Protonation effect on the electronic properties of 2-pyridone monomer, dimer and its water clusters: A theoretical study

Abstract

The CC2 (second order approximate coupled cluster method) has been applied to investigate protonation effect on electronic transition energies of 2-pyridone (2PY), 2-pyridone dimer, and micro-solvated 2-pyridone (0-2 water molecules). The PE profiles of protonated 2-pyridone (2PYH) as well as monohydrated 2PYH at the different electronic states have been investigated. The 1πσ state in protonated species (2PYH) is a barrier free and dissociative state along the O-H stretching coordinate. In this reaction coordinate, the lowest lying 1πσ predissociates the bound S1(1ππ) state, connecting the latter to a conical intersection with the S0 state. These conical intersections lead the 1ππ state to proceed as predissociative state and finally direct the excited system to the ground state. Furthermore, in presence of water molecule, the 1πσ state still remains dissociative but the conical intersection between 1πσ and ground state disappears. In addition, according to the CC2 calculation results, it has been predicted that protonation significantly blue shifts the S1-S 0 electronic transition of monomer, dimer, and microhydrated 2-pyridone. © 2014 AIP Publishing LLC.