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

Abstract EN

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) Å, b = 5.2013 (4) Å, c = 14.6041 (15) Å, β = 111.745 (6)°, V = 747.96 (11) Å3, 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.