Proton-transfer reaction in the ground state of phenol–ammonia clusters: an experimental study

The proton-transfer reaction in the ground state of phenol–ammonia clusters [PhOH(NH3)n] has been investigated by single-photon ionization spectroscopy using synchrotron radiation and a photoelectron photoion coincidence detection technique. The proton abstraction by the base (PhOH⋯(NH3)n⇔PhO−⋯H+(NH3)n) depends on the proton affinity of ammonia clusters which increases with their size. The present experiment demonstrates that at least six ammonia molecules clustered with phenol are necessary to displace the equilibrium and induce the proton transfer in the ground state. The previous nanosecond and picosecond experiments on proton transfer occurring in the excited state of PhOH(NH3)n are discussed in the light of these new results.