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

摘要

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) have been investigated. The crystal and the molecular structure of 2[Co(pop) _2]Br·3CH _3OH·0.5H _2O (1) has been determined using single-crystal X-ray diffraction methods. Electrospray ionization mass spectrometry confirmed the presence of polynuclear complexes with Co(II). The potentiometric and spectrophotometric results in 10/90 (v/v) DMSO/water solution reveal that both of the oxime-containing Schiff base ligands show a very high efficacy in the coordination of Co(II) ions. As it has been indicated, the difference between the two ligands in their complexing ability may be attributed to the presence of the methyl group in Hpop and by the steric interaction during chelate formation. The experiments in solution were carried out under an inert atmosphere since in both cases the complexes are capable of dioxygen uptake, followed by irreversible oxidation to Co(III) complexes.