Preat Julien, Jacquemin Denis, Wathelet Valérie, André Jean-Marie, Perpète Eric A
Laboratoire de Chimie Théorique Appliquée, Facultés Universitaires Notre-Dame de la Paix, 61 Rue de Bruxelles, 5000 Namur, Belgium.
J Phys Chem A. 2006 Jul 6;110(26):8144-50. doi: 10.1021/jp061260r.
The UV absorption spectra of more than 80 substituted coumarins and chromones have been investigated with the PCM-TD-DFT theoretical scheme using three hybrid functionals (O3LYP, B3LYP, and PBE0) and taking into account methanol or ethanol solvation effects. For most of the studied derivatives, there are at least two allowed excited states presenting a strong oscillator strength in the UV region. The first allowed excitation is associated to a HOMO-LUMO transition whereas the second corresponds to a transition from the HOMO-1 to the LUMO. Both involve a charge transfer from the benzenic cycle to the pyranone moiety. Statistically treating the PBE0 results allows a prediction of the lambda(max) with small standard deviations: in methanol, 6 nm (0.07 eV) for the first excitation (lambda(max)(1)) and 5 nm (0.08 eV) for the second one (lambda(max)(2)), whereas in ethanol 6 nm (0.08 eV) for (lambda(max)(1)) and 6 nm (0.13 eV) for (lambda(max)(2)).
使用三种杂化泛函（O3LYP、B3LYP和PBE0）并考虑甲醇或乙醇溶剂化效应，通过PCM-TD-DFT理论方案研究了80多种取代香豆素和色酮的紫外吸收光谱。对于大多数研究的衍生物，在紫外区域至少有两个允许的激发态呈现出很强的振子强度。第一个允许的激发与HOMO-LUMO跃迁相关，而第二个对应于从HOMO-1到LUMO的跃迁。两者都涉及从苯环到吡喃酮部分的电荷转移。对PBE0结果进行统计处理，可以预测出标准偏差较小的λ(max)：在甲醇中，第一次激发（λ(max)(1)）为6nm（0.07eV），第二次激发（λ(max)(2)）为5nm（0.08eV）；而在乙醇中，（λ(max)(1)）为6nm（0.08eV），（λ(max)(2)）为6nm（0.13eV）。
