Theoretical study on conformation dynamics of three-station molecular shuttle in different environments and its influence on NMR chemical shifts and binding interactions.
Theoretical study on conformation dynamics of three-station molecular shuttle in different environments and its influence on NMR chemical shifts and binding interactions.
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DOI：
10.1021/jp5020516
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发表时间：
2014-07
期刊：
影响因子：
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通讯作者：
Pingying Liu;Wei Li;Li Liu;Leyong Wang;Jing Ma
中科院分区：
文献类型：
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作者：
Pingying Liu;Wei Li;Li Liu;Leyong Wang;Jing Ma
构象灵活性和大环线结合相互作用的微观信息有助于合理设计具有有趣的拓扑结构和功能的新型多站分子梭。应用分子动力学（MD）方法模拟了三工位分子梭在不同化学环境（真空、CD 3CN-CDCl 3溶液和晶体）中的螺旋和大环构象变化。与在气相和非极性CDCl 3溶液中的高度扭曲的线构象相比，在CD 3CN-CDCl 3（1：1）混合溶剂中的溶剂化线呈现出相对刚性的结构。在质子化的二苄基铵基团（站I）的优先结合的实验观察合理化的大环线程结合能在三个不同的站的量子化学计算。在三个不同的站点的位点特异性结合相互作用的正交性也揭示了在每个特定的识别中心与不同的相邻基团和终端的线程上的塞子的替代获得的几乎恒定的结合能。构象柔性对结合位点的NMR信号影响很小，但对于第一溶剂壳层中靠近溶剂分子的一些质子，其化学位移对附近溶剂引起的局部静电环境很敏感。在晶体中，π堆积引起NMR信号明显的高场位移。
Microscopic information on conformational flexibility and macrocycle-thread binding interactions is helpful in rational design of novel multistation molecular shuttles with interesting topology and functions. Molecular dynamics (MD) was applied to simulate conformational changes of thread and macrocycle of a three-station molecular shuttle in different chemical environments (vacuum, CD3CN-CDCl3 solution, and crystal). In contrast with the highly distorted thread conformation in the gas phase and nonpolar CDCl3 solution, the solvated thread in CD3CN-CDCl3 (1:1) mix solvents exhibited a relatively rigid structure. Experimental observations of preferential binding at the protonated dibenzylammonium group (station I) were rationalized by quantum chemical calculations of macrocycle-thread binding energies at three different stations. The orthogonality of site-specific binding interactions at three different stations was also revealed by the nearly constant binding energy obtained at each specific recognition center with the replacement of different neighboring groups and terminal stoppers on the thread. Conformational flexibility has little effect on NMR signals of binding sites, but for some protons that are close to the solvent molecules in the first solvent shell, their chemical shifts are sensitive to the local electrostatic environment caused by nearby solvents. In crystal, π stacking induced evident upfield shifts of NMR signals in comparison with the isolated monomer.