Functionalized and mixed metal -organic frameworks.

Abstract

Novel extended transition metal-organic frameworks have been prepared. The synthesis, characterization, and crystal structures of each compound is described. The reaction of cobalt sulfate pentahydrate with benzene triearboxylic acid demonstrates an alternative method for making MOF-0, a layered two-dimensional extended network. In addition to cobalt, analogous compounds are shown with nickel, magnesium, iron, manganese, and cadmium. Mixing of nickel and cobalt in different ratios shows that mixed metal frameworks can be tailored with controlled metal ion stoichiometry. Functionalization of the organic ligand using amino, hydroxy, and halogen functionality has been demonstrated. The reaction of 2-aminoterephthalic acid and zinc nitrate hexahydrate at room temperature yielded orange crystals of Zn(C₆H₅O₄N)(DMF)₁(ClC₆H₅)_0.25 having the space group C2/m. The reaction of 2,5-dihydroxyterephthalic acid and copper nitrate hemihexahydrate at room temperature yielded Cu(C₆H₄O₆)(DMF)₂ crystallizing in the space group P2(1)/c, while the reaction of the same ligand with magnesium sulfate yielded Mg(O₂C₆O₂H₄O₂)(DMF)₂ in the space group C2/c. A halogenated aromatic, 2,3,5,6 tetrafluoroterephthalic acid, and copper nitrate hemihexahydrate yielded crystals of Cu₄O₃(O₂C₆F₄O₂)(DMF)₅(ClC₆H₅)₁(C₃H₅OH)₁(H₂O)₅ in the space group P2₁/n. The synthesis of three-dimensional porous metal formates has been demonstrated by reacting magnesium nitrate hexahydrate with two equivalents of formic acid. The analogous compound with iron has been demonstrated using iron (II) chloride hexahydrate with two equivalents of formic acid. Both crystallize in the space group P2₁/n. The synthesis and properties of three isostructural three-dimensional terbium frameworks Tb(O₂C₁₆H₈O₂)_1.5(DMF)₃, Tb(O₂B₁₀H₁₀O₂)_1.5(DMF)₂(H₂O)₂, Tb(O₂C₆O₂H₄O₂)_1.5(DMF)₃, are presented. Each network reveals a dinuclear [Tb(L)_1.5(DMF)₁]₂ (L = O₂C₁₆H₈O₂, O₂B₁₀H₁₀O₂, O₂C₆O₂H₄O₂) complex which incorporates two bridging carboxylates, and one non-bridging carboxylate. All three compounds crystallize in the space group P(-1). The reaction of pentaerythritol with titanium isopropoxide in a solution of pyridine at room temperature yielded colorless plates, which was formulated as Ti₈[C(CH₂O)₄]₄[OCH(CH₃)₂]₁₆. The single crystal structure analysis revealed a dimer in the unit cell of the triclinic space group P1¯.