Hydrothermal synthesis of metal-organic frameworks based on aromatic polycarboxylate and flexible bis(imidazole) ligands

Via hydrothermal synthesis, the self-assembly of M(II) ions, H3BTC or H2NDC with three structure-related flexible bis(imidazole) ligands, L1, L2, and L3, generated six metal-organic polymers (M = Co, Ni, Zn; BTC = 1,3,5-benzenetricarboxylate, NDC = 1,2-benzenebicarboxylate, L1 = 1,4-bis(imidazol-1-ylmethyl)benzene, L2 = 1,1'-(1,4-butanediyl)bis(imidazole), L3 = 1,1'-(1,4-hexanediyl)bis (imidazole)): {Co-3(L1)(3)(BTC)(2)(mu-H2O)(3)center dot 2H(2)O}(n) (1), {Zn-2(L2)(HBTC)(2)center dot 2H(2)O}(n) (2), {Co(L3)(HBTC)}(n) (3), {Co(L1) (NDC)}(n) (4), {Ni(L2)(NDC)}(n) (5), and {Co(L3) (NDC)}(n) (6). The structure of 1 is the rare 4-connected self-penetrating metal-organic framework (MOF) with the (6(3))(2)(6(4).8(2))(2)(6(2).8(4)) topology notation; polymers 2 and 6 are two-dimensional (2D) (3,4)-connected and 4-connected nets, respectively. If the O-H center dot center dot center dot O/2.631 angstrom hydrogen bonds between HBTC2- dianions are not accounted for, then polymer 3 is a 2D (3,5)-connected net; contrarily, it is a pillar-layered three-dimensional supramolecular framework characterized by (4,5)-connected (4(2). 6(2).8(2))(4(2).6(8)) topology. 4 and 5 show 4-connected. MOFs with 6(5).10 and 6(5).8 CdSO4-type topology, respectively. Furthermore, their thermal properties are studied by thermogravimetric analysis.