Helical mesoscopic crystals based on an achiral charge-transfer complex with controllable untwisting/breaking.

The development of synthetic helical structures from achiral molecules and stimulus-responsive shape transformations are vital for biomimetics and mechanical actuators. A stimulus regarded as the force to induce chirality modulation plays a significant role in the helical supramolecular structure design through symmetry breaking. Herein, we synthesized a metastable complex Form 1 crystal composed of pyrene and (4,8-bis(dicyanomethylene)-4,8-dihydrobenzo[1,2-b:4,5-b']-dithiophen-e) DTTCNQ components with a torsional backbone by C-H⋯N hydrogen bonds via a quick cooling method. The helix motion kinetics of Form 1 depends on the intrinsic factor (crystal thickness) and external stimuli (polar solvents). The self-assembled helical microstructures grow into needle-like crystals in liquid media via an untwistingprocess. Furthermore, they undergo predictable deformation of untwisting or breaking under a stimulus-responsive strain-relaxing phase transformation. This work illustrates a new approach in the mediated formation of helical morphologies from achiral binary supramolecules and dynamic motion, which is vital for biomimetics and mechanical actuators.

Functional Carbazole-Fullerene Complexes: A New Perspective of Carbazoles Acting as Nano-Octopus to Capture Globular Fullerenes.

Fullerene host-guest constructs have attracted increasing attention owing to their molecular-level hybrid arrangements. However, the usage of simple carbazolic derivatives to bind with fullerenes is rare. In this research, three novel carbazolic derivatives, containing a tunable bridging linker and carbazole units for the capturing of fullerenes, are rationally designed. Unlike the general concave-convex interactions, fullerenes could interact with the planar carbazole subunits to form 2-dimensional hexagonal/quadrilateral cocrystals with alternating stacking patterns of 1 : 1 or 1 : 2 stoichiometry, as well as the controllable fullerene packing modes. At the meanwhile, good electron-transporting performances and significant photovoltaic effects were realized when a continuous C60⋅⋅⋅ C60 interaction channel existed. The results indicate that the introduction of such carbazolic system into fullerene receptor would provide new insights into novel fullerene host-guest architectures for versatile applications.

Molecule Recognition and Release Behavior of Naphthalenediimide Derivative via Supramolecular Interactions.

Self-assembled charge-transfer complexes based on supramolecular interactions have attracted immense research interest due to their unique packing and (opto)electronic applications. Herein, two new binary cocrystals with a similar 1:1 mixed-stack arrangement are synthesized by solvent evaporation or grinding method using N,N'-dimethyl-1,4,5,8-naphthalene tetracarboxylic diimide (Me-NDI) as the receptor. Single-crystal X-ray diffraction analysis confirms the successful molecular-level recognition and various weak interaction networks. Upon thermal treatment of 1,4,8,11-tetramethyl-6,13-triethylsilylethynyl pentacene (TMTES-P)/Me-NDI complex, in situ cocrystal-to-crystal conversion is observed, and the receptor is gradually released, while the perylene/Me-NDI cocrystal disassembles in the same manner as a single-component compound. The aligned short-contact network, good stability of TMTES-P, and anisotropic attachment energies of the TMTES-P/Me-NDI cocrystal disassemble in a manner same to that of a single-component compound. The aligned short-contact network, good stability of TMTES-P, and anisotropic attachment complexes are believed to promote the release of specific molecules. These structure-property relationship results provide new insights into the design of a supramolecular class with desired functionalities in terms of self-assembled recognition, release, or crystal conversion.

Multifunctional Features of Organic Charge-Transfer Complexes: Advances and Perspectives.

The recent progress of charge-transfer complexes (CTCs) for application in many fields, such as charge transport, light emission, nonlinear optics, photoelectric conversion, and external stimuli response, makes them promising candidates for practical utility in pharmaceuticals, electronics, photonics, luminescence, sensors, molecular electronics and so on. Multicomponent CTCs have been gradually designed and prepared as novel organic active semiconductors with ideal performance and stability compared to single components. In this review, we mainly focus on the recently reported development of various charge-transfer complexes and their performance in field-effect transistors, light-emitting devices, lasers, sensors, and stimuli-responsive behaviors.