Seeding Control in\nChirality Triggering of Red-Emitting\nOrganic Charge-Transfer Cocrystal Helixes from Achiral Molecules

Supramolecular chirality has gained immense attention\nfor great\npotential, in which the rational engineering strategy facilitates\nunique helical stacking/assembly, high chiroptical behavior, and prime\nbiomedical activity. In this study, we reported a novel chiral organic\ndonor–acceptor cocrystal based on asymmetrical components of\nbenzo(<i>b</i>)naphtho(1,2-<i>d</i>)thiophene\n(BNT) and 9-oxo-9H-indeno(1,2-<i>b</i>)pyrazine-2,3-dicarbonitrile\n(DCAF) that exhibited red emission using a simple solution approach.\nDuring the self-assembly, a kinetically controlled growth of polar\nsolvent or substrate induction led to the chiral packing and helical\nmorphology twisted by the cooperation of electrostatic potential energy\nand chirality. Intriguingly, a “seeding-control” mechanism\nwas newly developed for the production of <i>c</i>-BNT–DCAF\nhelical crystals with a defined uniform chiral form, which enables\nchirality transfer and amplification from the microscopic to macroscopic\nlevel via supramolecular stacking. By introducing chiral additives\nor even a small break at the edge, the first nucleus acted as a chiral\nseeding to guide the donor/acceptor molecule alignment into the same\nhandedness. A remarkably high dissymmetry factor (<i>g</i><sub>lum</sub>) value of 0.1 was demonstrated on the chiral manipulated\nribbons, which is the highest among the reported charge-transfer complexes.\nThis work offers us more paths for the design of chiral supramolecular\nsystems for vital applications in organic optoelectronics, micro/nanomechanics,\nand biomimetics.