Syntheses, topological analyses and magnetic properties of two 3D supramolecular nickel-organic frameworks constructed from 1,3,5-benzenetricarboxylate and flexible imidazole-based ligands

Two supramolecular nickel-organic frameworks, [Ni(HBTC)(bix)](n) (1) and [Ni-3(BTC)(2)(mbix)(3)(H2O)(4)](n) center dot 6nH(2)O (2) (bix = 1,4-bis(imidazole-1-yl-methyl)benzene, mbix = 1,3-bis(imidazole-1-yl-methyl)benzene, and H3BTC = 1,3,5-benzenetricarboxylate), have been hydrothermally prepared by the assembly of H3BTC, Ni2+ with bix or mbix. Compound 1 shows a 2D layer structure, whose 3D supramolecular structure exhibits a fsc topology when hydrogen-bonging interactions between the adjacent layers are taken into account. Compound 2 manifests an unprecedented 2D (3, 4)-connected topological net. The 3D supramolecular framework of 2 is formed through pi center dot center dot center dot pi stacking interactions between the adjacent layers. The magnetic studies show that 1 features overall ferromagnetic property whilst 2 presents strong zero-field splitting (ZFS) when treated as a mononuclear model. Furthermore, the IR and TGA properties of 1 and 2 were also studied. (C) 2009 Elsevier B.V. All rights reserved.