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

Abstract

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.

Conflicting evidence for ferroelectricity

“…We also find, as in Ref. 3, that a better structural refinement is obtained for the non-polar space group P-1, than for the P1 group initially proposed. Density functional theory (DFT) calculations consistently indicate that the non-polar phases are the most stable for the three LASO compounds.…”

“…We note that the X-ray diffraction data of the three LASO crystals has been recently re-examined by the same authors, assigning all of them to centro-symmetric space groups 3 , clearly incompatible with ferroelectricity.…”

“…Tayi et al 1 reported room temperature ferroelectricity in organic mixed-stack charge transfer (CT) crystals, resulting from a novel supramolecular design concept, the Lock-Arm Supramolecular Ordering (LASO) that synergistically combines intermolecular CT and hydrogen bonds 2,3 . Here we present an independent experimental investigation that found no evidence for ferroelectricity in one of the LASO crystals and, together with theoretical calculations, demonstrates that a possible ferroelectric behaviour is not of electronic origin as originally proposed.…”

Thermally Reduced Graphene Oxide Nanohybrids of Chiral Functional Naphthalenediimides for Prostate Cancer Cells Bioimaging

“…A crystalline red powder was obtained by recrystallizing D-3• coronene from N -methylpyrrolidone and H 2 O. [ 64 ] The TEM micrographs of D -3• coronene shown in Figure 11 e indicates the formation of crystalline organic nanoparticles of the relevant complex together with amorphous material (Figure 11 , and D-6 can be easily monitored using fl uorescence spectroscopy in solution. They are consistent with the expectations for systems that act as sensor candidates because of the tunability of fl uorescent properties.…”

Organic cocrystals: the development of ferroelectric properties

“…4), a molecular design that allows donor and acceptor molecules to self-assemble into charge-transfer ferroelectric networks at ambient temperature [18][19]. New structures arising from this technique challenge the long-standing notion that donor-acceptor mixed-stack materials cannot exhibit a ferroelectric T c greater than room temperature.…”