DFT study of ground state proton transfer in 2-pyridone/2-hydroxypyridine–ammonia clusters

Abstract

Abstract DFT calculations in the ground state have been performed for 2-hydroxypyridine–ammonia clusters 2HP · (NH 3 ) n ( n = 1 to 5) and their tautomers. Structures, relative energies and vibrational frequencies of these species were obtained at the B3LYP/6-31++G** level of theory. It was found that some structural parameters such as intra- and intermolecular distances and vibrational frequencies of O–H and N–H stretching, serve as probes and indicators of proton transfer in these clusters. The study of neutral forms shows that intermolecular proton transfer to the (NH 3 ) n occurs for n = 4 and 5 in enol and keto clusters, respectively. For enol form, ion-pair cluster calculated for n = 4 is less stable than the neutral form by 7.1 kJ/mol. While, for keto form, it is calculated to be 25.4 kJ/mol less stable than the neutral form.