Vaden Timothy D, Lisy James M
Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
J Phys Chem A. 2005 May 5;109(17):3880-6. doi: 10.1021/jp050534s.
Competitive ion-dipole, ion-water, and water-water interactions were investigated at the molecular level in 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 and MP2 calculations. In all cases, no differences were observed between the two alkali metal ions. The results showed that at the n + m = 4 cluster size, the solvent molecules interact only with the ion, and that the interaction between the ion and the large dipole moment of CH3CN decreases the ion-water electrostatic interactions. 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 bonds and thus decreases the strength of the water-water interactions in the immediate vicinity of the alkali metal ion.
在M+(CH3CN)n(H2O)m簇离子中，对M = Na和K的竞争离子-偶极、离子-水和水-水相互作用进行了分子水平的研究。采用O-H伸缩区域的红外预解离光谱和MP2计算对两种不同n + m簇尺寸的不同[n,m]组合进行了表征。在所有情况下，未观察到两种碱金属离子之间的差异。结果表明，在n + m = 4的簇尺寸下，溶剂分子仅与离子相互作用，并且离子与CH3CN的大偶极矩之间的相互作用降低了离子-水静电相互作用。在n + m = 5的簇尺寸下，至少鉴定出两种不同的氢键结构。在这些结构中，离子-偶极相互作用削弱了离子极化氢键的能力，从而降低了碱金属离子紧邻区域内水-水相互作用的强度。
