Department of Chemistry, Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pune 411008, Maharashtra, India.
Chemistry. 2012 Sep 17;18(38):11987-93. doi: 10.1002/chem.201200705. Epub 2012 Aug 9.
Self-organization of organic molecules through weak noncovalent forces such as CH/π interactions and creation of large hierarchical supramolecular structures in the solid state are at the very early stage of research. The present study reports direct evidence for CH/π interaction driven hierarchical self-assembly in π-conjugated molecules based on custom-designed oligophenylenevinylenes (OPVs) whose structures differ only in the number of carbon atoms in the tails. Single-crystal X-ray structures were resolved for these OPV synthons and the existence of long-range multiple-arm CH/π interactions was revealed in the crystal lattices. Alignment of these π-conjugated OPVs in the solid state was found to be crucial in producing either right-handed herringbone packing in the crystal or left-handed helices in the liquid-crystalline mesophase. Pitch- and roll-angle displacements of OPV chromophores were determined to trace the effect of the molecular inclination on the ordering of hierarchical structures. Furthermore, circular dichroism studies on the OPVs were carried out in the aligned helical structures to prove the existence of molecular self-assembly. Thus, the present strategy opens up new approaches in supramolecular chemistry based on weak CH/π hydrogen bonding, more specifically in π-conjugated materials.
有机分子通过弱非共价相互作用（如 CH/π 相互作用）的自组织以及在固态中形成大的分级超分子结构正处于研究的早期阶段。本研究报告了基于定制设计的寡聚苯乙烯基乙烯（OPV）的 CH/π 相互作用驱动的分级自组装的直接证据，这些 OPV 的结构仅在尾部的碳原子数上有所不同。这些 OPV 合成子的单晶 X 射线结构已被解析，并且在晶格中揭示了长程多臂 CH/π 相互作用的存在。发现这些π共轭 OPV 在固态中的排列对于在晶体中产生右手鱼骨堆积或在液晶中间相产生左手螺旋至关重要。OPV 发色团的螺距和滚转角位移被确定为追踪分子倾斜对分级结构有序性的影响。此外，在取向螺旋结构中对 OPV 进行了圆二色性研究，以证明分子自组装的存在。因此，本研究策略为基于弱 CH/π 氢键的超分子化学，特别是在π共轭材料中，开辟了新的途径。
