Dual Trapping of a Metastable Planarized Triarylborane π‑System Based on Folding and Lewis Acid–Base Complexation for Seeded Polymerization

• Published in: Journal of the American Chemical Society Vol. 143; no. 7; pp. 2953 - 2961
• Main Authors: Choi, Heekyoung, Ogi, Soichiro, Ando, Naoki, Yamaguchi, Shigehiro
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 24.02.2021; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Multidisciplinary; Physical Sciences; Science & Technology
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.0c13353

We report the kinetically controlled supramolecular polymerization of boron-containing π-conjugated molecules, which was enabled by a seeding method based on dual trapping of a metastable state by synergistic intramolecular hydrogen bonding and Lewis acid-based complexation. Planarized triarylborane-based 1, which bears a diamide chain with chiral alkyl groups, was synthesized. Upon cooling, the solution of monomer 1 afforded a supramolecular polymerization in a cooperative manner to form helical supramolecular nanostructures with intense J-type aggregate emission. In the presence of pyridine, the triarylborane moiety formed a Lewis acid–base complex, which enhances the stabilization of the metastable monomeric state. An assembly incompetent structure with a folded diamide chain conformation and a pyridine moiety axially coordinated to the boron atom is responsible for slowing the spontaneous aggregation. The seeding method was successfully applied to the solution to produce homogeneous nanofibers even at a high (millimolar-level) concentration. This unprecedented kinetic control via dual trapping provides an effective method to achieve seed-initiated polymerization under concentrated conditions.