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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Harmonic and Anharmonic Features of IR and NIR Absorption and VCD Spectra of Chiral 4-X-[2.2]Paracyclophanes
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Harmonic and Anharmonic Features of IR and NIR Absorption and VCD Spectra of Chiral 4-X-[2.2]Paracyclophanes

机译：手性4-X- [2.2]吡咯烷酮的红外和近红外吸收和VCD光谱的谐波和非谐特征

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摘要

The vibrational absorption spectra and vibrational circular dichroism (VCD) spectra of both enantiomers of 4-X-[2.2]paracyclophanes (X = COOCD3, Cl, I) have been recorded for a few regions in the range of 900~(-1)2000 cm~(-1). The analysis of the VCD spectra for the two IR regions, 900~(-1)600 cm~(-1) and 2800-3200 cm~(-1), is conducted by comparing with DFT calculations of the corresponding spectra; the latter region reveals common motifs of vibrational modes for the three molecules for aliphatic CH stretching fundamentals, whereas in the mid-IR region, one is able to identify specific signatures arising from the substituent groups X. In the CH stretching region between 2900 and 2800 cm~(-1), we identify and interpret a group of three IR VCD bands due to HCH bending overtone transitions in Fermi resonance with CH stretching fundamental transitions. The analysis of the NIR region between ~8000 and ~9000 cm~(-1) for X = COOCD3 reveals important features of the aromatic CH stretching overtones that are of value since the aromatic CH stretching fundamentals are almost silent. The intensifying of such overtones is attributed to electrical anharmonicity terms, which are evaluated here by ab initio methods and compared with literature data.
机译：在900〜（-1）范围内的几个区域记录了4-X- [2.2]对环环糊精的两种对映体（X = COOCD3，Cl，I）的振动吸收光谱和振动圆二色性（VCD）光谱。 2000厘米〜（-1）通过与相应光谱的DFT计算比较，对两个IR区900〜（-1）600 cm〜（-1）和2800-3200 cm〜（-1）的VCD光谱进行了分析。后一个区域揭示了脂肪族CH拉伸基本原理的三个分子的振动模态的共同基元，而在中红外区域，一个区域能够识别出由取代基X引起的特定特征。在CH拉伸区域2900和2800之间cm〜（-1），我们识别并解释了一组三个IR VCD波段，这是由于费米共振中的HCH弯曲泛音跃迁和CH拉伸的基本跃迁所致。对X = COOCD3的〜8000和〜9000 cm〜（-1）之间的NIR区域进行分析，揭示了芳族CH拉伸泛音的重要特征，因为芳族CH拉伸基本不言而喻。此类泛音的增强归因于电非谐性项，此处通过从头算方法对其进行评估并与文献数据进行比较。

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