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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Solute Rotation in Ionic Liquids: Size, Shape, and Electrostatic Effects
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Solute Rotation in Ionic Liquids: Size, Shape, and Electrostatic Effects

机译：离子液体中的溶质旋转：尺寸，形状和静电效应

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Herein are reported temperature-dependent measurements and molecular dynamics simulations designed to investigate the effects of molecular size, shape, and electrostatics on rotational dynamics in ionic liquids. Experiments were performed in the representative ionic liquid 1-butyl-3-methylimadazolium tetrafluoroborate ([Im(41)][BF4]) and simulations in the generic ionic liquid model ILM2 as well as a more detailed representation of [Im41][BF4]. H-2 longitudinal spin relaxation times (T-1) were measured for deuterated versions of 1,4-dimethylbenzene, 1-cyano-4-methylbenzene, and 1,4-dimethylpyridinium between 296 and 337 K. Fluorescence anisotropy measurements were made on the larger solutes 9,10-dimethylanthracene, 9-cyano-10-methylanthracence, and 9,10-dirnethylacridnium between 240 and 292 K. Both experiment and simulation showed the nonpolar solutes rotate similar to 2-fold faster than.. their dipolar and charged counterparts. The rotational correlation functions measured in fluorescence experiments are significantly nonexponential and can be fit to stretched exponential functions having stretching exponents 0.4 <= beta <= 0.8, with beta decreasing with decreasing temperature. Rotational correlation times in both the NMR and fluorescence experiments conform approximately to the hydrodynamic expectation tau(rot) alpha (eta/T)(p) with p congruent to 1, and observed times are reasonably close to slip hydrodynamic predictions. Simulations, even with the idealized ILM2 solvent model, are in semiquantitative agreement with experiment when compared on the basis of equal values of eta T-1. When rotational diffusion coefficients (D-i) rather than correlation times were considered, much larger departures from hydrod-ynamic predictions are found in many cases (p similar to 0.5 and D-i slip predictions). Rotational van Hove functions and trajectory analyses reveal the importance of large-angle jumps about some axes, even in the larger solutes.
机译：本文是报告的温度依赖的测量和分子动力学模拟，旨在研究分子大小，形状和静电在离子液体中的旋转动力学上的影响。实验在代表性离子液体1-丁基-3-甲基亚硝氮唑鎓四氟硼酸盐（[IM（41）] [BF4]）中进行，并且在通用离子液体模型ILM2中的模拟以及[IM41] [BF4]的更详细的表示。测量H-2纵向旋转弛豫时间（T-1），用于1,4-二甲基苯，1-氰基-4-甲基苯的氘代型，和296和337K之间的1,4-二甲基吡啶鎓。荧光各向异性测量较大的溶质9,10-二甲基蒽，9-氰基-10-甲基蒽，和9,10-甲基丙烯丙啶，两者在240和292k之间。两种实验和模拟显示，非极性溶质旋转与2倍的速度相似。它们的双极和收费的同行。在荧光实验中测量的旋转相关函数显着下表现，并且可以适合具有拉伸指数的拉伸指数函数0.4 <=β<= 0.8，β降低温度。 NMR和荧光实验中的旋转相关时间大致致力于与P一致为1的流体动力期望tau（腐甲酸）α（eta / t）（p），并且观察时间合理地接近滑动流体动力学预测。仿真，即使是理想化的ILM2溶剂模型，在基于ETA T-1的等值的基础上与实验中的半定量协议。当考虑旋转扩散系数（D-1）而不是相关时间，在许多情况下发现了来自Hydrod-Y键样预测的大大偏离（P类似于0.5和D-1 滑动预测）。旋转范索函数和轨迹分析揭示了大角度跳跃关于一些轴的重要性，即使在较大的溶质中也是如此。

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