Otsuka Chie, Takahashi Sho, Isobe Atsushi, Saito Takuho, Aizawa Takumi, Tsuchida Ryoma, Yamashita Shuhei, Harano Koji, Hanayama Hiroki, Shimizu Nobutaka, Takagi Hideaki, Haruki Rie, Liu Luzhi, Hollamby Martin J, Ohkubo Takahiro, Yagai Shiki
Division of Advanced Science and Engineering, Graduate School of Science and Engineering, Chiba University, Chiba 263-8522, Japan.
Center for Basic Research on Materials, National Institute for Materials Science, Tsukuba 305-0044, Japan.
J Am Chem Soc. 2023 Oct 18;145(41):22563-22576. doi: 10.1021/jacs.3c07556. Epub 2023 Oct 5.
Polymorphism, a phenomenon whereby disparate self-assembled products can be formed from identical molecules, has incited interest in the field of supramolecular polymers. Conventionally, the monomers that constitute supramolecular polymers are engineered to facilitate one-dimensional aggregation and, consequently, their polymorphism surfaces primarily when the states of assembly differ significantly. This engenders polymorphs of divergent dimensionalities such as one- and two-dimensional aggregates. Notwithstanding, realizing supramolecular polymer polymorphism, wherein polymorphs maintain one-dimensional aggregation, persists as a daunting challenge. In this work, we expound upon the manifestation of two formed from a large discotic supramolecular monomer (rosette), which consists of six hydrogen-bonded molecules with an extended π-conjugated core. These polymorphs are generated in mixtures of chloroform and methylcyclohexane, attributable to distinctly different disc stacking arrangements. The face-to-face (minimal displacement) and offset (large displacement) stacking arrangements can be predicated on their distinctive photophysical properties. The face-to-face stacking results in a twisted helix structure. Conversely, the offset stacking induces inherent curvature in the supramolecular fiber, thereby culminating in a hollow helical coil (helicoid). While both polymorphs exhibit bistability in nonpolar solvent compositions, the face-to-face stacking attains stability purely in a kinetic sense within a polar solvent composition and undergoes conversion into offset stacking through a dislocation of stacked rosettes. This occurs without the dissociation and nucleation of monomers, leading to unprecedented helicoidal folding of supramolecular polymers. Our findings augment our understanding of supramolecular polymer polymorphism, but they also highlight a distinctive method for achieving helicoidal folding in supramolecular polymers.
多态性是一种由相同分子形成不同自组装产物的现象，它引发了超分子聚合物领域的研究兴趣。传统上，构成超分子聚合物的单体经过设计以促进一维聚集，因此，当组装状态有显著差异时，它们的多态性才会主要表现出来。这就产生了不同维度的多晶型物，如一维和二维聚集体。尽管如此，实现超分子聚合物多态性，即多晶型物保持一维聚集，仍然是一个艰巨的挑战。在这项工作中，我们阐述了由一种大型盘状超分子单体（玫瑰花结）形成的两种多晶型物的表现，该单体由六个具有扩展π共轭核心的氢键分子组成。这些多晶型物是在氯仿和甲基环己烷的混合物中产生的，这归因于明显不同的盘状堆积排列。面对面（最小位移）和错位（大位移）堆积排列可以根据它们独特的光物理性质来预测。面对面堆积导致扭曲的螺旋结构。相反，错位堆积在超分子纤维中诱导固有曲率，从而形成空心螺旋线圈（螺旋体）。虽然两种多晶型物在非极性溶剂组成中都表现出双稳态，但面对面堆积在极性溶剂组成中仅在动力学意义上达到稳定，并通过堆积的玫瑰花结的位错转化为错位堆积。这一过程在单体不解离和成核的情况下发生，导致超分子聚合物出现前所未有的螺旋折叠。我们的发现增进了我们对超分子聚合物多态性的理解，但它们也突出了一种在超分子聚合物中实现螺旋折叠的独特方法。
