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

This study describes a simple and efficient method forsynthesizingconjugated poly(phenylene butadiynylene) (PPB)polymers using photo-inducedradical homocoupling. The approach involves irradiating 1,4-bis(bromoethynyl)benzenewith visible light in the presence of dimanganese decacarbonyl (Mn-2(CO)(10)), which acts as a radical generator by abstractinghalides and promoting subsequent radical coupling reactions. The resultingconjugated PPB exhibited a remarkable red shift, andthe optical band gap decreased from -2.76 to -2.27 eV.A similar effect was observed in the electrochemically measured oxidationpotential; the highest occupied molecular orbital position regressedfrom -6.06 to -5.69 eV. Transmission electron microscopyand atomic force microscopy measurements revealed the self-organizationof the polymers to planar 2D nanorods, and the 2D structures of thepolymers were further supported by density functional theory calculations.Moreover, the surface area of the polymer was found to be 53.61 and30.69 m(2)/g according to Brunauer-Emmett-Tellerand Barrett-Joyner-Halenda methods, respectively.