Lasers and Spectroscopy Laboratory, Department of Physics, Banaras Hindu University, Varanasi 221005, India.
Spectrochim Acta A Mol Biomol Spectrosc. 2011 Sep;79(5):1316-25. doi: 10.1016/j.saa.2011.04.062. Epub 2011 May 27.
FTIR and Raman spectra of nicotinic acid and its N-oxide have been recorded and analyzed. The stabilities, optimized molecular geometries, APT charges and vibrational characteristics for the two possible conformers of nicotinic acid and its N-oxide have been computed using DFT method. The E (trans) conformers of both the molecules are found to be more stable and less polar than their respective Z (cis) conformers. Due to addition of an O atom at the N1 site in nicotinic acid the magnitudes of atomic charges on all the H atomic sites of the nicotinic acid N-oxide molecule are found to increase. Most of the vibrational frequencies have nearly the same magnitude for the two conformers of both the molecules. However, significant changes are noticed in their IR intensities, Raman activities and depolarization ratios of the Raman bands. The calculated frequencies have been correlated with the experimental frequencies.
已记录和分析了烟酸及其 N-氧化物的傅里叶变换红外（FTIR）和拉曼光谱。使用密度泛函理论（DFT）方法计算了两种可能构象的烟酸及其 N-氧化物的稳定性、优化的分子几何形状、APT 电荷和振动特性。发现两种分子的 E（反式）构象比相应的 Z（顺式）构象更稳定、极性更小。由于在烟酸的 N1 位添加了一个 O 原子，烟酸 N-氧化物分子中所有 H 原子位置的原子电荷数值都增大。对于两种分子的两个构象，大多数振动频率的大小几乎相同。然而，在它们的红外强度、拉曼活性和拉曼带的退偏比方面，有明显的变化。计算出的频率与实验频率相关联。
