Solid–Solid Synthesis, Crystal Structure and Thermal Decomposition of Copper(II) Complex of ۲-Picolinic Acid

The copper(II) complex [Cu(pic)۲]·۲H۲O was synthesized with ۲-picolinic acid (Hpic) and copper acetate as reactants by room temperature solid-solid reaction. The composition and structure of the complex was characterized by elemental analyses, single crystal X-ray diffraction, X-ray powder diffraction, FT-IR spectroscopy and thermogravimetry-differential scanning calorimetry. The crystal structure of the copper(II) complex belongs to triclinic system and space group , with cell parameters of a = ۵.۱۲۷۴(۱۶) Å, b = ۷.۶۴۱(۲) Å, c = ۹.۲۰۹(۲) Å,α = ۷۴.۹۱(۲)°, β = ۸۴.۵۶(۲)°, γ = ۷۱.۵۸(۳)°, V = ۳۳۸.۴۸(۱۵) Å۳, Z = ۱, F(۰۰۰) = ۱۷۵, R۱ = ۰.۰۵۳۰, and wR۲ = ۰.۱۱۴۱. The Cu(II) ion is six-coordinated through two nitrogen atoms from two pyridine rings and four carboxyl oxygen atoms from four different ۲-picolinic acid anions, forming an elongated octahedral geometry. The interaction of carboxylate O and Cu(II) forms an one-dimensional chain structure, and the complex exhibits a two-dimensional layered structure by hydrogen bonds. The thermal decomposition processes of the complex under air include dehydration and pyrolysis of the ligand, and the final residue at about ۴۰۰ °C is copper oxide.

Keywords:

۲-Picolinic acid , Copper(II) complex , Room temperature solid-solid reaction , Crystal structure , Thermal decomposition