title: Ni(II) metalations of [40]- and [42]nonaphyrins(1.1.1.1.1.1.1.1.1): the largest doubly twisted Hückel antiaromatic molecule.
abstract: Ni(II) metalation of [42]nonaphyrin gave two Hückel aromatic [42]nonaphyrin Ni(II) complexes that possess different doubly twisted figure-eight conformations. While these complexes are conformers, the activation barriers for conformational interconversion were found to be exceptionally high. However, one-way isomerization from the higher-energy conformer to the lower-energy conformer can be induced upon treatment with trifluoroacetic acid (TFA). This conformational isomerization has been suggested to proceed via a protonation-induced caterpillar-like conformational rotation of the metal-free hexaphyrin-like segment by examining the similar isomerization of an A3 B6 -type [42]nonaphyrin Ni(II) complex. Rh(I) metalation of the lower-energy [42]nonaphyrin Ni(II) complex afforded a [42]nonaphyrin Ni(II) -Rh(I) hybrid complex, which was oxidized with p-chloranil to produce a [40]nonaphyrin Ni(II) -Rh(I) hybrid complex as the largest doubly twisted Hückel antiaromatic molecule to date.
authors.affiliation: Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan), Fax: (+81)75-753-3970.
authors.forename: Takanori
authors.initials: T
authors.lastname: Soya
authors.forename: Koji
authors.initials: K
authors.lastname: Naoda
authors.forename: Atsuhiro
authors.initials: A
authors.lastname: Osuka
keywords: antiaromaticity; aromaticity; conformer; nickel metalation; nonaphyrin