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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >NMR and Quantum Chemistry Study of Mesoscopic Effects in Ionic Liquids
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NMR and Quantum Chemistry Study of Mesoscopic Effects in Ionic Liquids

机译：离子液体中介观效应的NMR和量子化学研究

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1H, 13C, and 81Br NMR spectra of the neat room-temperature ionic liquid (RTIL), namely, 1-decyl-3-methylimidazolium bromide ([C10mim][Br]) as well as its solutions in acetonitrile, dichloromethane, methanol, and water have been investigated. The most important observation of the present work is the significant broadening of 81Br NMR signal in the solutions of [C10mim][Br] in organic solvents, which molecules tend to associate into hydrogen bond networks and the appearance of the complex contour of 81Br NMR signal in the neat RTIL as well as in the liquid crystalline (LC) ionogel formed in RTIL/water solution. The complex structure of 81Br signal changes upon heating and dilution in water. It disappears at ca. 353 K and in the aqueous solution below ca. 0.1 mol fraction of RTIL. Several new 1H NMR signals appear at the [C10mim][Br]/water compositions just before the solidification of the sample (0.3 mol fraction of [C10mim][Br]). These additional peaks can be attributed to the H2O protons placed in inhomogeneous regions of the sample or due to the appearance of nonequivalent water sites in LC ionogel, the exchange between which is highly restricted or even frozen. The complex shape of 81Br NMR signal can originate from the presence of supra-molecular structures (mesoscopic domains) that live over the period of the NMR time-scale due to a very high viscosity of [C10mim][Br]. These domains exhibit some features of partially disordered solids (liquid- or plastic crystals). To evaluate the static and dynamic contributions into the relaxation rate of 81Br nuclei, the quantum chemistry calculations of the electronic structure, magnetic shielding, and electric field gradient (EFG) tensors of [C10mim][Br] and related model systems (Br- ·6H2O cluster, with addition of the dipoles (hydrogen fluoride) and charged particles - cations: H+ or C1mim+) were performed.
机译：室温纯离子液体（RTIL），即1-癸基-3-甲基咪唑鎓溴化物（[C10mim] [Br]）及其在乙腈，二氯甲烷，甲醇中的溶液的1H，13C和81Br NMR光谱和水已经过调查。在本研究中，最重要的观察结果是[C10mim] [Br]在有机溶剂中的溶液中81Br NMR信号的显着拓宽，该分子倾向于缔合成氢键网络和出现81Br NMR信号的复杂轮廓在纯净的RTIL中以及在RTIL /水溶液中形成的液晶（LC）离子凝胶中。 81Br信号的复杂结构会在加热和在水中稀释后发生变化。它消失在约。 353 K，并在水溶液中低于ca。 0.1摩尔分数的RTIL。刚好在样品固化之前，[C10mim] [Br] /水组合物中出现了几个新的1H NMR信号（[C10mim] [Br]为0.3摩尔分数）。这些额外的峰可以归因于放置在样品非均质区域中的H2O质子，或者归因于LC离子凝胶中不等价水位点的出现，它们之间的交换受到严格限制甚至冻结。 81Br NMR信号的复杂形状可能源于由于[C10mim] [Br]的极高粘度而存在于NMR时间范围内的超分子结构（介观域）。这些结构域表现出部分无序的固体（液晶或塑料晶体）的某些特征。为了评估对81Br核弛豫速率的静态和动态贡献，[C10mim] [Br]的电子结构，磁屏蔽和电场梯度（EFG）张量的量子化学计算以及相关模型系统（Br-·进行了6H2O团簇，添加了偶极子（氟化氢）和带电粒子-阳离子：H +或C1mim +。

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