Cobalt(II) and copper(II) covalently and non-covalently dichlorido-bridged complexes of an unsymmetrical tripodal pyrazolyl-pyridyl amine ligand: Structures, magnetism and cytotoxicity

• Dinuclear Co(II) and mononuclear Cu(II) complexes were prepared using a tripodal ligand.
• Bis(3,5-dimethyl-1H-pyrazol-1-yl-methyl)(2-pyridylmethyl)amine was utilized as the ligand.
• Co(II) complex revealed weak ferromagnetic exchange, axial anisotropy and slow relaxation of magnetization.
• The in vivo cytotoxicity against MCF7 and HeLa human cancer cell lines were also examined.

The reaction of a methanolic solution containing MIICl2 (M = Co or Cu) with bis(3,5-dimethyl-1H-pyrazol-1-yl-1-ethyl)(2-pyridylmethyl)amine (bedmpzp) in the presence of NH4PF6 afforded the dinuclear doubly bridged-dichlorido complex [Co2(bedmpzp)2(μ-Cl)2](PF6)2 (1) and the mononuclear [Cu(bedmpzp)Cl]PF6 (2) one. The complexes were structurally and magnetically characterized. The weak ferromagnetic exchange and the axial type of magnetic anisotropy found in 1 is associated with slow relaxation of magnetization as revealed by AC susceptibility measurements. This finding puts 1 into a class of polynuclear single-molecule magnets based on 3d metals. X-ray structure of 2 revealed mononuclear nature of the complex, forming supramolecular dimers in the solid state. The non-covalent interactions of the Cu⋅⋅⋅Cl type present in its crystal structure induced a weak antiferromagnetic exchange. The results of magnetic analysis were also supported by DFT and CASSCF/NEVPT2 calculations. The in vitro cytotoxicity of the complexes against MCF7 and HeLa human cancer cell lines were also tested. The best cytotoxicity was achieved for complex 2 on HeLa, with IC50 = 2.5(0.9) μM.

The dinuclear doubly bridged-dichlorido complex [Co2(bedmpzp)2(μ-Cl)2](PF6)2 (1) and the mononuclear [Cu(bedmpzp)Cl]PF6 (2) were structurally and magnetically characterized. Complex 1 revealed weak ferromagnetic exchange with slow relaxation of magnetization, whereas 2 showed weak antiferromagnetic exchange. The in vitro cytotoxicity of the complexes against MCF7 and HeLa human cancer cell lines were also tested.Figure optionsDownload as PowerPoint slide