Stimuli-Responsive Trimorphs and Charge-Transfer Complexes of a Twisted Molecular Donor

Supramolecular self-assemblies and co-assemblies possess multiple noncovalent interactions, highly ordered structures, and multifunctional properties. Yet, the fundamental understanding of their “structure–property relationship” remains very challenging. Herein, two kinetically controlled supramolecular charge transfer (CT) complexes were conceptualized from a trimorphic molecular donor denoted as “twisted aromatic hydrocarbon” (TAH), with p-fluoranil (TFQ) and p-chloranil (TCQ) in water, organic solvent, and solvent-free methods. Elucidating their co-assembling mechanism revealed that segmentation of the TAH with molecules having planar deficient cores spontaneously formed a distinct “H-type mixed stack” and “J-type segregated stack”, regulated by blue/red-shifted charge-transfer and π-π stacking including weak C-H···F and C-H···O noncovalent interactions. By utilizing the structural transformational ability of the self-assembled TAH, the mechanistic aspects for the rapid nanoscopic co-assembly formation were precisely demonstrated experimentally and theoretically. The trimorphs and co-crystals of TAH could be disassembled resulting in turn-on emission by applying various external stimuli and being repeatedly reconfigured, thus providing a unique structure–property relationship and new TAH-based materials. This unique concept offers color-specific polymorphism and CT-complex formation strategy involving a simple class of functional materials having cooperative network forming ability using the twisted molecular donor.