Photochemistry of phenol–(NH3)n clusters: Solvent effect on a radical cleavage of an OH bond in an electronically excited state and intracluster reactions in the product NH4(NH3)n−1 (n⩽5)

Abstract

The potential energy surfaces of PhOH–(NH3)0,1 and NH4(NH3)1–4 have been investigated theoretically by ab initio methods. Intermolecular stretching in PhOH–NH3 assists in the radical cleavage of an OH bond occurring through a ππ*/πσ* potential crossing. Thus, excited state hydrogen transfer (ESHT) is expected to take place by a solvent-assisted mechanism even in the larger PhOH–(NH3)n. Because sufficient energy is obtained by ESHT from PhOH–(NH3)n (ππ*) to PhO–NH4(NH3)n−1 (πσ*) (n⩽5), hydrogen relocation and/or ammonia migration in the product NH4(NH3)n−1 can readily follow ESHT, which is responsible for observing isomer bands in the absorption spectra of the photoinduced reaction products of PhOH–(NH3)n.