Copper(i) oxide nanoparticle-mediated C–C couplings for synthesis of polyphenylenediethynylenes: evidence for a homogeneous catalytic pathway

Abstract

During the last few decades, substantial attention has been devoted to copper and copper oxide nanocatalysts, due to copper s natural abundance, low cost and lower toxicity in comparison to precious metal-based nanoparticles. Cuprous oxide (Cu2O) nanoparticles show versatility in catalyzing and mediating carbon–carbon (C–C) and carbon–heteroatom (e.g., C–N, C–O, C–S and C–Se) bond-forming reactions. Here, we demonstrate Cu2O nanoparticle-mediated oxidative C–C homocoupling reactions for the synthesis of polyphenylenediethynylenes under ligandless conditions, mild base and atmospheric air as the oxidant, with reasonable yields and moderate number-average molecular weights. Also, we demonstrate that, during the reaction, Cu2O nanoparticles undergo substrate-induced leaching to form homogeneous copper catalytic species. The leaching of catalytic species and in situ formation of copper complexes are characterized by electrospray ionization mass spectrometry, ultraviolet-visible extinction spectroscopy, transmission electron microscopy and reactor study. The results confirm the contribution of a homogeneous catalytic pathway for the oxidative C–C homocoupling reactions under the reaction conditions used.