Department of Nanoscience, Faculty of Engineering, Sojo University, 4-22-1 Ikeda, Kumamoto 860-0082, Japan.
Chemistry. 2010 Mar 22;16(12):3676-89. doi: 10.1002/chem.200902936.
An organogelator (G) that contains 2-anthracenecarboxylic acid (2Ac) attached covalently to a gelator counterpart that consists of 3,4,5-tris(n-dodecan-1-yloxy)benzoic acid by means of a chiral amino alcohol linkage has been synthesized. G acts as an efficient gelator of organic solvents, including mixed solvents and chiral solvents. Photodimers isolated after the photoreaction of the gel samples display different degrees of stereoselectivity. In the gel state, the formation of head-to-head (h-h) photodimers is always favored over head-to-tail (h-t) photodimers. Enantiomeric excess (ee) values of the major h-h photodimers reached as high as -56% in the case of the gels with enantiomeric glycidyl methyl ethers. Here, the solvent chirality is outweighed by the intrinsic chirality of the gelator molecule. The packing of the chromophore in the gel state has been characterized by the absorption and the emission behaviors and their variations during the course of gel-to-sol phase transition. Whereas for the hexane gel, emission intensity increases with an increase in temperature, other systems show a decrease in emission intensity. Redshift of the lambda(max) in the gel spectra indicates the J-aggregate arrangement of the chromophores. Chiral transcription in the gel state has been investigated by CD spectroscopy, which shows a decrease in CD intensity during the gel-to-sol phase transition. The X-ray diffraction study clearly differentiates among the gels in terms of the order of molecular arrangements. The gel systems are categorized as strong, moderately strong, and weak, that originate from the cooperative or individual participations of intermolecular hydrogen-bonding and pi-pi interactions, fine-tuned by the solvent polarity and the gelation temperature. A simple model based on the experimental findings and the molecular preorientation as evidenced by the stereochemistry of the photodimers has been proposed.
已合成了一种含有共价连接的 2-蒽羧酸（2Ac）的有机凝胶剂（G），该凝胶剂由 3,4,5-三（正十二烷-1-氧基）苯甲酸和手性氨基醇键组成。G 是有机溶剂的有效凝胶剂，包括混合溶剂和手性溶剂。凝胶样品的光反应后分离出的光二聚体显示出不同程度的立体选择性。在凝胶状态下，头对头（h-h）光二聚体的形成总是优先于头对尾（h-t）光二聚体。在手性缩水甘油甲醚凝胶中，主要 h-h 光二聚体的对映体过量（ee）值高达-56%。在这里，溶剂手性被凝胶剂分子的固有手性所超越。通过吸收和发射行为及其在凝胶-溶胶相转变过程中的变化，对凝胶状态下发色团的组装进行了表征。对于己烷凝胶，发射强度随温度升高而增加，而其他体系则发射强度降低。凝胶光谱中 lambda(max)的红移表明发色团的 J-聚集体排列。通过圆二色光谱研究了凝胶状态下的手性转录，其在凝胶-溶胶相转变过程中显示出 CD 强度的降低。X 射线衍射研究清楚地区分了不同的凝胶，这取决于分子排列的有序性。凝胶体系分为强、中强和弱，这源于分子间氢键和 pi-pi 相互作用的协同或单独参与，通过溶剂极性和凝胶化温度进行微调。提出了一种基于实验结果和由光二聚体的立体化学证明的分子预取向的简单模型。
