Reactions of cobalt(ii) chloride and cobalt(ii) acetate with hemisalen-type ligands: ligand transformation, oxidation of cobalt and complex formation. Preliminary study on the cytotoxicity of Co(ii) and Co(iii) hemisalen complexes?

RSC Advances Pub Date: 2023-03-16 DOI: 10.1039/D2RA07089H

Abstract

Several molecular cobalt(II) complexes, one Co(II) coordination polymer and one ionic cobalt(III) complex with imine hemisalen ligands were synthesized. The hemisalen ligands were synthesized from o-vanillin (oVP) and diverse aminopyridines (compounds HL1–HL4) or aminophenol (compound HL5). It was observed that cobalt(II) chloride in dry acetonitrile catalyzes a transformation of HL1 and HL3 instead of complex formation. The conversion of these imines proceeded via self-cyclization to N-2′′-pyridyl-2,6-dioxo-9-aza-[c,g]di-2′-methoxybenzo nonan or its methyl derivative as the major product. The remaining reactions were performed using imines HL1–HL5 and cobalt(II) acetate Co(Ac)2 in methanol or DMSO/acetonitrile resulting in forming a series of cobalt complexes. The following series of compounds was obtained: two similar tetrahedral molecular Co(II) complexes [Co(L1)2] and [Co(L3)2], one trinuclear, mixed-ligand Co3(Ac)2(L4)2(oVP)2, one coordination polymer {Co(L2)2}∞ and finally one octahedral anionic Co(III) complex [HNEt3][Co(L5)3]. The latter complex formed in a cobalt(II) acetate reaction with a hemisalen HL5 derived from oVP and 2-aminophenol. The molecular structures of all compounds were confirmed by X-ray diffraction, and the cytotoxicity of Co(II) and Co(III) complexes towards cancer cell lines HCT116, HL-60 and normal cell line MRC-5 was studied.

Graphical abstract: Reactions of cobalt(ii) chloride and cobalt(ii) acetate with hemisalen-type ligands: ligand transformation, oxidation of cobalt and complex formation. Preliminary study on the cytotoxicity of Co(ii) and Co(iii) hemisalen complexes
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