Proton transfer between phenol and ammonia in ground and excited electronic states

Ab initio calculations consider the H-bonded complex between phenol and ammonia. The transfer of a proton in the ground electronic state, which would form PhO(-)...+HNH3, is highly disfavored. However, the situation changes dramatically in the first excited singlet state where the proton transfer potential develops a second minimum, competitive in energy with the neutral pair PhOH ... NH3. Following electron ejection, the radical cation complex, PhOH(+)... NH3, contains a very flat proton transfer potential connecting PhOH(.+)... NH3 with PhO(.)... H+NH3. Addition of more ammonia molecules further stabilizes the proton-transferred PhO(.)... H+NH3 configuration.