Mizuguchi Jin, Senju Takatoshi
Department of Applied Physics, Graduate School of Engineering, Yokohama National University, 79-5 Tokiwadai, 240-8501 Yokohama, Japan.
J Phys Chem B. 2006 Oct 5;110(39):19154-61. doi: 10.1021/jp060915l.
Quinacridones are industrially important hydrogen-bonded pigments. The color in the solid state is vivid red, while it is pale yellow in solution, indicating evidently the involvement of intermolecular interactions in the solid state. The electronic structure has therefore been investigated with special attention to the role of intermolecular NH...O hydrogen bonds for three representative quinacridone compounds with different hydrogen-bond forming characteristics: unsubstituted gamma-quinacridone (gamma-QA) with two NH groups, mono-N-methylquinacridone (MMQA) with one NH and one CH(3), and N,N'-dimethyl-quinacridone (DMQA) with two CH(3) groups. The number of the NH...O hydrogen bonds per molecule is four, two, and zero for gamma-QA, MMQA, and DMQA, respectively. In solution, no significant difference in absorption maximum is recognized between gamma-QA, MMQA, and DMQA. However, in the solid state, the absorption maximum of gamma-QA appears at the longest wavelength, followed by MMQA and then DMQA, depending on the number of NH...O intermolecular hydrogen bonds. The role of the hydrogen bond is found to align transition dipoles in a "head-to-tail" fashion and to displace the absorption band toward longer wavelengths due to excitonic interactions. The extent of the spectral shift increases with increasing number of hydrogen bonds per molecule.
喹吖啶酮是具有工业重要性的氢键型颜料。其固态颜色为鲜艳的红色，而在溶液中为浅黄色，这明显表明分子间相互作用在固态中起作用。因此，针对三种具有不同氢键形成特性的代表性喹吖啶酮化合物，特别关注分子间NH...O氢键的作用，对其电子结构进行了研究：具有两个NH基团的未取代γ-喹吖啶酮（γ-QA）、具有一个NH和一个CH(3)的单-N-甲基喹吖啶酮（MMQA）以及具有两个CH(3)基团的N,N'-二甲基喹吖啶酮（DMQA）。γ-QA、MMQA和DMQA每分子的NH...O氢键数量分别为四个、两个和零个。在溶液中，γ-QA、MMQA和DMQA之间在最大吸收波长上没有明显差异。然而，在固态中，γ-QA的最大吸收波长出现在最长波长处，其次是MMQA，然后是DMQA，这取决于NH...O分子间氢键的数量。发现氢键的作用是以“头对头”的方式排列跃迁偶极子，并由于激子相互作用使吸收带向更长波长移动。光谱位移的程度随着每分子氢键数量的增加而增大。
