Longhi Giovanna, Abbate Sergio, Gangemi Roberto, Giorgio Egidio, Rosini Carlo
Dipartimento di Scienze Biomediche e Biotecnologie, Università di Brescia, viale Europa 11, 25123 Brescia, Italy.
J Phys Chem A. 2006 Apr 20;110(15):4958-68. doi: 10.1021/jp057178y.
We report and discuss the infrared (IR) vibrational circular dichroism (VCD) spectra of the enantiomeric pairs of the olefin derivatives of fenchone (1,3,3-trimethyl-2-methylenebicyclo[2.2.1]heptane) and camphor (1,7,7-trimethyl-2-methylenebicyclo[2.2.1]heptane), respectively, together with those of the parent molecules. The VCD spectra were taken in three spectral regions: the mid-IR region, encompassing the fundamental deformation modes, the region of CH-stretching fundamental modes and the NIR-region between 1100 and 1300 nm, which corresponds to the second CH-stretching overtone. The VCD and absorption spectra in the first two regions are analyzed by use of current density functional theory (DFT) calculations. The NIR region is analyzed by a protocol that consists of the use of DFT-based calculations and in assuming local mode behavior: the local mode approach is found appropriate for interpreting the absorption spectra and, for the moment, acceptable for calculating NIR-VCD spectra. The analysis of the first region allows us to track the contribution of the C=O group in the vibrational optical activity of C-C stretching modes; notable differences are indeed found in olefins and ketones. On the contrary, in the other two regions the VCD spectra of olefins and ketones are more similar: in the normal mode region of CH stretching fundamentals the spectra are determined by the mutual orientation of the CH bonds; in the second overtone local mode region olefins and ketones signals show some differences.
我们分别报告并讨论了葑酮（1,3,3-三甲基-2-亚甲基双环[2.2.1]庚烷）和樟脑（1,7,7-三甲基-2-亚甲基双环[2.2.1]庚烷）的烯烃衍生物对映体对的红外（IR）振动圆二色性（VCD）光谱，以及母体分子的相应光谱。VCD光谱在三个光谱区域采集：中红外区域，涵盖基本变形模式；CH伸缩基本模式区域；以及1100至1300nm的近红外区域，该区域对应于第二个CH伸缩泛频。前两个区域的VCD光谱和吸收光谱通过使用当前密度泛函理论（DFT）计算进行分析。近红外区域通过一种协议进行分析，该协议包括使用基于DFT的计算并假设局部模式行为：发现局部模式方法适用于解释吸收光谱，并且目前对于计算近红外VCD光谱是可接受的。对第一个区域的分析使我们能够追踪C=O基团在C-C伸缩模式的振动光学活性中的贡献；确实在烯烃和酮中发现了显著差异。相反，在其他两个区域中，烯烃和酮的VCD光谱更为相似：在CH伸缩基本模式的正常模式区域，光谱由CH键的相互取向决定；在第二个泛频局部模式区域，烯烃和酮的信号显示出一些差异。
