A series of nine copper complexes were synthesized by reacting 1,3-disubstituted thioureas with copper(II) chloride. The new compounds were characterized by elemental analysis, infrared, ultraviolet-visible and X-ray absorption spectroscopies as well as molecular modelling. The molecular structure of complexes in the solid state consists of two thiourea ligands chelated to the Cu(II) ion through the S and deprotonated N atoms (CuN2S2). The coordination polyhedron of metal cation in powdered samples exhibits two different geometries. Pseudo-tetrahedral structure is observed for noncentrosymmetric complexes with cis-N2S2 arrangement around Cu(II). A distorted square planar geometry is characteristic for centrosymmetric compounds with trans arrangements of chelating atoms around the central ion. All complexes after dissolving in dimethyl sulfoxide adopt a centrosymmetric coordination, while after diluting this solution with water, the reorganization of atoms around the metal cation is observed, leading to the formation of a tetrahedral compounds. Initial ligands and Cu(II) complexes were evaluated for their cytotoxicity. Two complexes with 4- and 3-bromophenyl attached to the (1,7,8,9,10-pentamethyl-3,5-dioxo-4-azatricyclo[5.2.1.02,6]dec-8-en-4-yl)thiourea moiety (Cu1, Cu3) are cytotoxic against SW480 and PC3 cells (IC50 4-19 μm), and non-cytotoxic against HaCaT cells (IC50 ≥ 84 μm), being more selective than doxorubicin and cisplatin used as references. The compounds induced apoptosis in cancer cells, however, Cu3 was estimated to be highly active inducer of late apoptosis in SW480 and PC3 cells at lower toxicity against normal cells. The likely mechanism of action of complexes is correlated with decreasing release of IL-6 in cancer cell lines.
Keywords: ATR-IR; Anticancer activity; Cu(II) complexes; Thiourea derivative; UV–Vis; XAFS.
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