Synthesis and structure of a new organic-inorganic framework with tetranuclear clusters, [Co4(OH)2(H2O)2](C4H11N2)2[C6H2(COO)4]2•3H2O

A new hybrid organic-inorganic three-dimensional compound, [Co-4(OH)(2)(H2O)(2)](C4H11N2)(2)[C6H2(CO2)(4)](2).3H(2)O 1, has been synthesized via hydrothermal reactions and characterized by single-crystal X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, and magnetic techniques. Compound 1 crystallizes in the monoclinic space group P2(1)/n (no. 14) with a =: 6.3029(9) Angstrom, b = 16.413(2) Angstrom, c = 17.139(2) Angstrom, beta = 98.630(2)degrees, V= 1735.0(4) Angstrom(3), Z = 2. Compound 1 contains tetranuclear Co-4(mu(3)-OH)(2)(H2O)(2) clusters that are inter-linked by pyromellitate bridging ligands into a three-dimensional structure containing one-dimensional tunnels along the a-axis with water and pendant monoprotonated piperazine molecules in the center. The variable temperature magnetic susceptibility was measured from 2 to 300 K at 5000 Oe showing a predominantly anti-ferromagnetic interaction in 1, and the field dependence of magnetization was measured at 2, 5, 15, and 20 K indicating the competition of magnetic interactions in the tetranuclear centers. (C) Elsevier Science (USA).