Department of Chemistry, Institute of Science, Banaras Hindu University, Varanasi 221005, India.
Department of Chemistry, Faculty of Science, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, Japan.
Spectrochim Acta A Mol Biomol Spectrosc. 2020 Jan 5;224:117419. doi: 10.1016/j.saa.2019.117419. Epub 2019 Jul 24.
The Raman spectra of a series of synthesized DC molecules (benzylidene malononitrile derivatives) with different electron donating (EDG) and electron withdrawing (EWG) group have been presented and analyzed with DFT calculated spectra. In particular, different functional groups effect on cyano stretching (∼2200 cm), phenyl ring breathing and alkenic double bond stretch which often appears mixed up (1475-1650 cm) are studied systematically for several aromatic conjugated DC derivatives. Interestingly, symmetric stretching frequency of the DC compounds having two CN groups at geminal position appears at higher wavenumber (by 11-15 cm) compared to their corresponding asymmetric stretch frequency. Angle (between dicyano group) dependent theoretical study indicates that the relative appearance of cyano symmetric/anti-symmetric stretching frequency depends on whether dicyano groups are at the geminal or vicinal position and the angle between them. Complete band assignments of observed Raman frequencies have been performed by potential energy distributions (PEDs) available in GAR2PED software. Our results will help to understand the vibrational feature of this important class of compounds in biological medium when used as probe.
本文呈现了一系列具有不同供电子（EDG）和吸电子（EWG）基团的合成 DC 分子（亚苄基丙二腈衍生物）的拉曼光谱，并结合 DFT 计算光谱进行了分析。特别地，研究了不同官能团对氰基伸缩（~2200cm）、苯环呼吸和烯键伸缩的影响，这些伸缩通常会混合在一起（1475-1650cm），对几个芳香共轭 DC 衍生物进行了系统研究。有趣的是，具有两个位于偕位 CN 基团的 DC 化合物的对称伸缩频率出现在较高的波数（高 11-15cm），而其对应的不对称伸缩频率较低。角（两个氰基基团之间）相关的理论研究表明，氰基对称/反对称伸缩频率的相对出现取决于两个氰基基团是位于偕位还是邻位，以及它们之间的角度。通过 GAR2PED 软件中提供的势能分布（PED），对观察到的拉曼频率的完整带分配进行了执行。当用作探针时，我们的结果将有助于理解此类重要化合物在生物介质中的振动特征。
