Direct Arylation Polycondensation of Chlorinated Thiophene Derivatives to High-Mobility Conjugated Polymers

High-mobility
conjugated polymers (CPs) that can be synthesized
in a large scale by direct arylation polycondensation (DArP) are highly
desired for printable electronics. To realize this purpose, a readily
accessible C–H monomer with high reactivity and selectivity
is crucial. Herein, we demonstrated that chlorination enables the
efficient DArP of thiophene derivatives, i.e., 3,3′,4,4′-tetrachloro-2,2′-bithiophene
(4ClBT) and (E)-1,2-bis­(3,4-dichlorothien-2-yl)­ethene
(4ClTVT), which can be prepared with no more than two steps. No evidence
of structure defects was found in the resulting polymers. This finding
allows the facile synthesis of high-molecular-weight CPs via DArP.
The presence of Cl···S weak intramolecular interaction,
which can improve the coplanarity of conjugated skeleton, was confirmed
by single-crystal structural analysis. With diketopyrrolopyrrole derivatives
as C–Br monomers, CPs with electron mobility up to 1.44 cm2 V–1 s–1 in air have been
obtained via DArP. This work demonstrates that chlorinated thiophene
derivatives are promising C–H monomers for large-scale synthesis
of high-mobility CPs via an atom-economical and “green”
method, i.e., DArP.