Constructing 1-Ethoxyphenanthro[9,10- e ]acephenanthrylene for the Synthesis of a Polyaromatic Hydrocarbon Containing a Formal Azulene Unit.

peri -Acenoacenes are attractive synthetic targets, but their non-benzenoid isomeric counterparts were unnoticed. 1-Ethoxyphenanthro[9,10- e ]acephenanthrylene 8 was synthesized and converted to azulene-embedded 9 , which is a tribenzo-fused non-alternant isomeric motif of peri -anthracenoanthracene. Aromaticity and single-crystal analyses suggested a formal azulene core for 9 , which showed a smaller highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy gap with a charge-transfer absorption band and brighter fluorescence than 8 (quantum yield (Φ): 9 = 41.8%, 8 = 8.9%). The reduction potentials of 8 and 9 were nearly identical, and the observations were further supported by density functional theory (DFT) calculations.