The Study of Vibrational Spectra of 3-Amino-2, 5-Dichlorobenzoic Acid by Density Functional Theory
YANG Shui-jiao1，GAO Ai-hua1*, HU Shang-bin1，HE Xiao-qing1，JIANG Zhen-yi2，CHU San-yang3
1. Department of Physics，Northwestern University，Xi’an 710069，China 2. Institute of Modern Physics，Northwestern University，Xi’an 710069，China 3. Department of Chemistry，Tsinghua University，Hsinchu 30013，Taiwan，China
Abstract：To understand the relationship between the vibrational spectra and the geometry structure of 3-amino-2,5-dichlorobenzoic acid (3A2,5DBA) essentially, geometry optimizations and vibrational frequencies calculation of 3A2, 5DBA were performed at Hartree-Fock (HF) and Becke’s three-parameter hybrid functional (B3) for the exchange part and the Lee-Yang-Parr (LYP) correlation function (B3LYP) level using 6-311G(d, p) basis set, respectively. The structural information and 45-complete normal vibrational modes of 3A2, 5DBA were obtained. Comparing the computational geometric parameters of 3A2,5DBA with the values observed in experimental measurement of benzoic acid as well as the computed vibrational frequencies of 3A2, 5DBA with the reported data of pertinent literature, it was revealed that the results coming from B3LYP/6-311G(d, p) are more reasonable than those by HF/6-311G(d, p). Taking into account the difference between the computed 3A2, 5DBA molecule and the experimental measured sample, the calculated vibrational frequencies were reasonably scaled. Under the B3LYP/6-311G(d, p) method, the scale factor was 1.001 3 for the vibrational frequencies with wave numbers＜800 cm-1, while the scale factor was 0.961 3 for the vibrational frequencies with wave numbers＞800 cm-1. With the help of Gaussian View software package, the theoretically calculated vibrational frequencies were assigned much more accurately. In addition, the vibrational analysis of substitutive groups and main functional groups of 3A2, 5DBA was carried out. Through the comparison of the calculated vibrational frequencies with the frequencies of 3A2, 5DBA observed in FTIR experiment, the authors found that the theoretically calculated vibrational frequencies scaled reasonably were in excellent agreement with the data coming from experimental measurements. Meanwhile, according to the related literature reports, it was shown that our work done in the paper about vibrational assignments and vibrational analysis of 3A2, 5DBA turned out to be reasonable.
Key words：3-amino-2;5-dichlorobenzoic acid;Vibrational frequencies;Density functional theory
杨水蛟1，高爱华1*，胡尚斌1，何小庆1，姜振益2，储三阳3 . 3-氨基-2,5-二氯苯甲酸振动光谱的密度泛函研究 [J]. 光谱学与光谱分析, 2011, 31(07): 1804-1808.
YANG Shui-jiao1，GAO Ai-hua1*, HU Shang-bin1，HE Xiao-qing1，JIANG Zhen-yi2，CHU San-yang3 . The Study of Vibrational Spectra of 3-Amino-2, 5-Dichlorobenzoic Acid by Density Functional Theory . SPECTROSCOPY AND SPECTRAL ANALYSIS, 2011, 31(07): 1804-1808.
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