Studies on a new class of organogelator containing 2-anthracenecarboxylic acid: influence of gelator and solvent on stereochemistry of the photodimers.
Studies on a new class of organogelator containing 2-anthracenecarboxylic acid: influence of gelator and solvent on stereochemistry of the photodimers.
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DOI：
10.1039/b910741j
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发表时间：
2009-10
影响因子：
3.2
通讯作者：
A. Dawn;Norifumi Fujita;Shuichi Haraguchi;K. Sada;S. Tamaru;S. Shinkai
中科院分区：
文献类型：
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作者：
A. Dawn;Norifumi Fujita;Shuichi Haraguchi;K. Sada;S. Tamaru;S. Shinkai
以2-蒽甲酸（2Ac）为骨架，与3，4，5-三（正十二烷氧基）苯甲酰胺（3，4，5-tris（n-dodecoxy）benzoylamide）形成非共价键，合成了一类新的二元有机胶凝剂（G1，G2和G3）。在这三种胶凝因子中，两种（G2和G3）是分别含有D-丙氨酸或L-2-苯基甘氨酸部分的手性胶凝因子。它们可以作为具有不同极性的有机溶剂的有效胶凝剂，这取决于胶凝剂系统。凝胶因子G1甚至可以凝胶化手性溶剂。凝胶样品的光照射产生对不同体系具有不同立体选择性程度的光环二聚体。具有G1和G2的凝胶产生头对头（h-h）光二聚体作为主要产物，而具有G3的凝胶产生头对头尾（h-t）光二聚体作为主要产物的立体选择性相反。其中，G2/环己烷凝胶显示出最高程度的立体选择性，仅产生具有一些显著量的手性诱导的h-h光二聚体。其他手性系统表现出低到中等的手性诱导。凝胶因子G1可以通过表现出不同的凝胶熔化温度（T（gel））来区分溶剂的外消旋和对映体纯的种类。对于不同的凝胶系统，T（凝胶）增加，在所有的情况下，作为光反应的结果，除了G2/环己烷凝胶，其中一个突出的凝胶到溶胶的相变过程中可以观察到的光反应。氢键和π-π堆积相互作用在构建凝胶结构中起主要作用。凝胶系统的形态在一维原纤和原纤网络结构之间变化。此外，还研究了凝胶因子和溶剂极性对光反应速率、光产物分布以及凝胶结构的影响。
A new class of binary organogelator (G1, G2 and G3) based on 2-anthracenecarboxylic acid (2Ac), attached noncovalently with the gelator counterpart containing a 3,4,5-tris(n-dodecyloxy)benzoylamide backbone has been developed. Among the three gelators, two (G2 and G3) are chiral containing D-alanine or L-2-phenylglycine moieties, respectively. They can act as efficient gelators of organic solvents with varying polarity depending upon the gelator systems. Gelator G1 even gelates chiral solvents. The photoirradiation of the gel samples produces photocyclodimers having different degrees of stereoselectivity for different systems. Gels with G1 and G2 produce head-to-head (h-h) photodimers as major products, whereas the stereoselectivity is reversed for the gels with G3 producing head-to-tail (h-t) photodimers as major products. Among those, G2/cyclohexane gel shows the highest degree of stereoselectivity, producing only h-h photodimers with some significant amount of chiral induction. Other chiral systems exhibit low to moderate chiral inductions. The gelator G1 can differentiate between the racemic and enantiomerically pure varieties of a solvent by exhibiting different gel melting temperatures (T(gel)). For different gel systems, T(gel) increases in all the cases as a consequence of photoreaction, except for the G2/cyclohexane gel, where a prominent gel-to-sol phase transition can be observed during the photoreaction. Hydrogen-bonding and pi-pi stacking interactions play the principal roles in constructing the gel structure. The morphologies of the gel systems vary between one-dimensional fibrils and a fibrillar network structure. In addition, the influences of the gelator and solvent polarity on the rate of photoreactions, photoproduct distributions as well as gel structures are investigated.