Supramolecular Chirality Issues in Unorthodox Naphthalene Diimide Gelators
Supramolecular Chirality Issues in Unorthodox Naphthalene Diimide Gelators
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DOI：
10.1002/chem.201704825
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发表时间：
2018-02-06
影响因子：
4.3
通讯作者：
Ghosh, Suhrit
中科院分区：
文献类型：
--
作者：
Ghosh, Goutam;Paul, Mithun;Ghosh, Suhrit
本文报道了几种1，3-二羟基官能化萘二酰亚胺（NDI）衍生物的自组装，特别强调了手性对凝胶化的影响以及自组装对电荷载流子迁移率的影响。不含任何长烷基链的非常规胶凝剂（R）-NDI在四氯乙烯（TCE）中表现出自发胶凝。基于X-射线晶体学和粉末X-射线衍射研究，它被确定为梯形氢键链之间的1，3-二羟基基团的形成导致优先螺旋的纤维状结构。同样，（S）-异构体也表现出相同的凝胶化和介观结构，但产生具有相反手性的原纤维。有趣的是，（R）-和（S）-异构体的等摩尔混合物没有显示出任何胶凝能力，而是观察到宏观沉淀，并且与单独的异构体形成鲜明对比，混合物的形态显示出不明确的近球形聚集体。差示扫描量热法（DSC）研究揭示了由对映体纯胶凝剂（（R）-或（S）-异构体）产生的超分子聚合物的相同结晶峰，这在它们的等摩尔混合物中不存在。然而，具有对映体过量的两种异构体的混合物恢复了胶凝能力和优先螺旋度，这表明手性放大在本系统中通过所谓的“多数规则”效应是有效的。手性诱导也实现了由“军士和士兵”的原则，在超分子组装的非手性NDI胶凝剂的存在下的（R）-或（S）-异构体作为手性掺杂剂。然而，由手性胶凝因子诱导的强螺旋偏置被发现是相反的性质相比，在文献中很少报道的纯手性胶凝因子的自组装。闪光光解时间分辨微波电导率（FP-TRMC）测量表明，凝胶化对电导率的强烈的积极影响。
Herein, the self-assembly of a few 1,3-dihydroxyl functionalized naphthalene diimide (NDI) derivatives has been reported with particular emphasis on the impact of chirality on gelation and the effect of self-assembly on charge-carrier mobility. A nonconventional gelator (R)-NDI, devoid of any long alkyl chains, exhibited spontaneous gelation in tetra-chloroethylene (TCE). Based on X-ray crystallography and powder X-ray diffraction studies, it was established that a ladder-like hydrogen-bonded chain formation between the 1,3-dihydroxyl group leads to the fibrillar structures with preferential helicity. Likewise the (S)-isomer also exhibited identical gelation and mesoscopic structure but produced fibrils with the opposite handedness. Intriguingly, an equimolar mixture of the (R)- and (S)-isomers did not show any gelation ability, rather a macroscopic precipitation was observed and, in sharp contrast to the individual isomers, the morphology of the mixture showed ill-defined near spherical agglomerates. Differential scanning calorimetry (DSC) studies revealed an identical crystallization peak for the supramolecular polymer produced from the enantiopure gelators ((R)- or (S)-isomer), which was absent in their equimolar mixture. However, mixtures of the two isomers with enantiomeric excess retrieved the gelation ability and preferential helicity demonstrating that chiral amplification is operative in the present system through the so-called "majority rule" effect. Chirality induction was also realized by the "sergeant and soldier" principle in the supramolecular assembly of an achiral NDI gelator in the presence of either the (R)- or (S)-isomer as the chiral dopant. However, the strong helical bias induced by the chiral gelator was found to be opposite in nature compared to that found in the self-assembly of the pure chiral gelator that has been rarely reported in the literature. Flash-photolysis time-resolved microwave conductivity (FP-TRMC) measurements indicated the strong positive impact of the gelation on the electrical conductivity.