Department of Chemical Engineering, Indian Institute of Technology Kanpur, Kanpur, India, 208016.
J Mol Model. 2014 Sep;20(9):2413. doi: 10.1007/s00894-014-2413-3. Epub 2014 Aug 17.
Microstructure of dibenzo-18-crown-6 (DB18C6) and DB18C6/Li(+) complex in different solvents (water, methanol, chloroform, and nitrobenzene) have been analyzed using radial distribution function (RDF), coordination number (CN), and orientation profiles, in order to identify the role of solvents on complexation of DB18C6 with Li(+), using molecular dynamics (MD) simulations. In contrast to aqueous solution of LiCl, no clear solvation pattern is found around Li(+) in the presence of DB18C6. The effect of DB18C6 has been visualized in terms of reduction in peak height and shift in peak positions of g(Li-Ow). The appearance of damped oscillations in velocity autocorrelation function (VACF) of complexed Li(+) described the high frequency motion to a "rattling" of the ion in the cage of DB18C6. The solvent-complex interaction is found to be higher for water and methanol due to hydrogen bond (HB) interactions with DB18C6. However, the stability of DB18C6/Li(+) complex is found to be almost similar for each solvent due to weak complex-solvent interactions. Further, Li(+) complex of DB18C6 at the liquid/liquid interface of two immiscible solvents confirm the high interfacial activity of DB18C6 and DB18C6/Li(+) complex. The complexed Li(+) shows higher affinity for water than organic solvents; still they remain at the interface rather than migrating toward water due to higher surface tension of water as compared to organic solvents. These simulation results shed light on the role of counter-ions and spatial orientation of species in pure and hybrid solvents in the complexation of DB18C6 with Li(+).
采用径向分布函数（RDF）、配位数（CN）和取向分布函数，分析了不同溶剂（水、甲醇、氯仿和硝基苯）中二苯并-18-冠-6（DB18C6）及其与 Li(+)配合物的微观结构，以确定溶剂在 DB18C6 与 Li(+)络合中的作用，采用分子动力学（MD）模拟。与 LiCl 的水溶液不同，在存在 DB18C6 的情况下，Li(+)周围没有发现明显的溶剂化模式。DB18C6 的影响表现在 g(Li-Ow)的峰高降低和峰位移动。复合 Li(+)的速度自相关函数（VACF）中出现阻尼振荡，描述了离子在 DB18C6 笼中的高频运动到“摇晃”。由于与 DB18C6 发生氢键（HB）相互作用，水和甲醇中的溶剂-配合物相互作用较高。然而，由于弱的配合物-溶剂相互作用，DB18C6/Li(+)配合物在每种溶剂中的稳定性几乎相似。此外，两种不混溶溶剂的液/液界面上的 DB18C6/Li(+)配合物证实了 DB18C6 具有高界面活性和 DB18C6/Li(+)配合物。与有机溶剂相比，复合的 Li(+)对水具有更高的亲和力；然而，由于水的表面张力比有机溶剂高，它们仍留在界面上，而不是迁移到水中。这些模拟结果阐明了抗衡离子和物种的空间取向在 DB18C6 与 Li(+)络合中的纯溶剂和混合溶剂中的作用。
