Photonics Division, School of Advanced Sciences, VIT University, Vellore, Tamilnadu, India.
Spectrochim Acta A Mol Biomol Spectrosc. 2011 Dec;83(1):478-89. doi: 10.1016/j.saa.2011.08.069. Epub 2011 Sep 8.
The Fourier Transform Infrared (FT-IR) and Fourier Transform Raman (FT-Raman) spectra of antiepileptic drug Ethosuximide (ETX) have been recorded and analyzed. In addition, the IR spectra in CCl(4) at various concentrations of ETX are also recorded. The equilibrium geometry, bonding features and harmonic vibrational frequencies have been investigated with the help of Density Functional Theory (DFT) method. The (1)H and (13)C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by the Gauge Including Atomic Orbital (GIAO) method. Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The results show that charge in electron density (ED) in the σ* and π* antibonding orbitals and second order delocalization energies E(2) confirms the occurrence of intramolecular charge transfer (ICT) within the molecule. UV-vis spectrum of the compound was recorded and the electronic properties, such as HOMO and LUMO energies, were performed by Time-Dependent Density Functional Theory (TD-DFT) approach. Finally the calculation results were applied to simulate infrared and Raman spectra of the title compound which showed good agreement with observed spectra.
已记录和分析了抗癫痫药物乙琥胺（ETX）的傅里叶变换红外（FT-IR）和傅里叶变换拉曼（FT-Raman）光谱。此外，还记录了 ETX 在不同浓度的 CCl(4)中的红外光谱。借助密度泛函理论（DFT）方法研究了平衡几何形状、键合特征和谐振动频率。通过规范包含原子轨道（GIAO）方法计算了分子的（1）H 和（13）C 核磁共振（NMR）化学位移。使用自然键轨道（NBO）分析分析了超共轭相互作用和电荷离域引起的分子稳定性。结果表明，在 σ和π反键轨道中的电子密度（ED）中的电荷和二阶离域能 E(2)证实了分子内电荷转移（ICT）的发生。记录了化合物的紫外-可见光谱，并通过时间相关密度泛函理论（TD-DFT）方法进行了 HOMO 和 LUMO 能量等电子性质的计算。最后，将计算结果应用于模拟标题化合物的红外和拉曼光谱，结果与观察到的光谱吻合良好。
