title: A novel alpha-helix-liked metallohelicate series and their structural adjustments for the isomorphous substitution.
abstract: A novel metallohelical motif is well designed and synthesized by mimicking the alpha-helical fold structure of protein. The 1D helical structures of [Cd(CH2(COO)2)(SC(NH2)2)2]n (I) and [Zn(CH2(COO)2) (SC(NH2)2)2]n (II) are primarily induced and stabilized by the multiple long-range intrahelix hydrogen bonds. Malonate dianion acts as a bidentate ligand coordinated with metal ions to form the backbone of the helix, and thiourea molecules that bend into the helical turn are involved in the intrahelix hydrogen-bond system. The metal ion occupations in the helix of I and II can be freely substituted by simply controlling the initial ratio of those two metal ions. Single crystals of three mixed metal ion complexes of [Cd0.77Zn0.23(CH2(COO)2)(SC(NH2)2)2]n (III), [Cd0.50Zn0.50(CH2(COO)2)(SC(NH2)2)2]n (IV), and [Cd0.21Zn0.79(CH2(COO)2)(SC(NH2)2)2]n (V) were synthesized from systems with an initial Cd/Zn mole ratio of 1:1 for III, 1:2 for IV, and 1:8 for V. They are isomorphous as confirmed by X-ray characterization. When the metal ion is substituted, the multiple intrahelix hydrogen interaction motifs of the coordination polymer structure are self-adjusted to sustain their 1D helical motifs.
authors.affiliation: Department of Chemistry, Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, P. R. China.
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.forename: J
authors.initials: J
authors.lastname: Li
authors.forename: J
authors.initials: J
authors.lastname: Chen
authors.forename: Q
authors.initials: Q
authors.lastname: Su
authors.forename: W
authors.initials: W
authors.lastname: Deng
authors.forename: M
authors.initials: M
authors.lastname: Nishiura
authors.forename: T
authors.initials: T
authors.lastname: Imamoto
authors.forename: X
authors.initials: X
authors.lastname: Wu
authors.forename: Q
authors.initials: Q
authors.lastname: Wang