Semiclassical molecular dynamics simulations of intramolecular proton transfer in photoexcited 2-(2′-hydroxyphenyl)–oxazole

A full-dimensional excited state potential energy surface is constructed, and the proton transfer dynamics associated with the keto-enolic tautomerization reaction in photoexcited ${\mathrm{2-(2}}^{\prime }\mathrm{-hydroxyphenyl)–oxazole}$ is simulated according to an approximate version of the semiclassical initial value representation method introduced by Miller and co-workers [V. Guallar, V. S. Batista, and W. H. Miller, J. Chem. Phys. 110, 9922 (1999)]. The full-dimensional potential energy surface is developed according to an ab initio reaction surface model obtained at the CIS level of quantum chemistry. Proton transfer is found to be substantially affected by isotopic substitution, and significantly coupled to the internal oxazole–hydroxyphenyl in-the-plane bending mode. The nascent tautomer is found to be stabilized primarily through vibrational energy redistribution into all of the remaining in-the-plane vibrational modes. The accuracy of the methodology is verified by reducing the dimensionality of the system and comparing our semiclassical results with full quantum mechanical calculations.