吡啶酮系偶氮类化合物可见吸收光谱的预测

利用密度泛函的B3LYP方法, 在6-311G*基组水平对吡啶酮系偶氮类化合物进行构型优化, 并进行了自然键轨道(NBO)分析, 然后用TDDFT方法和ZINDO/S方法分别计算了它们的可见吸收光谱, 结果均与实验值十分吻合. 通过对比发现, 对于最高吸收波长的计算, ZINDO/S能以较快的速度得到较好的结果. 在用ZINDO/S计算的过程中, 回归分析发现π-π重叠加权因子(OWF_π-π)与染料分子吡啶环上两个羰基氧原子平均电荷Z_O有较好的线性关系: OWF_π-π＝0.11425－1.04178ZO, 这一关系不仅可从量子化学的角度进行解释, 而且可用于同类染料可见吸收光谱的预测. 分子轨道的研究表明, 这些化合物的最高可见吸收波长主要对应着共轭体系中给电子体到受电子体的电子跃迁.

Prediction of Visible Absorption of Pyridone Azo Compounds

Based on B3LYP method of DFT, the geometry of pyridone azo compounds was optimized at the level of 6-311G* basis, and analyzed by NBO (nature bond orbital) method. Their visible absorption maxima were calculated with TDDFT method and ZINDO/S method, the results agreed with the observed values excellently. It was shown that the visible absorption maxima can be calculated more precisely in much shorter time with ZINDO/S method by adjusting that the value of π-π overlap weighting factor (OWF_π-π) than TDDFT method. In the process of calculation with ZINDO/S, in virtue of the method of regression it was found that the linear relationship between OWF_π-π and Z_O(the average net charge on oxygen of the two carbonyl-groups in pyridone) was excellent, OWF_π-π＝0.11425－1.04718Z_O, that is, with the drop of Z_O, OWF_π-π increased. The relationship not only could be explained in terms of quantum theory, but also could be used to predict the visible absorption maxima of other pyridone azo compounds in the same series. What′s more, the study on molecular orbital implied that the electron transition from the electron donators to electron acceptors of conjugate system resulted in their visible absorption maxima.