Nickel norcorrole provides an unusual example of a molecule that is strongly antiaromatic according to the magnetic criterion, but which exhibits, according to high-quality DFT calculations, a symmetric, delocalized structure with no difference in bond length between adjacent Cmeso-Cα bonds. A fragment molecular orbital analysis suggests that these discordant observations are a manifestation of the high stability of the dipyrrin fragments, which retain their electronic and structural integrity even as part of the norcorrole ring system.

CEITEC Central European Institute of Technology Masaryk University Kamenice 5 CZ 62500 Brno Czech Republic

Department of Chemistry UiT The Arctic University of Norway 9037 Tromsø Norway

Department of Chemistry University of the Free State 9300 Bloemfontein Republic of South Africa

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