Photochemistry of phenol(NH_3)_n clusters: Solvent effect on a radical cleavage of an OH bond in an electronically excited state and intracluster reactions in the product NH_4(NH_3)_n-1(n =5)

摘要

The potential energy surfaces of PhOH-(NH_3)_0.1 and NH_4(NH_3)-1-4 have been investigated theoretically by ab initio methods. Intermolecular stretching in PhOH-NH_3 assists in the radical cleavage of an OH bond occurring through a pi pi*/pisigma* potential crossing. Thus, excited state hydrogen transfer (ESHT) is expected to take place by a solvent-assisted mechanism even in the larger PhOH-(NH_3)_n. Because sufficient energy is obtained by ESHT from PhOH-(NH_3)_N(pi pi*) to PhO-NH_4(NH_3)_N-1(pi sigma*)(n<=5), hydrogen relocation and/or ammonia migration in the product NH_4(NH_3)_n-1 can readily follow ESHT, which is responsible for observing isomer bands in the absorption spectra of the photoinduced reaction products of PhOH-(NH_3)_n.