Department of Physics, A.A. Govt. Arts College, Musiri 621 211, Tamil Nadu, India.
Spectrochim Acta A Mol Biomol Spectrosc. 2013 Mar;104:451-60. doi: 10.1016/j.saa.2012.11.057. Epub 2012 Nov 29.
The FT-IR and FT-Raman vibrational spectra of ninhydrin have been recorded in the range 4000-400 cm(-1)and 3600-50 cm(-1), respectively. A detailed vibrational spectral analysis has been carried out and assignments of the observed fundamental bands have been proposed on the basis of peak positions and relative intensities. The optimized molecular geometry, vibrational frequencies, atomic charges, dipole moment, rotational constants and several thermodynamic parameters in the ground state are calculated using ab initio HF and density functional B3LYP methods with 6-311++G(d,p) basis set combination. In order to find the most optimized geometry, the energy calculations are carried out for various possible conformers. Keto and enol forms of ninhydrin are also studied. The condensed summary of the principal NBOs shows the occupancy, orbital energy and the qualitative pattern of delocalization interactions of ninhydrin. The calculated HOMO-LUMO energies reveal that charge transfer occurs within the molecule. The predicted first hyperpolarizability also shows that the ninhydrin molecule have good optical quality and nonlinear optical (NLO) behavior. With the help of specific scaling procedures, the observed vibrational wave numbers in FT-IR and FT-Raman spectra are analyzed and assigned to different normal modes of the molecule.
本文记录了邻苯二醛的 FT-IR 和 FT-Raman 振动光谱，范围分别为 4000-400 cm(-1) 和 3600-50 cm(-1)。通过峰位置和相对强度，进行了详细的振动光谱分析，并提出了观察到的基本谱带的分配。使用 HF 和 B3LYP 密度泛函方法，在 6-311++G(d,p)基组组合上，计算了优化的分子几何形状、振动频率、原子电荷、偶极矩、转动常数和基态下的几个热力学参数。为了找到最优化的几何形状，对各种可能的构象进行了能量计算。本文还研究了邻苯二醛的酮式和烯醇式。邻苯二醛的主要 NBO 的简要总结显示了占据、轨道能量和离域相互作用的定性模式。计算的 HOMO-LUMO 能量表明电荷转移发生在分子内。预测的第一超极化率也表明邻苯二醛分子具有良好的光学质量和非线性光学（NLO）行为。借助特定的缩放程序，对 FT-IR 和 FT-Raman 光谱中的观察到的振动波数进行了分析，并分配到分子的不同正则模式。
