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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Interaction of Water Highly Diluted in 1-Alkyl-3-methyl Imidazolium Ionic Liquids with thePF_6-and BF_4-Anions
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Interaction of Water Highly Diluted in 1-Alkyl-3-methyl Imidazolium Ionic Liquids with thePF_6-and BF_4-Anions

机译：在1-烷基-3-甲基咪唑鎓离子液体中高度稀释的水与PF_6-和BF_4-阴离子的相互作用

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摘要

We have investigated water highly diluted in 1-alkyl-3-methyl imidazolium ionic liquids (ILs) withhexafluorophosphate { PF_6~-} and tetrafluoroborate { BF_4~- } anions using vibrational spectroscopic measurementsin the |í_(OH)spectral domain of water (3600-3800 cm~(-1)) and DFT calculations. The measured profiles exhibittwo well-defined bands at coinciding vibrational transitions assigned with the v1 symmetric and |í_3antisymmetricOH stretching modes of monodispersed water. The local organization and the vibrational spectra of waterdiluted in ILs have been assessed by DFT calculations (using the B3LYP functional and 6-31+G~(**) basisset). We show that the predicted structures of water interacting (minimally) with two anions in nearly"symmetric" structures of type (A?- H-O-H?-A) lead to spectral features consistent with the previousspectroscopic observations as well as with those reported here. We emphasize the role of the non additiveinteraction forces (especially the 3-bodies electrostatic interactions) in the structural organization taking placebetween the cation-anion couples and for determining preferentially (A?-H-O-H?-A) associations ofwater with the anions as well as their consequences on the vibrational spectra of water. We show that thedoubly hydrogen-bonded character of water in such associations leads to well-defined spectral features, whichare the shifts of the |í_1and |í_3stretching modes of water, the separation ¤í_(13)between them (about 80 cm~(-1) ),and the intensity ratio estimates R = I|í_3/I|í_1(IR absorption and Raman). Finally, we evoke the fact that theH-bond interactions of water diluted in these ILs involve a more noticeable electrostatic character than forH-bond interactions of water in usual molecular solvents. In this context, we emphasize that the appearanceof the Raman band of the |í_3mode of water originates from a significant polarization of water due to the localelectrostatic fields induced by surrounding ions.
机译：我们使用振动光谱法在水的|í_（OH）光谱域中研究了在六烷基磷酸根{PF_6〜-}和四氟硼酸根{BF_4〜-}阴离子的1-烷基-3-甲基咪唑鎓离子液体（ILs）中高度稀释的水（3600） -3800 cm〜（-1））和DFT计算。测得的轮廓在一致的振动跃迁处表现出两个清晰的带，这些振动跃迁被分配给单分散水的v1对称和|í_3antisymmetricOH拉伸模式。通过DFT计算（使用B3LYP函数和6-31 + G〜（**）基集）评估了离子液体中水稀释的局部组织和振动谱。我们表明，预测的水结构（与最小限度地）与（A 2-H-O-H 2 -A）几乎“对称”结构中的两个阴离子相互作用的结构导致光谱特征与以前的光谱观察结果以及此处报道的一致。我们强调非加成相互作用力（尤其是三体静电相互作用）在阳离子-阴离子对之间发生的结构组织中的作用，以及优先确定水与阴离子以及阴离子的缔合（Aβ-HOHβ-A）的作用。它们对水的振动谱的影响。我们表明，水在这种缔合中的双重氢键键合特征导致了明确定义的光谱特征，即水的|í_1和|í_3拉伸模式的位移，它们之间的间距íí_（13）（约80 cm〜（- 1）），强度比估计值R = I |í_3/ I |í_1（红外吸收和拉曼光谱）。最后，我们得出这样一个事实：在这些分子束中稀释的水的氢键相互作用比普通分子溶剂中水的氢键相互作用具有更明显的静电特性。在这种情况下，我们强调水的|π_3模的拉曼谱带的出现是由于周围离子引起的局部静电场，导致水的明显极化。

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