Anion induced diversification from heptanuclear to tetranuclear clusters: Syntheses, structures and magnetic properties

Anion induced diversification from heptanuclear to tetranuclear clusters: Syntheses, structures and magnetic properties
来源：张淑华教授个人网站 2013-05-05

Three new polynuclear complexes, [Co7(bm)12]·(ClO4)2·13H2O (1), [Co4(bm)4Cl4(C3H7OH)4] (2), and [Co4(bm)4(μ-HCO2)2(μ2-HCO2)2 (C3H7OH)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 I41/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 {Co7} (1) and {Co4} (2) cores display dominant ferromagnetic interactions while the {Co4} (3) core displays dominant anti-ferromagnetic interactions.
[来源：中国聚合物网]