A three-dimensional highly stable cobalt(II) metal-organic framework based on terephthalic acid: synthesis, crystal structure, thermal and physical properties

A metal-organic framework complex, [Co(mu(3)-tp)(mu(2)-pyz)] (n) , where H(2)tp = 1,4-benzenedicarboxylic acid (terephthalic acid) and pyz = pyrazine, has been synthesized under hydrothermal conditions and characterized by physico-chemical and spectroscopic methods, thermogravimetric analysis and single-crystal X-ray diffraction. Each Co(II) center is surrounded by four carboxylate oxygen atoms from three tp ligands and two nitrogen atoms from two pyrazine ligands, giving a distorted octahedral geometry. The entire framework is made up of two-dimensional sheets of dicobalt ions linked via terephthalate ligands to form rectangles. The sheets are then linked into each other via the axial pyrazine ligands, forming an interlocked 3-D network, which is finally arranged as an ABAB interconnected pattern. Photoluminescence measurements for the polymer in the solid state show an emission at 414 nm, which suggests this complex as a potential blue-light material. The electrochemical behavior of a modified carbon paste electrode prepared from the complex has been studied by cyclic voltammetry, indicating quasi-reversible redox behavior.