Jacquemin Denis, Preat Julien, Wathelet Valérie, Fontaine Michèle, Perpète Eric A
Laboratoire de Chimie Théorique Appliquée, Facultés Universitaires Notre-Dame de la Paix, rue de Bruxelles 61, B-5000 Namur, Belgium.
J Am Chem Soc. 2006 Feb 15;128(6):2072-83. doi: 10.1021/ja056676h.
The structure and visible spectra of a large panel of thioindigo dyes and derivatives have been evaluated using a TD-PBE0/6-311+G(2d,p)//PBE0/6-311G(d,p) approach explicitly taking bulk solvent effects into account by means of the polarizable continuum model. The influence of the solvent characteristics, the trans-cis isomerization, and the chemical substitution on the benzene rings have been investigated. In addition, hemi-thioindigo dyes, thiazine-indigo, chromophore-like molecules, and selenoindigo have been considered. Though the relative oscillator strengths of the two allowed visible transitions in the nonplanar cis isomers are not always correctly reproduced by theory, the agreement between theoretical and experimental results is far above expectations. For the 170 cases studied, we obtained a mean unsigned error on the predicted lambda(max) limited to 6.9 nm or 0.03 eV, with only 6 (4) cases for which the difference exceeds 20 nm (0.10 eV). These errors are 1 order of magnitude smaller than what has previously been reported for indigoids. A linear correlation between the central double bond length and the lambda(max) has been established, while the bond length and vibrational frequency of the carbonyl groups do not correlate with the thioindigo color. The higher excitation energies of the cis conformers, compared to the trans structures, result from a less stabilized LUMO in the former case. Indeed, for cis thioindigo, the two electron-rich (in the excited state) carbonyl units lie close to each other.
使用TD-PBE0/6-311+G(2d,p)//PBE0/6-311G(d,p)方法，通过极化连续介质模型明确考虑本体溶剂效应，对一大组硫靛染料及其衍生物的结构和可见光谱进行了评估。研究了溶剂特性、反式-顺式异构化以及苯环上的化学取代的影响。此外，还考虑了半硫靛染料、噻嗪-靛蓝、类发色团分子和硒靛。尽管理论上并不总是能正确再现非平面顺式异构体中两个允许的可见跃迁的相对振子强度，但理论结果与实验结果之间的一致性远远超出预期。对于所研究的170个案例，我们在预测的λ(max)上获得的平均绝对误差限制在6.9 nm或0.03 eV以内，只有6（4）个案例的差异超过20 nm（0.10 eV）。这些误差比之前报道的靛族化合物的误差小1个数量级。已建立中心双键长度与λ(max)之间的线性相关性，而羰基的键长和振动频率与硫靛颜色无关。与反式结构相比，顺式构象体具有更高的激发能，这是因为前者的最低未占分子轨道（LUMO）稳定性较低。实际上，对于顺式硫靛，两个富电子（在激发态）的羰基单元彼此靠近。
