Lock-Arm Supramolecular Ordering: A Molecular Construction Set for Cocrystallizing Organic Charge Transfer Complexes

Organic
charge transfer cocrystals are inexpensive, modular, and solution-processable
materials that are able, in some instances, to exhibit properties
such as optical nonlinearity, (semi)­conductivity, ferroelectricity,
and magnetism. Although the properties of these cocrystals have been
investigated for decades, the principal challenge that researchers
face currently is to devise an efficient approach which allows for
the growth of high-quality crystalline materials, in anticipation
of a host of different technological applications. The research reported
here introduces an innovative design, termed LASOlock-arm
supramolecular orderingin the form of a modular approach for
the development of responsive organic cocrystals. The strategy relies
on the use of aromatic electronic donor and acceptor building blocks,
carrying complementary rigid and flexible arms, capable of forming
hydrogen bonds to amplify the cocrystallization processes. The cooperativity
of charge transfer and hydrogen-bonding interactions between the building
blocks leads to binary cocrystals that have alternating donors and
acceptors extending in one and two dimensions sustained by an intricate
network of hydrogen bonds. A variety of air-stable, mechanically robust,
centimeter-long, organic charge transfer cocrystals have been grown
by liquid–liquid diffusion under ambient conditions inside
72 h. These cocrystals are of considerable interest because of their
remarkable size and stability and the promise they hold when it comes
to fabricating the next generation of innovative electronic and photonic
devices.

有机电荷转移共晶体（organic charge transfer cocrystals）是一类低成本、模块化且可溶液加工的材料，在部分场景中可展现出光学非线性、（半）导电性、铁电性及磁学特性。尽管这类共晶体的特性已被研究数十年，但当前研究者面临的核心挑战仍是开发高效方法以制备高质量晶体材料，从而满足各类技术应用的需求。本研究提出了一种创新设计策略——命名为LASO（锁臂超分子有序，lock-arm supramolecular ordering），以模块化路径开发响应型有机共晶体。该策略依托芳香族电子给体与受体构筑基元，这类基元带有互补的刚性与柔性臂段，可形成氢键以强化共结晶过程。构筑基元间电荷转移与氢键相互作用的协同效应，可得到二元共晶体，其中给体与受体交替排列，在一维与二维方向延伸，并由复杂的氢键网络维系结构稳定。本研究通过常温下的液液扩散法，在72小时内制备出多种空气稳定、机械性能优异且长度可达厘米级的有机电荷转移共晶体。这类共晶体凭借其优异的尺寸特性、稳定性，以及在制备下一代创新型电子与光子器件方面的应用潜力，受到了广泛关注。