Synthesis of a 1,2-Dithienylethene-Containing Donor-Acceptor Polymer via Palladium-Catalyzed Direct Arylation Polymerization (DArP)

This paper reports the synthesis of D-A polymers containing 1,2-dithienylethene (DTE) units via palladium-catalyzed direct arylation polymerization (DArP). The reaction of dibromoisoindigo (1-Br) and DTE (2-H), in the presence of Pd-2(dba)(3)center dot CHCl3 (0.5 mol%), P(2-MeOC6H4)(3) (L1) (2 mol%), pivalic acid (1 equiv) as catalyst precursors, and Cs2CO3 (3 equiv) as a base affords poly(1-alt-2) with a high molecular weight (Mn up to 44,900). Although, it has been known that monomers, with plural C-H bonds, tend to form insoluble materials via direct arylation at undesirable C-H positions; the reaction of 1-Br and 2-H cleanly proceeds without insolubilization. The resulting polymer has a well-controlled structure and exhibits good charge transfer characteristics in an organic field-effect transistor (OFET), compared to the polymer produced by Migita-Kosugi-Stille cross-coupling polymerization. The DArP product displays an ideal linear relationship in the current-voltage curve, whereas the Migita-Kosugi-Stille product shows a V-G-dependent change in the charge mobility.