银松素类衍生物分子的几何结构和光谱性质

Spectroscopic Properties of Pinosylvin by Density Functional Theory

采用密度泛函理论（Density functional theory，DFT）方法研究了7个银松素衍生物分子的结构和光谱性质。在B3LYP／6—311G＊＊理论级别上优化了它们的几何结构，通过频率计算拟合了分子的红外振动光谱：具有共轭芳烃特征的银松素衍生物体系在1650—1450cm^-1具有高红外活性的苯环伸缩振动峰，而双键在1690cm^-1附近的特征伸缩振动是偶级对称振动，不产生高强度红外光谱吸收峰；在高频区（3830cm^-1）观察到羟基的O—H键伸缩振动谱带。采用含时密度泛函理论（Time-dependent Density functional theory，TD—DFT）方法和极化连续介质模型（Polarized Continuum Model，PCM）计算了上述分子在CHCl3溶液中的电子吸收光谱，计算揭示吸收谱带以π→π＊跃迁为主，羟基和甲氧基的引入仅起修饰作用。

Structural and spectroscopic properties of pinosylvin and its derivatives at the density functional theory （DFT） level were explored. The structures were optimized by the B3LYP method with the basis sets of 6-311G ^＊＊. Experimental infrared spectra were well reproduced by the theoretically simulated vibration spectra. The bands of 1 650 - 1 450 cm^-1, 1 690 and 3 830 cm^-1 are attributed to the featured variations of phenyl ring, C = C bond and O-H bond, respectively. Among these, the C = C stretching vibration belongs to a dipole-forbidden vibration, difficultly observed in the experimental infrared spectra. On the basis of the optimized structures, calculations with time-dependent density functional theory （TD- DFT） and polarized continuum model （PCM） were performed to predict the absorption spectra of the title molecules in the CHCl3 solution, which reveals that the π→π ＊ transitions are dominant in the absorption bands, modified by the -OH and -OCH3 groups when they are introduced into the parent molecule.