Voss Jonathan M, Marsh Brett M, Zhou Jia, Garand Etienne
Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, USA.
Phys Chem Chem Phys. 2016 Jul 28;18(28):18905-13. doi: 10.1039/c6cp02730j. Epub 2016 Jun 29.
The infrared predissociation spectra of bmim·(H2O)n, n = 1-8, in the 2800-3800 cm(-1) region are presented and analyzed with the help of electronic structure calculations. The results show that the water molecules solvate bmim by predominately interacting with the imidazolium C2-H moiety for the small n = 1 and 2 clusters. This is characterized by a redshifted and relatively intense C2-H stretch. For n≥ 4 clusters, hydrogen-bond interactions between the water molecules drive the formation of ring isomers which interact on top of the imidazolium ring without any direct interaction with the C2-H. The water arrangement in bmim·(H2O)n is similar to the low energy isomers of neutral water clusters up to the n = 6 cluster. This is not the case for the n = 8 cluster, which has the imidazolium ring disrupting the otherwise preferred cubic water structure. The evolution of the solvation network around bmim illustrates the competing bmim-water and water-water interactions.
给出并借助电子结构计算分析了bmim·(H2O)n（n = 1 - 8）在2800 - 3800 cm(-1)区域的红外预解离光谱。结果表明，对于n = 1和2的小团簇，水分子主要通过与咪唑鎓C2 - H部分相互作用来溶剂化bmim。这表现为C2 - H伸缩振动的红移和相对较强的强度。对于n≥4的团簇，水分子之间的氢键相互作用促使形成环状异构体，这些异构体在咪唑鎓环顶部相互作用，而与C2 - H没有任何直接相互作用。bmim·(H2O)n中水分子的排列与n = 6团簇以下的中性水团簇的低能量异构体相似。n = 8团簇的情况并非如此，其咪唑鎓环破坏了原本更优的立方水结构。bmim周围溶剂化网络的演变说明了bmim - 水和水 - 水相互作用之间的竞争。
