title: Anion induced diversification from heptanuclear to tetranuclear clusters: syntheses, structures and magnetic properties.
abstract: Three new polynuclear complexes, [Co(7)(bm)(12)]·(ClO(4))(2)·13H(2)O (1), [Co(4)(bm)(4)Cl(4)(C(3)H(7)OH)(4)] (2), and [Co(4)(bm)(4)(μ-HCO(2))(2)(μ(2)-HCO(2))(2)(C(3)H(7)OH)(2)] (3) (Hbm = (1H-Benzimidazol)-methanol), have been synthesized and characterized by elemental analysis, IR, powder X-ray diffraction and X-ray single-crystal diffraction. Compound 1 features a centrosymmetric wheel-like heptanuclear Co(II) cluster. Compound 2 having a I4(1)/a space group exhibits a tetranuclear Co(II) cluster with a cubane topology in which the central Co(II) ion and oxygen atoms from bm occupy the alternate vertices of the cube. However, compound 3 has a tetranuclear Co(II) cluster with a C2/c space group different from that of compound 2. These results show that the geometries and sizes of the corresponding anions as well as their coordinating and hydrogen-bonding properties are essential in determining the final structures of the assemblies. Magnetic properties of 1-3 in the 2-300 K have also been discussed. The {Co(7)} (1) and {Co(4)} (2) cores display dominant ferromagnetic interactions while the {Co(4)} (3) core displays dominant anti-ferromagnetic interactions.
authors.affiliation: School of Chemistry and Chemical Engineering, (State Key Laboratory Cultivation Base for the Chemistry and Molecular Engineering of Medicinal Resources, Ministry of Science and Technology of China), Guangxi Normal University, Guilin, 541004, People's Republic of China.
authors.forename: Shu-Hua
authors.initials: SH
authors.lastname: Zhang
authors.forename: Lu-Fang
authors.initials: LF
authors.lastname: Ma
authors.forename: Hua-Hong
authors.initials: HH
authors.lastname: Zou
authors.forename: Yin Guang
authors.initials: YG
authors.lastname: Wang
authors.forename: Hong
authors.initials: H
authors.lastname: Liang
authors.forename: Ming Hua
authors.initials: MH
authors.lastname: Zeng
mesh_terms: D000838:Anions / Q000737:chemistry; D003035:Cobalt / Q000737:chemistry*; D007501:Iron / Q000737:chemistry; D060328:Magnetic Phenomena; D059346:Magnets; D015394:Molecular Structure; D013055:Spectrophotometry, Infrared; D017550:Spectroscopy, Fourier Transform Infrared; D014961:X-Ray Diffraction
chemical_list: D000838:Anions; D003035:Cobalt; D007501:Iron