Liu Jun-na, Chen Zhi-rong, Yuan Shen-feng
School of Materials Science and Chemical Engineering, Zhejiang University, Hangzhou 310027, China.
J Zhejiang Univ Sci B. 2005 Jun;6(6):584-9. doi: 10.1631/jzus.2005.B0584.
The geometries of azobenzene compounds are optimized with B3LYP/6-311G* method, and analyzed with nature bond orbital, then their visible absorption maxima are calculated with TD-DFT method and ZINDO/S method respectively. The results agree well with the observed values. It was found that for the calculation of visible absorption using ZINDO/S method could rapidly yield better results by adjusting OWF(pi-pi) (the relationship between pi-pi overlap weighting factor) value than by the TD-DFT method. The method of regression showing the linear relationship between OWF(pi-pi) and BL(N-N) (nitrogen-nitrogen bond lengths) as OWF(pi-pi)=-8.1537+6.5638BL(N-N), can be explained in terms of quantum theory, and also be used for prediction of visible absorption maxima of other azobenzne dyes in the same series. This study on molecules' orbital geometry indicates that their visible absorption maxima correspond to the electron transition from HOMO (the highest occupied molecular orbital) to LUMO (the lowest unoccupied molecular orbital).
采用B3LYP/6 - 311G*方法对偶氮苯化合物的几何结构进行优化，并用自然键轨道进行分析，然后分别用TD - DFT方法和ZINDO/S方法计算其可见吸收最大值。结果与观测值吻合良好。研究发现，对于可见吸收的计算，使用ZINDO/S方法通过调整OWF(π - π)（π - π重叠加权因子之间的关系）值比使用TD - DFT方法能更快地得到更好的结果。回归方法表明OWF(π - π)与BL(N - N)（氮 - 氮键长）之间存在线性关系，即OWF(π - π)= - 8.1537 + 6.5638BL(N - N)，这可以用量子理论来解释，也可用于预测同一系列中其他偶氮苯染料的可见吸收最大值。对分子轨道几何结构的这项研究表明，它们的可见吸收最大值对应于从最高占据分子轨道（HOMO）到最低未占据分子轨道（LUMO）的电子跃迁。
