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-transfered PhO· … H+NH3 configuration.