红外光谱是化合物结构鉴定的重要信息来源, 对天然有机药物的分子结构及其生物活性研究意义重大。 而随着理论计算方法更加合理、 计算精度不断提高, 理论计算在红外光谱模拟、 振动模式归属指认等方面优势更加明显, 对红外光谱解析等实验研究具有重要参考价值。 本研究利用密度泛函理论(density functional theory, DFT)/B3LYP方法, 在6-311G(d,p)基组水平对7-羟基香豆素进行了几何结构优化和红外光谱计算, 得到稳定结构及全部振动模式。 计算结果显示7-羟基香豆素红外光谱吸收峰主要分布于波数3 700～3 500, 3 150～3 000, 1 750～1 400, 1 400～1 000, 1 000～50 cm-1几个区域。 除波数3 700～3 500, 3 150～3 000 cm-1范围内振动相对独立, 分别归属为O—H伸缩振动和芳环C—H伸缩振动外, 其他几个区域均较为复杂, 谱峰不同程度由多个振动模式叠加而成。 最后, 根据振动模式理论及振动图像分析, 对所有振动模式进行了详细指认。 并通过线性回归方法, 利用相关系数值r研究了7-羟基香豆素红外光谱主要吸收峰波数理论计算值和实验数据的相关性。 结果表明, 计算值和实验值基本吻合, 相关系数值等于0.998 5, 相关性较好; 采用密度泛函理论在该基组水平对7-羟基香豆素红外光谱的理论计算较为可靠。

Infrared spectroscopy is an important source of information for the identification of the compounds structure and it is great significant for biological activity research of natural and organic drug molecules. With the theoretical calculation method is more reasonable and calculation accuracy continues to improve, Theoretical calculate advantage is more obvious in the infrared spectrum simulation and vibration modes attributable identified. And it has important reference value for experimental study of infrared spectral analysis. Using density functional theory, geometry optimizations and frequencies calculation of 7-Hydroxycoumarin were performed at the level of B3LYP/6-311G(d,p), the stable structure and all vibration modes of 7-Hydroxycoumarin were attained. The results show that the infrared absorption peak of 7-hydroxycoumarin is mainly distributed in the several regions in wave number of 3 700～3 500, 3 150～3 000, 1 750～1 400, 1 400～1 000, 1 000～50 cm-1. In addition to the vibration in a wave number range of 3 700～3 500, 3 150～3 000 cm-1 is relatively independent, and were attributed to OH stretching vibration and benzene ring CH stretching vibration, the other several vibration regions are more complex, the different degree of spectral peaks is composed of multiple vibration modes. Finally, based on the theoretical analysis of the vibration mode, the vibration modes of 7-Hydroxycoumarin molecule were assigned, and in order to discuss the reliability of theoretical calculation method, the correlation diagram of the main absorption peak of 7-hydroxyl group was drawn from the theoretical value of X axis and the experimental value of Y axis, the correlation between experimental IR data and calculated IR data of 7-Hydroxycoumarin was analyzed through the linear regression method. Results show that they have good correlation, correlation coefficient values “r” equals 0.998 5, and the theory calculation of 7-Hydroxycoumarin IR by density functional theory at the base set level is reliable.