Ambient and metal-free C(sp2)–C(sp3) cross-coupling polymerization of dichalcones and activated methylenes to prepare clusteroluminescent polyarylacrylonitriles
Abstract
Carbon–carbon (C–C) bond cross-coupling is an important tool for constructing functional polymers, yet it typically relies on expensive transition metal catalysts and inert atmospheres. In this study, we designed a class of chalcone derivatives and established their metal-free C(sp2)–C(sp3) cross-coupling polymerization and activated methylenes via C(sp3)–H Michael addition under ambient conditions. 16 polyarylacrylonitriles (PAANs) with diverse structures and high molecular weights (Mw up to 60 200) were obtained in high yields (up to 96.6%). Remarkably, PAANs without conventional luminophores exhibited enhanced fluorescence compared to their monomeric counterparts, demonstrating distinct polymerization-induced emission (PIE) and clusterization-triggered emission (CTE) phenomena. The study of photophysical properties and theoretical calculations prove that the emission mechanism of PAANs is attributed to the through-space conjugation (TSC) between heteroatoms (N and O) and separated benzene rings in the polymer structure. In addition, the fluorescent PAANs selectively detect Fe3+ with a low detection limit of 4.55 × 10−5 M.