Visible Light-Induced Synthesis of Conjugated Poly(phenylene butadiynylene) by a Combination of Halide Abstraction and Coupling Reactions

Abstract

This study describes a simple and efficient method for synthesizing conjugated poly(phenylene butadiynylene) (PPB)polymers using photo-induced radical homocoupling. The approach involves irradiating 1,4-bis(bromoethynyl)benzene with visible light in the presence of dimanganese decacarbonyl (Mn2(CO)10), which acts as a radical generator by abstracting halides and promoting subsequent radical coupling reactions. The resulting conjugated PPB exhibited a remarkable red shift, and the optical band gap decreased from −2.76 to −2.27 eV. A similar effect was observed in the electrochemically measured oxidation potential; the highest occupied molecular orbital position regressed from −6.06 to −5.69 eV. Transmission electron microscopy and atomic force microscopy measurements revealed the self-organization of the polymers to planar 2D nanorods, and the 2D structures of the polymers were further supported by density functional theory calculations. Moreover, the surface area of the polymer was found to be 53.61 and 30.69 m2/g according to Brunauer-Emmett-Teller and Barrett-Joyner-Halenda methods, respectively.