Vanillin and isovanillin: Comparative vibrational spectroscopic studies, conformational stability and NLO properties by density functional theory calculations

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• 作者：V. Balachandran^a ; ^{brsbala@rediffmail.com} ; K. Parimala^b
• 关键词：FT-IR ; FT-Raman ; DFT ; Vanillin ; Isovanillin ; HOMO&ndash ; LUMO
• 刊名：Spectrochimica Acta Part A ; Molecular and Biomolecular Spectroscopy
• 出版年：2012
• 期刊代码：99_13861425
• 类别：ch
• 出版时间：September, 2012
• 卷：95
• 期：Complete
• 页码：354-368
• 文件大小：1359 K

摘要

This study is a comparative analysis of FT-IR and FT-Raman spectra of vanillin (3-methoxy-4-hydroxybenzaldehyde) and isovanillin (3-hydroxy-4-methoxybenzaldehyde). The molecular structure, vibrational wavenumbers, infrared intensities, Raman scattering activities were calculated for both molecules using the B3LYP density functional theory (DFT) with the standard 6-311++G^鈭椻垪 basis set. The computed values of frequencies are scaled using multiple scaling factors to yield good coherence with the observed values. The calculated harmonic vibrational frequencies are compared with experimental FT-IR and FT-Raman spectra. The geometrical parameters and total energies of vanillin and isovanillin were obtained for all the eight conformers (a-h) from DFT/B3LYP method with 6-311++G^鈭椻垪 basis set. The computational results identified the most stable conformer of vanillin and isovanillin as in the 鈥?em>a鈥?form. Non-linear properties such as electric dipole moment (渭), polarizability (伪), and hyperpolarizability (尾) values of the investigated molecules have been computed using B3LYP quantum chemical calculation. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecules.