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 (M_w 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.