Synthesis of cobalt(III) complexes with new oxime-containing Schiff base ligands and metal-ligand coordination in solution

Cobalt(III) complexes with new oxime-containing Schiff base ligands: 2-hydroxyimino-N′-[1-(2-pyridyl)ethylidene]propanohydrazone (Hpop) and 2-hydroxyimino-N′-[(pyridine-2-yl)methylidene]propanohydrazone (Hpoa) reveal high efficacy in the coordination of Co(II) ions followed by auto-oxidation to Co(III) under O2. Differences in complexing ability are attributed to the presence of the -CH3 substituent in Hpop (instead of H in Hpoa) at the ethylidene carbon close to the hydrazone N atom, which influences the flexibility of the propanohydrazide chain, essential in chelate formation.