title: One-handed single helicates of dinickel(II) benzenehexapyrrole-α,ω-diimine with an amine chiral source.
abstract: Benzenehexapyrrole-α,ω-dialdehyde, composed of a pair of formyltripyrrole units with a 1,3-phenylene linker, was metallated to give dinuclear single-stranded helicates. X-ray studies of the bis-nickel(II) complex showed a helical C2 form with a pair of helical-metal coordination planes of a 3N+O donor set. The terminal aldehyde was readily converted into the imine by optically active amines, whereby helix-sense bias was induced. Bis-nickel(II) and bis-palladium(II) complexes of the benzenehexapyrrole-α,ω-diimines were studied to show that an enantiomer pair of the helical C2 form are interchanged by slow flipping of each coordination plane and fast rotation around the C(benzene)C(pyrrole) bond. The helical screw in the bis-nickel(II) complexes was biased to one side in more than 95 % diastereoselectivity, which was achieved by using a variety of optically active amines, such as (R)-1-cyclohexylethylamine, (S)-1- phenylethylamine, L-Phe(OEt) (Phe=phenylalanine), and (R)-valinol. The nickel complexes showed much better diastereoselectivity than the corresponding palladium complexes.
authors.affiliation: Department of Chemistry, Graduate School of Science, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe 657-8501 (Japan), Fax: (+81) 78-803-5770.
authors.forename: Chaolu
authors.initials: C
authors.lastname: Eerdun
authors.forename: Satoshi
authors.initials: S
authors.lastname: Hisanaga
authors.forename: Jun-ichiro
authors.initials: J
authors.lastname: Setsune
mesh_terms: D000447:Aldehydes / Q000737:chemistry; D000588:Amines / Q000737:chemistry*; D002942:Circular Dichroism; D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry; D018360:Crystallography, X-Ray; D007097:Imines / Q000737:chemistry*; D008968:Molecular Conformation; D009532:Nickel / Q000737:chemistry*; D011758:Pyrroles / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D000447:Aldehydes; D000588:Amines; D056831:Coordination Complexes; D007097:Imines; D011758:Pyrroles; D009532:Nickel
keywords: chirality; helical structures; metalation; oligopyrroles; porphyrinoids