Isolating the Charge-Transfer Component of the Anionic H Bond Via Spin Suppression of the Intracluster Proton Transfer Reaction in the NO<SUP>-</SUP>·H<INF>2</INF>O Entrance Channel Complex

We report the vibrational predissociation spectrum of the NO^-·H<INF>2</INF>O complex in the OH stretching region. The ionic H-bonded OH stretch is much less red-shifted and less structured in the vibrational spectrum of NO^-·H<INF>2</INF>O than in that of the O<INF>2</INF>^-·H<INF>2</INF>O cluster, despite the larger proton affinity of NO^- relative to O<INF>2</INF>^-. It is argued that the differences between the spectra of these two species are primarily a consequence of the greater charge-transfer character in the O<INF>2</INF>^-·H<INF>2</INF>O cluster and that the charge-transfer component is much less important in NO^-·H<INF>2</INF>O because of its triplet spin character.