Hydrothermal Synthesis, Crystal Structure and Electrochemical Properties of a 3D Supramolecular Compound: [Co2(Dpq)2(btec)(H2O)6]•2H2O

A new 3D supramolecular compound,[Co2(Dpq)2(btec)(H2O)6]·2H2O,was obtained from the hydrothermal reaction of cobalt(Ⅱ) nitrate with mixed ligands [1,2,4,5-benzenetetracarboxylate(btec) and dipyrido[3,2-d:2',3'-f]quinoxaline(Dpq)],and characterized by elemental analysis,IR,TG and single-crystal X-ray diffraction. The results reveal that the compound belongs to the monoclinic system with P21/c space group. The cell parameters are a=0.897 8(5) nm,b=2.982 2(16) nm,c=0.705 8(4) nm,β=94.199(6)°,V=1.884 8(18) nm3,Z=2,R1=0.035 0,wR2=0.079 6. The Co(Ⅱ) is coordinated with two nitrogen atoms of one Dpq molecule,one oxygen atom from the bridging ligand btec,and three oxygen atoms from coordinated water molecules,respectively,rendering a six-coordinate mode in a distorted octahedron geometry. Two adjaceut Co(Ⅱ) ions are linked by the bridging ligand btec to construct a dinuclear unit. The 3D supramolecular network of the title compound is formed through hydrogen bonds and π-π stacking interactions. Moreover,the electrochemical properties of carbon paste electrode modified by the compound(Co-CPE) were studied,and the results indicate that the Co-CPE exhibited one-electron redox wave in potential range of 600 to -300 mV due to the metal cobalt ion redox Co(Ⅱ)/Co(Ⅲ). The Co-CPE has good electrocatalytic activity toward the oxidation of nitrite in a 0.1 mol/L HAc-NaAc solution.