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

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.