Synthesis, Crystal Structure, and Thermal Decomposition of the Cobalt(II) Complex with 2-Picolinic Acid

Abstract

The cobalt(II) complex of 2-picolinic acid (Hpic), namely,[Co(pic)2(H2O)2]·2H2O, was synthesized with the reaction of cobalt acetate and 2-picolinic acid as the reactants by solid-solid reaction at room temperature. The composition and structure of the complex were characterized by elemental analysis, infrared spectroscopy, single crystal X-ray diffraction, and thermogravimetry-differential scanning calorimetry (TG-DSC). The crystal structure of the complex belongs to monoclinic system and space groupP2(1)/n, with cell parameters ofa=9.8468(7) Å,b=5.2013(4) Å,c=14.6041(15) Å,β=111.745(6)°,V=747.96(11) Å3,Z=2,Dc=1.666 g cm−3,R1=0.0297, andwR2=0.0831. In the title complex, the Co(II) ion is six-coordinated by two pyridine N atoms and two carboxyl O atoms from two 2-picolinic acid anions, and two O atoms from two H2O molecules, and forming a slightly distorted octahedral geometry. The thermal decomposition processes of the complex under nitrogen include dehydration and pyrolysis of the ligand, and the final residue is cobalt oxalate at about 450°C.