Snehalatha M, Ravikumar C, Hubert Joe I, Sekar N, Jayakumar V S
Center for Molecular and Biophysics Research, Department of Physics, Mar Ivanios College, Thiruvananthapuram, 695015 Kerala, India.
Spectrochim Acta A Mol Biomol Spectrosc. 2009 Apr;72(3):654-62. doi: 10.1016/j.saa.2008.11.017. Epub 2008 Nov 24.
FT-IR and Raman techniques were employed for the vibrational characterization of the food additive Carmoisine (E122). The equilibrium geometry, various bonding features, and harmonic vibrational wavenumbers have been investigated with the help of density functional theory (DFT) calculations. A good correlation was found between the computed and experimental wavenumbers. Azo stretching wavenumbers have been lowered due to conjugation and pi-electron delocalization. Predicted electronic absorption spectra from TD-DFT calculation have been analysed comparing with the UV-vis spectrum. The first hyperpolarizability of the molecule is calculated. Intramolecular charge transfer (ICT) responsible for the optical nonlinearity of the dye molecule has been discussed theoretically and experimentally. Stability of the molecule arising from hyperconjugative interactions, charge delocalization and C-H ...O, improper, blue shifted hydrogen bonds have been analysed using natural bond orbital (NBO) analysis.
傅里叶变换红外光谱（FT-IR）和拉曼光谱技术被用于食品添加剂胭脂红（E122）的振动特性表征。借助密度泛函理论（DFT）计算研究了其平衡几何结构、各种键合特征和谐波振动波数。计算得到的波数与实验波数之间存在良好的相关性。由于共轭和π电子离域，偶氮伸缩波数降低。将含时密度泛函理论（TD-DFT）计算预测的电子吸收光谱与紫外可见光谱进行了比较分析。计算了该分子的第一超极化率。从理论和实验两方面讨论了导致染料分子光学非线性的分子内电荷转移（ICT）。使用自然键轨道（NBO）分析方法分析了由超共轭相互作用、电荷离域以及C-H…O、不规则、蓝移氢键所产生的分子稳定性。
