DENSITY FUNCTIONAL STUDY ON THE PROTON ASSISTED ISOMERIZATION OF 1H-IMIDAZO(4,5-b)PYRIDINE DERIVATIVES

Abstract

The proton assisted isomerization reactions of 1H-imidazo(4,5-b)pyridine (IMP) derivatives have been studied by using B3LYP/6-31G + (d,p) calculations, and the transition states of the reactions are analyzed with B3LYP/6-31+G(d,p) opt=qst3 route. It has been found that the prototropic transformation could be the feasible pathway of isomerization, since the energy gaps between the various protonated isomers are found closer compared to free molecules. The conversion of IMP-a1 to IMP-b1 may pass through several protrotopic isomerization, since the activation energy as well as the relative energy levels of these isomers are not small compared to other pathways. However, the results suggest that some of the reactions may take place simultaneously through protrotopic transformation. The relative variations of energy gaps in the excited states are smaller than the ground states. The protrotropic transformation in the excited states may be more feasible than the ground state.