Highly Efficient Benzannulation of Poly(phenylene ethynylene)s

摘要

Macromolecules linked by single bonds between aromatic substituents, that is, polyphenylenes, have attracted great interest for use in organic light-emitting diodes (OLEDs) and other optoelectronic devices, as structurally rigid dendrimers, for isolating or organizing chromophores, and as soluble precursors of nanostructured forms of gra-phene. Para- and meta-linked polyphenylenes with high molecular weight are synthesized through transition-metal-catalyzed cross-coupling approaches, some of which proceed through chain-growth mechanisms. Only a few oligomeric ortho-linked phenylenes have been reported as a result of poor cross-coupling efficiency during the polymerization. Longer o-polyphenylenes are interesting because they can adopt specific helical conformations induced by steric interactions along the polymer backbone and can be oxidized to soluble, structurally precise graphene nanoribbons. New strategies for accessing o-polyphenylenes, particularly those that tolerate additional aromatic substituents, are therefore of great utility.