Prasad M V S, Udaya Sri N, Veeraiah V
Department of Physics, D.N.R. College, Bhimavaram, W.G. Dt, Andhra Pradesh 534202, India.
Department of Physics, D.N.R. College, Bhimavaram, W.G. Dt, Andhra Pradesh 534202, India.
Spectrochim Acta A Mol Biomol Spectrosc. 2015 Sep 5;148:163-74. doi: 10.1016/j.saa.2015.03.105. Epub 2015 Apr 7.
In the present study, the FT-IR and FT-Raman spectra of 2-chloro-3-quinolinecarboxaldehyde (2Cl3QC) have been recorded in the region 4000-400 and 3500-50 cm(-1), respectively. The fundamental modes of vibrational frequencies of 2Cl3QC are assigned. Theoretical information on the optimized geometry, harmonic vibrational frequencies, infrared and Raman intensities were obtained by means of density functional theory (DFT) gradient calculations with complete relaxation in the potential energy surface using 6-31G(d,p) basis set. The vibrational frequencies which were determined experimentally from the spectral data are compared with those obtained theoretically from DFT calculations. A close agreement was achieved between the observed and calculated frequencies by refinement of the scale factors. The infrared and Raman spectra were also predicted from the calculated intensities. Thermodynamic properties like entropy, heat capacity, zero point energy, have been calculated for the molecule. The predicted first hyperpolarizability also shows that the molecule might have a reasonably good non-linear optical (NLO) behavior. The calculated HOMO-LUMO energy gap reveals that charge transfer occurs within the molecule. Stability of the molecule arising from hyper conjugative interactions, charge delocalization have been analyzed using natural bond orbitals (NBO) analysis. The results show that charge in electron density (ED) in the π(∗) antibonding orbitals and E((2)) energies confirms the occurrence of ICT (intra-molecular charge transfer) within the molecule. UV-visible spectrum of the title molecule has also been calculated using TD-DFT/CAM-B3LYP/6-31G(d,p) method. The calculated energy and oscillator strength almost exactly reproduces reported experimental data.
在本研究中，分别在4000 - 400 cm⁻¹和3500 - 50 cm⁻¹区域记录了2 - 氯 - 3 - 喹啉甲醛（2Cl3QC）的傅里叶变换红外光谱（FT - IR）和傅里叶变换拉曼光谱（FT - Raman）。对2Cl3QC的基本振动频率模式进行了归属。通过使用6 - 31G(d,p)基组在势能面进行完全弛豫的密度泛函理论（DFT）梯度计算，获得了关于优化几何结构、简谐振动频率、红外和拉曼强度的理论信息。将从光谱数据实验测定的振动频率与从DFT计算理论获得的频率进行比较。通过对比例因子的优化，观测频率与计算频率之间达成了紧密一致。还根据计算强度预测了红外和拉曼光谱。计算了该分子的热力学性质，如熵、热容、零点能。预测的第一超极化率还表明该分子可能具有相当良好的非线性光学（NLO）行为。计算的最高占据分子轨道（HOMO） - 最低未占据分子轨道（LUMO）能隙表明分子内发生了电荷转移。使用自然键轨道（NBO）分析对由超共轭相互作用和电荷离域引起的分子稳定性进行了分析。结果表明，π(∗)反键轨道中的电子密度（ED）电荷和E((2))能量证实了分子内发生了分子内电荷转移（ICT）。还使用TD - DFT/CAM - B3LYP/6 - 31G(d,p)方法计算了标题分子的紫外可见光谱。计算的能量和振子强度几乎精确地重现了报道的实验数据。
