Kinetic Programming of Heteromolecular Contacts in Boron- and Nitrogen-Containing π-Systems via External and Internal Cross-Seeding

We establish a kinetic strategy for controlling the supramolecular copolymerization of boron- and nitrogen-containing π-electron systems by exploiting intramolecular hydrogen bonding in cystine-based dimeric diamides. Two dimeric diamides bearing solubilizing alkyl chains, DBB and DNN, were designed and synthesized by functionalization with planarized triarylborane (PTAB) and planarized triarylamine (PTAA) units, respectively. In low-polarity solvents, both molecules form one-dimensional nanostructures upon ultrasonication. Intramolecular hydrogen bonding between the two diamide units within the cystine framework suppresses spontaneous nucleation and generates metastable monomeric states, thereby providing a kinetic window for seeded supramolecular polymerization. Despite a difference of more than 10 kJ mol–1 between their Gibbs free energy changes for homopolymerization, external cross-seeding with preformed DBB seeds initiates the supramolecular polymerization of metastable DNN monomers. The resulting supramolecular copolymers exhibit long-lived emission arising from spatially confined interactions between the PTAB and PTAA units. The extent of heteromolecular contact formation can be modulated by switching between external and internal cross-seeding protocols. In the internal cross-seeding process, DBB assemblies are generated in situ in the presence of DNN monomers, enabling their incorporation during supramolecular growth and producing coassemblies with an enhanced contribution of heteromolecular excited-state interactions. These results demonstrate that kinetic control over nucleation and elongation enables pathway-dependent regulation of heteromolecular contacts in equimolar binary supramolecular polymers with markedly different homopolymerization propensities.