Ambient and Metal-Free C(sp2 )-C(sp3 ) Cross-Coupling Polymerization of Dichalcones and Activated Methylenes to Prepare Clusteroluminescent Polyarylacrylonitriles

Abstract

The carbon-carbon (C–C) bonds cross-coupling is an important tool in constructing functional polymers, yet it typically relies on expensive transition metal catalysts and inert atmospheres. In this study, we designed a kind of chalcone derivatives, and established a metal-free C(sp2)–C(sp3) cross-coupling polymerization of them 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 luminephore 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) of 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.