Hydrothermal syntheses, structural characterizations, and magnetic properties of five MOFs assembled from C2-symmetric ligand of 1,3-di(2′,4′-dicarboxylphenyl)benzene with various coordination modes

Five new complexes, namely, [Ni(H2DDB)(H2O)(2)(mu(2)-H2O)](n) (1), [Ni-1.5(DDB)(1,4-bib)(1.5)(H2O)](n) (2), {[Ni-2(DDB)(1,3-bib)(2)(mu(2)-H2O)]center dot 2H(2)O}(n) (3), [Cu-2(H2DDB)(2)(1,4-bib)(2)]center dot H2O (4), and {[Cu-1.5(HDDB)(1,2-bimb)]center dot H2O}(n) (5), have been synthesized using the solvothermal reaction of 1,3-di(2',4'-dicarboxylphenyl) benzene (H4DDB) with nickel(II) or copper(II) salts in the presence of ancillary ligands of bis(imidazole) linkers (1,4-bib = 1,4-bis(1H-imidazol-4-yl)benzene, 1,3-bib = 1,3-bis(1H-imidazol-4-yl)benzene, and 1,2-bimb = 1,2-bis(imidazol-1-ylmethyl)benzene). Their structures have been determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectroscopy, powder X-ray diffraction (PXRD), and thermogravimetric (TG) analyses. In complex 1, Ni-II ions are bridged by associated water molecules to form an interesting [Ni(H2DDB)(H2O)(2)(mu(2)-H2O)](n) chain structure, which is further extended to a 3D supramolecular structure via the hydrogen bonds. In complex 2, a novel 3D (3,3,6)-connected (6(3))(4)(6(5)center dot 8(8)center dot 10(2)) net is generated from the synergistic effect of 1D [Ni(1,4-bib)](n) zigzag chains and 2D [Ni-3(DDB)(2)](n) bilayers. For complex 3, with the employment of 1,3-bib bis(imidazole) linker instead of 1,4-bib, an unprecedented binuclear {Ni-2(COO)(mu(2)-H2O)} SBUs based 3D (3,6)-connected (3 center dot 6 center dot 7)(3(2)center dot 4(3)center dot 5(4)center dot 6(3)center dot 7 center dot 8(2)) net was obtained. Furthermore, when NiII ions were replaced by Cu-II ions, a paddle wheel {Cu-2(COO)(4)} SBUs based [Cu-2(H2DDB)(1,4-bib)(2)] (4) complex was formed. For complex 5, 2D [Cu-3(HDDB)(2)](n) sheets are further linked by 1,2-bimb pillars to expand a paddle wheel {Cu-2(COO)(4)} SBUs based 3D architecture with 4-connected (6(5) 8)-cds topology. Moreover, the magnetic properties of 1, 3, and 5 have been investigated.