Phenylene-Bridged Expanded Porphyrazines.

Novel expanded porphyrazines comprising o- and p-phenylene units were synthesized from self-condensation reactions of acyclic [2+1]-type precursors prepared from 1,3-diiminoisoindoline and the corresponding phenylenediamines. Möbius and Hückel topological structures of [4+2]-type and [3+2]-type expanded porphyrazines, respectively, were elucidated by X-ray crystallography. Despite the Möbius and Hückel [4n]π-electron systems, these expanded porphyrazines are virtually nonaromatic as a result of their flexible structures in solution, which may diminish intrinsic aromaticity and antiaromaticity.