Deciphering the role of multiple hydrogen bonding sites on the microsolvation of 3-(phenylamino)-2-cyclohexen-1-one with water in the excited states

Abstract

We report here our investigations on the H-bonding modifications of molecular electronic structures and properties of 3-(phenylamino)-2-cyclohexen-1-one (PACO) and its 1:3 microhydrated cluster in the ground (S0) and first two excited states (S1 and S2). The changes in bond lengths, atomic charges, natural bond order and aromaticity in the S0, S1 and S2 states have been analysed. The electronic state dependence of the hydrogen bonding strengths at different H-bonding sites of PACO has been looked into. The hydrogen bonds formed through the H-bond accepting carbonyl moiety in PACO.3H2O cluster appears to get weaker in the excited states while that formed through the H-bond donating amino moiety gets much stronger, compared to their ground state counterpart. The simultaneous strengthening of H-bonds at one site and weakening at another in the S1 and S2 states may have link to the overall stabilization of the clusters in the excited states relative to the ground state as observed experimentally.