Application of reaction path concept in intramolecular proton transfer

Abstract

Intramolecular proton transfer in the ground state and the first singlet excited state are investigated on ab initio level using 2(2′-hydroxyphenyl)-imidazoline as a model compound. The reaction-path concept is applied and new descriptions of the proton positions are proposed. The full calculations show surprising differences between the method using mass-weighted internals and mass-weighted Cartesian coordinates. In the simplified “static” approach the results are dependent on the choice of the reaction coordinate. If the choice is made with care, the results comparable with full intrinsic reaction coordinate search are obtained. The concerted reaction-path calculations are justified only in the vicinity of the transition state.