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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.

Magdalena SiedzielnikMonika PawłowskaMateusz DaśkoHubert KleinschmidtAnna Dołęga
Published in: RSC advances (2023)
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 ( o VP) 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 Co 3 (Ac) 2 (L4) 2 ( o VP) 2 , one coordination polymer {Co(L2) 2 } ∞ and finally one octahedral anionic Co(iii) complex [HNEt 3 ][Co(L5) 3 ]. The latter complex formed in a cobalt(ii) acetate reaction with a hemisalen HL5 derived from o VP 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.
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