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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >An Effective Method for Studying Intermolecular Interactions in Binary Liquids with Hydrogen Bonds; FTIR Spectra and Ab Initio Calculations in the N-Methylformamide—Methanol System
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An Effective Method for Studying Intermolecular Interactions in Binary Liquids with Hydrogen Bonds; FTIR Spectra and Ab Initio Calculations in the N-Methylformamide—Methanol System

机译：研究具有氢键的二元液体中分子间相互作用的有效方法; N-甲基甲酰胺-甲醇系统中的FTIR光谱和从头算

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摘要

Molecular complexes in methanol (MeOH)-N-methylformamide (NMF) mixtures were studied based on their FTIR-ATR spectra, to which two methods of analysis were applied: factor analysis and a quantitative version of the difference-spectra method. The mean composition of a complex between NMF and MeOH molecules over the whole range of mixture compositions was determined. Absorbing species differentiated with regard to the interaction energies of the carbonyl oxygen with methanol molecules were recognized in both compositional regions with a marked excess of one component. Possible structures for complexes of various stoichiometrics were optimized by ab initio calculations in the gas phase and both liquid NMF and MeOH using the polarizable continuum model (PCM). Thermodynamic functions calculated for the optimized structures were used to find the most stable structure for each stoichiometry. Individuals distinguished by the spectral analysis were assigned to the complexes of definite composition, and a linear correlation between the positions of the carbonyl group absorption and the total interaction energies of the complexes was found. The results of the spectral analysis of the NMF—MeOH mixtures were compared to those we obtained previously for similar binary systems, i.e., mixtures of methanol and formamide (FA) or N,N-dimethylformamide (DMF). It was shown that the factor analysis applied to the infrared spectra is an effective method for distinguishing molecular complexes with different polarizations of component molecules and allows for the detection of even weak intermolecular interactions and low-concentration species. Combined with the difference-spectra method, factor analysis provides a comprehensive picture of intermolecular interactions in binary mixtures.
机译：基于FTIR-ATR光谱研究了甲醇（MeOH）-N-甲基甲酰胺（NMF）混合物中的分子配合物，并应用了两种分析方法：因子分析和差异光谱的定量形式。确定了在整个混合物组成范围内，NMF和MeOH分子之间的复合物的平均组成。在两个组成区域中识别出在羰基氧与甲醇分子的相互作用能方面有所差异的吸收物质，其中一种成分明显过量。通过使用可极化连续介质模型（PCM）在气相以及液态NMF和MeOH中从头算，可以优化各种化学计量的配合物的可能结构。为优化的结构计算出的热力学函数用于找到每种化学计量最稳定的结构。通过光谱分析区分的个体被分配给确定组成的配合物，并且发现羰基吸收的位置与配合物的总相互作用能之间存在线性关系。将NMF-MeOH混合物的光谱分析结果与我们先前针对类似的二元系统（即甲醇和甲酰胺（FA）或N，N-二甲基甲酰胺（DMF）的混合物）获得的结果进行比较。结果表明，应用于红外光谱的因子分析是区分组分分子不同极化的分子复合物的有效方法，甚至可以检测甚至较弱的分子间相互作用和低浓度物质。结合差异光谱法，因子分析提供了二元混合物中分子间相互作用的全面描述。

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