Oxidized cobalt complexes of salicylaldehydes

Cobalt(III) complexes of 2,2′-dipyridylamine (dpamH) and the ligands salicylaldehyde (X-saloH) and their corresponding salicylic acids (X-salicylato), where X = CH3, Cl and Br, under the general formula [Co(X-salo)(X-salicylato)(dpamH)] (1–3), were synthesized in situ by slow oxidation in air of ethanolic solutions of the complexes [Co(5-X-salo)2(dpamH)]. The new compounds were characterized by physicochemical methods and by spectroscopy (IR, 1H-NMR and UV–Vis). The octahedral geometry around Co3+ ion and the bidentate chelating mode of the salicylaldehydato anion (X-salo−) and the salicylato di-anion (X-salicylato2−) were proved by single-crystal X-ray diffraction analysis for the complex [Co(5-CH3-salo)(5-CH3-salicylato)(dpamH)] (1). The variable-temperature (76–303 K) magnetic susceptibility measurements showed a diamagnetic nature of the complexes, in accordance with their molecular structure. The simultaneous TG/DTG–DTA technique was used to analyze their thermal behavior under inert and/or oxygen atmosphere, with particular attention to determine their thermal degradation pathways, which was found to have a multi-step nature, accompanied by the release of the ligand molecules.