Banno Motonori, Wu Zong-Quan, Makiguchi Wataru, Furusho Yoshio, Yashima Eiji
Department of Molecular Design and Engineering, Graduate School of Engineering, Nagoya University, Chikusa-ku, Nagoya, 464-8603 (Japan), Fax: (+81) 52-789-3185.
Current address: School of Chemical Engineering, Hefei University of Technology, Hefei Anhui Province 230009 (P. R. China).
Chempluschem. 2014 Jan;79(1):35-44. doi: 10.1002/cplu.201300108. Epub 2013 Sep 24.
Optically active amidine ((R)-1) and achiral carboxylic acid (2) dimers with a m-terphenyl backbone linked by a 1,4-phenylene diacetylene unit form a double helix, (R)-1⋅2, through complementary amidinium-carboxylate salt bridges in THF. Upon the addition of poor solvents, such as n-hexane, the duplex forms an organogel as a result of supramolecular polymerization of the duplex by intermolecular rearrangement of the salt bridges. In sharp contrast, an analogous racemic duplex composed of achiral amidine residues and an optically active duplex linked by a shorter diacetylene unit with a higher binding affinity than that of (R)-1⋅2 does not show any gelation. The supramolecular fluorescent gels exhibit reversible thermo- and chemoresponsive behavior. The chiroptical properties of the gels, the mechanism of gelation, and the amplification of helical chirality during the gelation of (R)-1⋅2 in the absence and presence of its enantiomeric counterpart, (S)-1⋅2, and a racemic duplex, consisting of achiral amidine and carboxylic acid dimers, were investigated by following changes in the absorption and circular dichroism spectra.
具有间三联苯主链且通过1,4 - 亚苯基二乙炔单元连接的光学活性脒（(R)-1）和非手性羧酸（2）二聚体，在四氢呋喃中通过互补的脒鎓 - 羧酸盐桥形成双螺旋结构，即(R)-1⋅2。加入不良溶剂（如正己烷）后，由于盐桥的分子间重排导致双螺旋超分子聚合，该双链体形成有机凝胶。与之形成鲜明对比的是，由非手性脒残基组成的类似外消旋双链体以及由较短二乙炔单元连接且具有比(R)-1⋅2更高结合亲和力的光学活性双链体，均未表现出任何凝胶化现象。这些超分子荧光凝胶呈现出可逆的热响应和化学响应行为。通过跟踪吸收光谱和圆二色光谱的变化，研究了凝胶的手性光学性质、凝胶化机制以及在不存在和存在其对映体(S)-1⋅2以及由非手性脒和羧酸二聚体组成的外消旋双链体的情况下，(R)-1⋅2凝胶化过程中螺旋手性的放大情况。
