Synthesis and physicochemical properties of some transition metal complexes with 3-hydroxypyridine

The complexes ML2·2H2O and CrL 3·8H2O were synthesized by the reaction of Cu(II), Ni(II), Co(II), Cd(II), and Cr(III) nitrates with 3-hydroxypyridine (HL) and identified. The spectroscopic characteristics of neutral, anionic, and cationic forms of the ligand were determined. It was shown that 3-hydroxypyridine enters the complex as an anion to give polymeric chains due to the ligand coordination through the N and O atoms. Complexation of copper, cobalt, and chromium nitrates with 3-hydroxypyridine in ethanol solutions was studied, and the formation constant of the copper complex was calculated. It was found that Cu(II) and Cr(III) complexes are formed in the solid state and in solutions (M: L = 1:2 and 1:3, respectively; in the case of Cu(II), the M:L ratio is 1:3)