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 Pd₂(dba)₃·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 ( M n 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.