Theoretical study on the isomerization process of retinal in gas and aqueous phase

Abstract

B3LYP/6-311++G(d,p) level of theory was carried out to explain the isomerization process of retinal stereoisomer based on the structural and molecular properties in gas phase and implicit aqueous environment. Frequency calculations on the fully optimized molecular geometries of the retinal isomers confirmed them to be true minima. The relative energies, dipole moments, bond orders, theoretically predicted vibrational frequencies, and HOMO–LUMO energy gaps of the retinal isomers were analyzed. The influence of the explicit aqueous environment on the geometrical parameters associated with the geometry of polyene chain and the vibrational spectra of retinal isomers were evident. The geometries of 11-cis and all-trans retinal isomers exhibited delocalized bonds along the polyene chain in the aqueous phase with a pattern of longer double bonds and shorter single bonds. The vibrational frequencies of the retinal isomers calculated at the B3LYP level of theory were in better agreement with the experimental values in the gas phase. The method and results presented in this study may help to better understand the effects of environment on its isomerization process.