A One-Dimensional Double-Chain Co(II) Metal-Organic Framework Based on Mixed Flexible N-donor Carboxylate and Bipyridine Ligands: Synthesis, Structure, Thermal Stability and Magnetic Property

A new metal-organic framework (MOF), [Co(L)(2)(4,4-bipy)](n) (1) [HL=4-{[(1-phenyl-1H-tetrazol-5-yl)sulfanyl]methyl}benzoic acid, 4,4 '-bipy=4,4 '-bipyridine], has been solvothermally synthesized and characterized by single crystal X-ray diffraction, elemental analysis, infrared spectroscopy, thermogravimetric analysis, and powder X-ray diffraction. As revealed by the single crystal X-ray diffraction, there exist two kinds of the L- ligands that are Z-shaped and U-shaped L- ligands in complex 1. Two U-shaped L- ligands bridge two symmetry-related Co(II) cations to form a dinuclear [Co-2(COO)(2)] secondary building unit (SBU). The adjacent dinuclear SBUs are connected by bipillared 4,4 '-bipy ligands to generate an interesting one-dimensional double chain, which is further consolidated by the intrachain pi-pi interactions between neighbouring pyridyl rings of 4,4 '-bipy ligands. These one-dimensional double chains are further linked by multiple interchain C-HN, C-H pi and pi-pi weak interactions to form a three-dimensional supramolecular architecture. Thermogravimetric analysis and variable-temperature powder X-ray diffraction studies indicate that complex 1 shows good thermal stability. In addition, the magnetic investigation reveals that complex 1 exhibits an antiferromagnetic interaction between two Co(II) ions in the dinuclear [Co-2(COO)(2)] SBU.