Neo-Fused Hexaphyrin: A Molecular Puzzle Containing an N-Linked Pentaphyrin

The first neo-confused hexaphyrin(1.1.1.1.1.0) was synthesized by oxidative ring closure of a hexapyrrane bearing two terminal confused pyrroles. The new compound displays a folded conformation with a short interpyrrolic C center dot center dot center dot N distance of 3.102 angstrom, and thus it readily underwent ring fusion to afford a neo-fused hexaphyrin with an unprecedented 5,5,5,7-tetracyclic ring structure. Furthermore, coordination of Cu-II triggered a ring opening/contracting reaction to afford a Cu-II complex of an N-linked pentaphyrin derivative. The roles of reactive N-C bonds in the porphyrinoid macrocycles were demonstrated.