Highly Twisted 1,2:8,9‐Dibenzozethrenes: Synthesis, Ground State, and Physical Properties

Two soluble and stable 1,2:8,9‐dibenzozethrene derivatives ( 3 a,b ) are synthesized through a palladium‐catalyzed cyclodimerization reaction. X‐ray crystallographic analysis shows that these molecules are highly twisted owing to congestion at the cove region. Broken‐symmetry DFT calculations predict that they have a singlet biradical ground state with a smaller biradical character and a large singlet–triplet energy gap; these predictions are supported by NMR and electronic absorption measurements. They have small energy gaps and exhibit far‐red/near‐infrared absorption/emission and amphoteric redox behaviors.