectric effects on isomerization dynamics: Investigation of the photoisomerization of 4,4′-dimethoxystilbene and t-stilbene in n-alkyl nitriles

New data for the photoisomerization dynamics of t-stilbene and 4,4′-dimethoxystilbene in polar solvents are reported. These data demonstrate that in n-alkyl nitriles, nonassociated polar solvents, it is possible to extract a solvated barrier for the isomerization. This result is contrasted with recent studies in n-alkyl alcohols, associated polar solvents, where this separation is not possible and clarifies the origin of the changing barrier height in n-alkyl alcohols. Comparison of reduced isomerization rates with models of chemical reaction dynamics in solution are drawn. Good agreement of the data with a coupled oscillator model is found.