Beaula T Joselin, Packiavathi A, Manimaran D, Joe I Hubert, Rastogi V K, Jothy V Bena
Department of Physics and Research Centre, Women's Christian College, Nagercoil 629 001, Tamil Nadu, India.
Department of Physics and Research Centre, Mar Ivanios College, Nalancira 695015, Kerala, India.
Spectrochim Acta A Mol Biomol Spectrosc. 2015 Mar 5;138:723-35. doi: 10.1016/j.saa.2014.11.034. Epub 2014 Nov 28.
Density Functional Theory (DFT) calculations at B3PW91 level with 6-311G (d) basis sets were carried out for 2,3-Pyrazinedicarboxylic acid (PDCA) to analyze in detail the equilibrium geometries and vibrational spectra. Calculations reveal that the optimized geometry closely resembles the experimental XRD data. Vibrational spectra were analyzed on the basis of potential energy distribution (PED) of each vibrational mode, which provides quantitative as well as qualitative interpretation of IR and Raman spectra. Information about size, shape, charge density distribution and site of chemical reactivity of the molecule were obtained by mapping electron density isosurface with the electrostatic potential surface (ESP). Based on optimized ground state geometries, NBO analysis was performed to study donor-acceptor (bond-antibond) interactions. TD-DFT analysis was also performed to calculate energies, oscillator strength of electronic singlet-singlet transitions and the absorption wavelengths. The (13)C and (1)H nuclear magnetic resonance (NMR) chemical shifts of the molecule in the ground state were calculated by gauge independent atomic orbital (GIAO) method and compared with the experimental values. PDCA was screened for its antimicrobial activity and found to exhibit antifungal and antibacterial effects. Molecular docking was also performed for the different receptors.
采用密度泛函理论（DFT）在B3PW91水平下结合6-311G(d)基组对2,3-吡嗪二甲酸（PDCA）进行计算，以详细分析其平衡几何结构和振动光谱。计算结果表明，优化后的几何结构与实验XRD数据非常相似。基于各振动模式的势能分布（PED）对振动光谱进行分析，这为红外光谱和拉曼光谱提供了定量和定性的解释。通过将电子密度等值面与静电势表面（ESP）映射，获得了有关分子的大小、形状、电荷密度分布和化学反应活性位点的信息。基于优化后的基态几何结构，进行了自然键轨道（NBO）分析以研究给体-受体（键-反键）相互作用。还进行了含时密度泛函理论（TD-DFT）分析以计算电子单重态-单重态跃迁的能量、振子强度和吸收波长。采用规范无关原子轨道（GIAO）方法计算了分子基态的(13)C和(1)H核磁共振（NMR）化学位移，并与实验值进行了比较。对PDCA进行了抗菌活性筛选并发现其具有抗真菌和抗菌作用。还对不同受体进行了分子对接。
