Harnessing Radical-Based Dynamic Covalent Chemistry and Supramolecular Synthon for Directional Self-Assembly

The discovery of new weak supramolecular interactions and supramolecular synthons is essential for directing self-assembly processes with enhanced precision, diversity, and functionality in complex molecular architectures. Here, we report the controlled self-assembly of diverse supramolecular architectures by a new directional bonding approach through the integration of radical-based dynamic covalent chemistry and supramolecular synthons. A novel macrocyclic synthon, S1, with a linear direction is constructed via radical-based dynamic covalent bonds from the phenothiazine building block substituted with two dicyanomethyl radicals. By coupling S1 with phenanthrene- and carbazole-based linkers with different angles, we achieve precise and controllable self-assembly. As anticipated, when S1 is paired with a 60° phenanthrene linker, a triangular superstructure, the macrocycle-bridged macrocycle M1, is formed. Notably, coupling S1 with a nearly 90° carbazole linker yields two distinct superstructures, M2 and M3, with triangular and quadrangular geometries, respectively. Interestingly, both the synthon and its assembled superstructures exhibit intriguing thermal association and dissociation behaviors, facilitated by the formation of stable chromogenic radicals. This dynamic process was thoroughly investigated by using VT-UV-vis-NIR, VT-NMR, and VT-EPR spectroscopies. More significantly, the reversible dissociation and association of radical-based dynamic covalent bonds enable the full thermal conversion of M2 and M3. This study highlights the potential of integrating radical-based dynamic covalent chemistry with supramolecular synthons as an emerging strategy for the precise construction of sophisticated and multifunctional supramolecular architectures, paving the way for the development of novel stimuli-responsive materials.