| Abstract
| - Competitive ion−dipole, ion−water, and water−water interactions were investigated at the molecular levelin M+(CH3CN)n(H2O)m cluster ions for M = Na and K. Different [n,m] combinations for two different n +m cluster sizes were characterized with infrared predissociation spectroscopy in the O−H stretch region andMP2 calculations. In all cases, no differences were observed between the two alkali metal ions. The resultsshowed that at the n + m = 4 cluster size, the solvent molecules interact only with the ion, and that theinteraction between the ion and the large dipole moment of CH3CN decreases the ion−water electrostaticinteractions. At the n + m = 5 cluster size, at least two different hydrogen-bonded structures were identified.In these structures, the ion−dipole interaction weakens the ability of the ion to polarize the hydrogen bondsand thus decreases the strength of the water−water interactions in the immediate vicinity of the alkali metalion.
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