Highly selective palladium-catalyzed Stille coupling reaction toward chlorine-containing NIR electroluminescent polymers

Abstract

High selectivity and yield of aryl–aryl coupling reactions between chlorine-containing aromatic bromides and organotin reagents are reported. The variable reaction selectivity between bromine and chlorine mainly depends on the electronic effects of the aromatic substrates. The reactivity of chlorine can be completely restrained by employing the optimized palladium catalysts, which can be used for the preparation of chlorine-bearing molecules. Then, a series of high molecular weight conjugated copolymers with chlorine on the backbones are straightforwardly synthesized by the Stille condensation reaction. The chlorine-bearing polymers exhibit much lower LUMO, larger Stokes shift and less self-absorption compared with the non-chlorine analogues because of the electron affinity and the large steric hindrance of chlorine atoms. Efficient NIR emission centred at about 758 nm can be obtained based on the single layer system.