Dependence of Photochemical Reactivity of the All‐trans Retinal Protonated Schiff Base on the Solvent and the Excitation Wavelength

Abstract

An all-optical experimental technique aimed at measuring photoisomerization quantum yield (phi) of the all-trans protonated Schiff base of retinal in solution has been implemented. Upon the increase in the excitation wavelength from 400 to 540 nm a slight increase in phi from 0.16 +/- 0.03 to 0.20 +/- 0.02 is observed in the chromophore dissolved in methanol, whereas the phi value of the one dissolved in acetonitrile varies only from 0.22 +/- 0.03 (400 nm) to 0.23 +/- 0.04 (540 nm). The results suggest that dissipation of the excited-state vibrational energy excess, along with environment-induced modifications of the potential energy surfaces are necessary for an efficient retinal photoisomerization in both solvent and protein environment.