The synthesis of donor–acceptor conjugated polymers using Au- and Ag-catalyzed cross dehydrogenative coupling was achieved for the first time.

This review presents the recent advances in the synthesis of organic semiconductors using C–H functionalization and naturally sourced building blocks to facilitate the large-scale production and commercialization of organic semiconductors.

The Carothers equation is often used to predict the utility of a small molecule reaction in a polymerization. In this study, we present the mechanistic study of Pd/Ag cocatalyzed cross dehydrogenative coupling (CDC) polymerization to synthesize a donor−acceptor (D−A) polymer of 3,3′-dihexyl-2,2′-bithiophene and 2,2′,3,3′,5,5′,6,6′-octafluorobiphenyl, which go counter to the Carothers equation. It is uncovered that the second chain extension cross-coupling proceeds much more efficiently than the first crosscoupling and the homocoupling side reaction (at least 1 order of magnitude faster) leading to unexpectedly low homocoupling defects and high molecular weight polymers. Kinetic analyses show that C−H bond activation is rate-determining in the first crosscoupling but not in the second cross-coupling. Based on DFT calculations, the high cross-coupling rate in the second cross-coupling was ascribed to the strong Pd-thiophene interaction in the Pdmediated C−H bond activation transition state, which decreases the energy barrier of the Pd-mediated C−H bond activation. These results have implications beyond polymerizations and can be used to ease the synthesis of a wide range of molecules where C−H bond activation may be the limiting factor.