Observation of a catalytic proton/hydrogen atom relay in microsolvated 7-azaindole-methanol cluster enhanced by a cooperative motion of the hydrogen-bonded network

Abstract A catalytic multiple-proton/hydrogen atom relay in the 7-azaindole-methanol cluster (7AI(MeOH) n , n  = 1–3) has been investigated in the gas phase by measuring the mass-resolved vibronic spectra and the dispersed fluorescence spectra of 7AI(MeOH) n ( n  = 1–3). It has been found that the observation of the visible fluorescence due to the multiple-proton/hydrogen atom relay is cluster-size selective; 7AI(MeOH) 2 undergoes an efficient triple-proton/hydrogen atom relay on a ππ ∗ and/or πσ ∗ surface. The triple-proton/hydrogen atom relay in this cluster also exhibits prominent vibrational-mode selectivity. The excitation of an intermolecular stretch mode (σ 1 ) with the in-phase cooperative motion of the whole hydrogen-bond network accelerates the proton/hydrogen atom relay.