Heptannulated Perylene Diimides: Formation and Reactivity of Electron‐Deficient Tropylium Cations and Heptafulvenes

Abstract

The development of new π‐conjugated motifs opens pathways to previously unexplored classes of organic semiconductors and functional dyes. In this study, five‐ and seven‐membered carbocycles were fused at the ortho and bay regions of electron‐deficient perylenes, starting from a common dialdehyde precursor. Structural analysis of the resulting perylene tetraesters, dianhydrides, and diimides (PDIs) revealed three distinct ring‐fusion patterns and defined stereochemistry. The fused PDI cycloheptatrienes demonstrated susceptibility to acid‐catalyzed transarylation, involving tropylium cation intermediates, which can be used preparatively. Under superacidic conditions, the PDI tropylium cations were directly observed and shown to undergo hydride‐transfer reductions. Additionally, a fused PDI bis(heptafulvene) was synthesized by dehydrogenating a suitably substituted PDI cycloheptatriene. The final system contains two quinomethane units, which can be protonated to yield a stable tropylium‐like dication.