Beijing National Laboratory for Molecular Science, CAS Key Laboratory of Colloid, Interface and Chemical Thermodynamics, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, P. R. China.
University of Chinese Academy of Sciences , Beijing 100049, P. R. China.
Langmuir. 2017 Oct 31;33(43):12419-12426. doi: 10.1021/acs.langmuir.7b02285. Epub 2017 Oct 17.
Binary supramolecular gels based on achiral azobenzene derivatives and a chiral chaperone gelator, long-alkyl-chain-substituted L-Histidine (abbreviated as LHC18) that could assist many nongelling acids in forming gels, were investigated in order to fabricate the chiroptical gel materials in a simple way. It was found that although the carboxylic acid-terminated achiral azobenzene derivatives could not form gels in any solvents, when mixed with LHC18 they formed the co-gels and self-assembled into various morphologies ranging from nanotubes and loose nanotubes to nanosheets, depending on the substituent groups on the azobenzene moiety. The ether linkage and the number of carboxylic acid groups attached to the azobenzene moiety played important roles. Upon gel formation, the localized molecular chirality in LHC18 could be transferred to the azobenzene moiety. Combined with the trans-cis isomerization of the azobenzene, optically and chiroptically reversible gels were generated. It was found that the gel based on azobenzene with two carboxylic acid groups and ether linkages showed clear optical reversibility but less chiroptical reversibility, whereas the gel based on azobenzene with one carboxylic acid and an ether linkage showed both optical and chiroptical reversibility. Thus, new insights into the relationship among the molecular structures of the azobenzene, self-assembled nanostructures in the gel and the optical and chiroptical reversibility were disclosed.
基于手性介晶和非手性偶氮苯衍生物的双超分子凝胶，长链取代 L-组氨酸（缩写为 LHC18），能够辅助许多非凝胶酸形成凝胶，被用于研究，以简单的方式制备手性凝胶材料。研究发现，虽然羧酸端基非手性偶氮苯衍生物在任何溶剂中都不能形成凝胶，但与 LHC18 混合时，它们会形成共凝胶，并根据偶氮苯部分上的取代基自组装成各种形态，从纳米管和松散的纳米管到纳米片。醚键和连接到偶氮苯部分的羧酸基团的数量起着重要作用。在凝胶形成过程中，LHC18 中的局域分子手性可以转移到偶氮苯部分。结合偶氮苯的顺反异构化，产生了光致和手性可逆凝胶。结果表明，具有两个羧酸基团和醚键的偶氮苯基凝胶显示出明显的光学可逆性，但手性可逆性较低，而具有一个羧酸基团和一个醚键的偶氮苯基凝胶则表现出光和手性的双重可逆性。因此，揭示了偶氮苯的分子结构、凝胶中的自组装纳米结构以及光和手性可逆性之间的关系的新见解。
