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 (H 2 O) 2 ] · 2 H 2 O, 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 group P 2 (1) / n, with cell parameters of a = 9.8468 (7), b = 5.2013 (4), c = 14.6041 (15), β = 111.745 (6)°, V = 747.96 (11)3, Z = 2, D c = 1.666 g cm-3, R 1 = 0.0297, and w R 2 = 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. © 2014 Di Li and Guo-Qing Zhong.