CHEMICAL-REACTIONS IN CLUSTERS

Four different classes of cluster chemical reactions are reviewed and specific examples from our laboratory are given for each class. Solvent induced electron-transfer reactions are illustrated by our studies of 4-(dimethylammo)benzonitrile/acetonitrile clusters. The electron-transfer reaction depends on solvent polarity and on cluster structure. The reaction is induced by only one properly oriented CH3CN solvent molecule. Proton-transfer reactions in neutral clusters are exemplified by the 1-naphthol/ammonia cluster system. Proton transfer occurs in the first excited singlet state of the 1-naphthol (NH3)3 Cluster of the proper geometry. Two time decays are measured for this event: one dealing with proton transfer and the other with "solvent reorganization or relaxation" following the transfer event. Isotope, energy, cluster size dependence, and model calculations demonstrate a proton tunneling mechanism is appropriate for this reaction. Cluster ion chemistry for toluene, toluene-d3, benzyl alcohol, benzyl-alpha, alpha-d2 alcohol, alpha,alpha-dimethylbenzyl alcohol/ammonia and water clusters is also discussed. These ionic reactions are characterized by benzyl-like radical formation, solvation of protons, and extensive cluster fragmentation following both ion formation and proton transfer. Finally, a preliminary study of radical reactions in clusters is presented for the benzyl radical clustered with ethylene, propylene, and acetylene.