Norcorrole is a ring-contracted porphyrin bearing 16π-electronic conjugation, of which synthesis has been quite challenging.  Recently, we have succeeded to synthesize norcorrole Ni(II) complex 1 in over 90% yield from a dibromodipyrrin precursor via metal-templated strategy.  We elucidated the planar structure and distinct antiaromatic nature of 1. Contrary to our expectation, meso-dimesitylnorcorrole Ni(II) 1 was quite stable under air at room temperature.  The reactivity of 1 was also investigated. Although stable at room temperature, 1 was oxidized to 18π-aromatic oxacorrole under oxygen at 100 °C.  In addition, the facile reduction and oxidation reaction of 1was applied to fabricate rechargeable batteries, which exhibited excellent charge/discharge capacity and durability.

We have also prepared N,N’-dihydrodiazaporphyrins 2 through chemo- and regioselective reduction of diazaporphyrins.  The structure and properties of this novel porphyrinoids have been investigated. N,N’-dihydrodiazaporphyrins 2 was found to be antiaromatic because of their 20π-conjugation including lone pairs on nitrogen atoms and their highly planar structures.