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 spectrosc opy using synchrotron radiation and a photoelectron photoion coincidence de tection technique. The proton abstraction by the base (PhOH ... (NH3)(n) do uble left right arrow PhO- ... H+(NH3)(n)) depends on the proton affinity o f 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 t he light of these new results. (C) 1999 Elsevier Science B.V. All rights re served.