New BI and TRI-Thiazole copper (II) complexes in the search of new cytotoxic drugs against breast cancer cells

Abstract New thiazolyl derivatives (BT and TT) and their copper (II) complexes [Cu2Cl2(BT)2] (Cu-BT) and [Cu4ClO2(TT)2]PF6⋅3.5H2O (Cu-TT) were synthesized and characterized by elemental analysis, 1H NMR and 13C NMR, HRMS, X-ray diffraction, IR and UV–Vis spectroscopies. The crystal structure of Cu-BT shows the formation of a dinuclear complex where each copper(II) center is bonded to two thiazol N atoms, from different BT ligands, one deprotonated amide N atom, an O atom from the ester terminal groups and a chlorine atom. The structure found for Cu-TT is a positively charged tetranuclear moiety containing two deprotonated TT ligands, a chlorine anion, two hydroxide anions acting as bridges between the copper centers and a water molecule. The cytotoxic activity of both copper complexes was evaluated on metastatic breast cancer cell lines, characterized for its rapidly dividing behavior. Both, Cu-BT and Cu-TT, show higher cytotoxic activity against these tumor cells than free BT and TT and also than cisplatin. In addition, we found that both complexes interact with DNA. Consistently, they also show cytotoxicity against a rapidly dividing non-tumor cell line, although with higher IC50, being such interaction and selectivity an indicator of the possible coexistence of more than one mechanism of action.