Chiral Coassembly and Supramolecular Substitution in a Mutual-Binding Ternary Nanosystem: Implications for Surface Luminescent Modification

Chiral coassembly that noncovalently incorporates distinct species is an efficient approach to constructing functional chiroptical materials with dynamically controlled properties. However, rational and precise manipulation of the coassembly pathway in multiple-component chiral systems containing three or more species remains a great challenge, and the understanding toward the coassembly selectivity is insufficient. To address these issues, in this work, we introduced a coassembly system containing three species that could mutually bind to each other. Model compounds comprising a chiral π-conjugated amino acid (F5), an electron-rich bipyridine derivative (BPE), and an electron-deficient acceptor (TCNB) were chosen. Interplays between F5/TCNB, F5/BPE, and BPE/TCNB indicated complex pathways in ternary mixing. F5/BPE/TCNB mixing selectively prefers F5/BPE combination that excludes TCNB due to protonation of bipyridines from amino acids that hinders the charge transfer and hydrogen bonds between BPE and TCNB. This selectivity allows for an in situ supramolecular substitution process that adding BPE into F5/TCNB complexes could substitute TCNB to generate F5/BPE coassemblies without breaking the gel morphology, which is assigned as [F5/TCNB]* + BPE → [F5/BPE]* + TCNB. This process unveils the selectivity in three-component chiral self-assembly systems that is useful in fabricating advanced responsive chiroptical materials and realizing the modification of luminescence in a top-down protocol.