Effects of the Wire Length on H-Atom Transfer in 7-Hydroxyquinoline·(NH3)n: n = 2 and 3

Abstract

Previously we have employed the 7-hydroxyquinoline·(NH3)n ammonia-wire clusters to study excited state H-atom transfer along a sequence of hydrogen bonds. H-atom transfer experimentally occurs for n = 4 excited to its vibrationless S1 state, for n = 3 with additional excitation of ammonia-wire vibrations (~200cm–1). However, for the n = 2 cluster, no reaction is observed, even with additional excitation energy of 900cm–1. CIS calculations have been performed on the n = 2 and n = 3 clusters to understand the effect of the wire length on the energy profile of the reaction. The enol ? keto reaction is always exoergic, and the barrier for H transfer to the proximal ammonia controls the reaction kinetics.