A Metal-organic Framework with Paddle-wheel Zn2(CO2)4 Secondary Building Units and Cubane-1,4-dicarboxylic Acid Linkers

A new crystal structure of catena-(bis((mu(4)-cubane-1,4-dicarboxylato)-(N-methyl-2-pyrrolidone)-zinc(II)) N-methyl-2-pyrrolidone solvate) (1) was prepared by solvothermal method. The crystal structure of the compound was analyzed by single-crystal X-ray diffraction. It has a P (1) over bar space group, with lattice parameters a = 10.7190(4) angstrom, b = 10.8245(5) angstrom, c = 10.8403(8) angstrom, a = 80.291(5)degrees, beta = 70.0015(5)degrees, gamma = 77.531(4)degrees, V = 1147.97(12) angstrom(3). The secondary building units of 1 consist of 2 central Zn ions, coordinated by 4 carboxylate groups in a bis-monodentate way, forming a square planar configuration of Zn-2(CO2)(4), known as paddle-wheel units. The paddle-wheels are connected by cubane-1,4-dicarboxylic acid linkers at the edges, resulting in a two-dimensional coordination polymer with a square lattice (sql) underlying network topology. The axial sites of the zinc atoms are occupied by N-methyl-2-pyrrolidone molecules. In this new crystal structure the two-dimensional polymer planes are interstacked by weak dispersion bonds. The axial N-methyl-2-pyrrolidone solvent molecules determine the distances of planar polymer planes. The thermal properties of this new structure were studied by thermogravimetry/mass spectrometry in inert atmosphere. It was found, that the organic linkers in the framework structure do not decompose below 200 degrees C. The stochiometry of the activated compound is Zn-2(C8H6(COO)(2)](2)(C5H9NO)(2), as determined by thermogravimetry in oxidative atmosphere.