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The infrared spectra of protic ionic liquids: performances of different computational models to predict hydrogen bonds and conformer evolution
Physical Chemistry Chemical Physics ( IF 3.3 ) Pub Date : 2020/03/19 , DOI: 10.1039/d0cp00907e
O. Palumbo 1, 2, 3, 4 , A. Cimini 1, 2, 3, 4 , F. Trequattrini 1, 2, 3, 4, 5 , J.-B. Brubach 6, 7, 8 , P. Roy 6, 7, 8 , A. Paolone 1, 2, 3, 4
Affiliation  

The temperature dependence of the far- and mid-infrared spectrum of two prototypical protic ionic liquids (PILs) sharing a common trialkylammonium cation, but having different anions, is investigated. The exploitation of both the FIR and MIR ranges provides complementary information about the microscopic configurations and the intermolecular interactions, which determine the structure and the properties of ILs. The analysis of the data collected for all the measured frequencies in a wide temperature range reveals several phase transitions and allows the evaluation of the conformer distribution in the different physical states. The difference in the average energy between the H-bonded configurations and the dispersion-governed ones was also determined for the two PILs. Moreover, a computational model for ionic couples based on the ωB97X-D functional and a polar solvent is here successfully exploited for the description of the hydrogen bonding between anion and cation. For the attribution of vibrational lines of the conformers of the cation, the picture based on single ion calculations at the B3LYP level is more valuable and provides better agreement with the experiments.

中文翻译:

质子离子液体的红外光谱:预测氢键和构象异构体进化的不同计算模型的性能

研究了两种具有共同的三烷基铵阳离子但具有不同阴离子的原型质子离子液体(PIL)的远红外光谱和中红外光谱的温度依赖性。FIR和MIR范围的利用提供了有关微观构型和分子间相互作用的补充信息,这些信息决定了IL的结构和性质。对在宽温度范围内所有测得的频率收集的数据进行的分析揭示了几个相变,并允许评估不同物理状态下的构象异构体分布。还确定了两个PIL的H键构型和分散控制的构型之间的平均能量差。此外,本文成功地利用基于ωB97X-D官能团和极性溶剂的离子对计算模型来描述阴离子和阳离子之间的氢键。对于阳离子构象体的振动线的归因,基于B3LYP级别的单离子计算的图片更有价值,并且与实验更加吻合。
更新日期:2020-04-08
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