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A trimetallic CuII derivative, [Cu3(L)2(CF3COO)2] (1) (where H2L = N,N′-bis(salicylidene)-1,3-propanediamine), was prepared and characterized. In 1, the two terminal CuII ions are linked to the central CuII by trifluoroacetato and doubly bridging phenoxido. Both the square-pyramidal and octahedral geometries are observed among two different CuII centers in the linear arrangement of the trimetallic unit. Compound 1 is characterized by IR and UV-Vis spectra. Compound 1 has high cytotoxic activity in breast adenocarcinoma (MCF-7), colorectal carcinoma (HCT116) and particularly, in ovarian carcinoma (A2780) cell line compared to a lung adenocarcinoma cell line. The IC50 in A2780 cells is 25 times lower than the respective value for normal human primary fibroblasts demonstrating 1 has higher cytotoxicity towards cancer cells. Additionally, combination of DOX with 1 induces a higher loss of HCT116 cell viability compared with each drug alone.

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To investigate the effect of different halogen substituents and leaving groups and the flexibility of ligands on the anticancer activity of copper complexes, sixteen copper(ii) complexes with eight different tridentate Schiff-base ligands containing pyridine and 3,5-halogen-substituted phenol moieties were synthesized and characterized by spectroscopic methods. Four of these complexes were also characterized by X-ray crystallography. The cytotoxicity of the complexes was determined in three different tumor cell lines (i.e. the A2780 ovarian, HCT116 colorectal and MCF7 breast cancer cell line) and in a normal primary fibroblast cell line. Complexes were demonstrated to induce a higher loss of cell viability in the ovarian carcinoma cell line (A2780) with respect to the other two tumor cell lines, and therefore the biological mechanisms underlying this loss of viability were further investigated. Complexes with ligand L-1 (containing a 2-pycolylamine-type motif) were more cytotoxic than complexes with L-2 (containing a 2-(2-pyridyl)ethylamine-type motif). The loss of cell viability in A2780 tumor cells was observed in the order Cu(Cl-2-L-1)NO3 > Cu(Cl-2-L-1)Cl > Cu(Br-2-L-1)Cl > Cu(BrCl-L-1)Cl. All complexes were able to induce reactive oxygen species (ROS) that could be related to the loss of cell viability. Complexes Cu(BrCl-L-1)Cl and Cu(Cl-2-L-1)NO3 were able to promote A2780 cell apoptosis and autophagy and for complex Cu(BrCl-L-1)Cl the increase in apoptosis was due to the intrinsic pathway. Cu(Cl-2-L-1)Cl and Cu(Br-2-L-1)Cl complexes lead to cellular detachment allowing to correlate with the results of loss of cell viability. Despite the ability of the Cu(BrCl-L-1)Cl complex to induce programmed cell death in A2780 cells, its therapeutic window turned out to be low making the Cu(Cl-2-L-1)NO3 complex the most promising candidate for additional biological applications.