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Twisty phenyl-laden tetracene synthesized

Molecule could have applications in electrochemiluminescence and organic electronics

by Celia Arnaud
January 21, 2019 | A version of this story appeared in Volume 97, Issue 3


Structure of dodecaphenyltetracene showing the end-to-end twist in the molecule.

Researchers have synthesized the longest, most twisted perphenylacene yet. This family of molecules, which includes many important semiconductors, consists of linear fused benzene rings surrounded by pendant phenyl rings. Previously, the largest such molecule had been decaphenylanthracene. Robert A. Pascal Jr. and coworkers at Tulane University have now added another fused benzene ring and two more phenyls, synthesizing dodecaphenyltetracene in three steps (Angew. Chem., Int. Ed. 2019, DOI: 10.1002/anie.201812418). They started by treating a mixture of tetraphenylfuran and 1,2,4,5-tetrabromo-3,6-diphenylbenzene with n-butyllithium to yield a dibromoepoxynaphthalene. They then reacted that molecule with hexaphenylisobenzofuran and n-butyllithium to form a diepoxytetracene. Finally, they removed the oxygen atoms by using a mixture of TiCl3-AlCl3 and n-butyllithium. The resulting dodecaphenyltetracene is deep red and strongly luminescent. The tetracene core has an end-to-end twist of 97°. Although the surrounding phenyls stabilize the molecule, it does undergo slow oxidative decomposition. The work “pushes the concept of twisted conjugation toward longer polyacenes that have potential applications in organic electronics and photovoltaics,” says Christopher Bardeen, a materials chemist at the University of California, Riverside, who was not involved in the study. “This work provides a new strategy for manipulating the shape and electronic properties of the polyacenes.”


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