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A series of 73 ligands and 73 of their Cu+2 and Cu+1 copper complexes with different geometries, oxidation states of the metal, and redox activities were synthesized and characterized. The aim of the study was to establish the structure-activity relationship within a series of analogues with different substituents at the N(3) position, which govern the redox potentials of the Cu+2/Cu+1 redox couples, ROS generation ability, and intracellular accumulation. Possible cytotoxicity mechanisms, such as DNA damage, DNA intercalation, telomerase inhibition, and apoptosis induction, have been investigated. ROS formation in MCF-7 cells and three-dimensional (3D) spheroids was proven using the Pt-nanoelectrode. Drug accumulation and ROS formation at 40-60 μm spheroid depths were found to be the key factors for the drug efficacy in the 3D tumor model, governed by the Cu+2/Cu+1 redox potential. A nontoxic in vivo single-dose evaluation for two binuclear mixed-valence Cu+1/Cu+2 redox-active coordination compounds, 72k and 61k, was conducted.

International audience; A novel approach to the synthesis of pH-sensitive prodrugs has been proposed: thiourea drug modification. Resulting prodrugs can release the cytotoxic agent and the biologically active 2-thiohydantoin in the acidic environment of tumor cells. The concept of acid-catalyzed cyclization of thioureas to 2-thiohydantoins has been proven using a FRET model. Dual prodrugs of model azidothymidine, cytotoxic doxorubicin, and 2-thiohydantoin albutoin were obtained, which release the corresponding drugs in the acidic environment. The resulting doxorubicin prodrug was tested on prostate cancer cells and showed that the thiourea-modified prodrug is less cytotoxic (average IC50 ranging from 0.5584 to 0.9885 μM) than doxorubicin (IC50 ranging from 0.01258 to 0.02559 μM) in neutral pH 7.6 and has similar toxicity (average IC50 ranging from 0.4970 to 0.7994 μM) to doxorubicin (IC50 ranging from 0.2303 to 0.8110 μM) under mildly acidic conditions of cancer cells. Cellular and nuclear accumulation in PC3 tumor cells of Dox prodrug is much higher than accumulation of free doxorubicin.

We have synthesized and characterized a panel of new binuclear mixed valence Cu(I,II) complexes containing substituted 2-alkylthio-5-arylmethylene-4H-imidazolin-4-ones with unusual structure. These complexes are shown to be cytotoxic for various cell lines. We have found that these compounds did not intercalate DNA, inhibited number of polymerases (telomerase predominantly), accumulated in the cell nucleus, and caused DNA degradation. Preliminary studies revealed that lead compound inhibited human breast adenocarcinoma growth in mice model.

The new tridentate organic N2S-type ligand, (4Z)-1-(2-azidoethyl)-4-[(pyridin-2-yl)-methylidene]-2-thioxoimidazol-5(4H)-one (LH), was synthesized. The reaction of LH with copper(II) chloride in a CH2Cl2/MeOH mixture afforded the coordination compound of the composition L2Cu2Cl (3). The crystal structure of 3 was solved and refined from X-ray powder diffraction data. Complex 3 has a binuclear structure with a short interatomic Cu-Cu distance and one bridging chlorine atom, which is located almost symmetrically with respect to both metal atoms. The planar organic ligands are noncoplanar and are at an angle of 53.56(1)° to each other.

A series of 2-aminosubstituted (5Z)-3-phenyl-5-(pyridine-2-ylmethylene)-3,5-dihydro-4H-imidazole-4-ones (L) was prepared by the reaction of the corresponding 2-alkylthio-3,5-dihydro-4H-imidazole-4-ones with morpholine or piperidine in the presence of ytterbium(III) triflate. The resulting ligands were subsequently reacted with CuCl2·2H2O and CoCl2·6H2O to give the corresponding copper(II) and cobalt(II) complexes, respectively. Analysis revealed that the complexes were formed with an LMCl2 (M = Cu, Co)-type composition in all cases. The structures of the three cobalt complexes prepared in this way were determined by X-ray crystallography. The results revealed that the cobalt ions in these complexes were tetrahedrally coordinated to two chloride anions and two nitrogen atoms from the pyridine and imidazole moieties of the ligand. The electrochemical properties of the ligands and their complexes were evaluated by cyclic voltammetry, and the results revealed that the first stage in the reduction of the Co(II) and Cu(II) complexes involved the reversible formation of the corresponding Co(I) and Cu(I) complexes, respectively. The cytotoxicity activities of the organic ligands and their complexes were evaluated against several cancer cell lines, including MCF-7, A549 and HEK293 cells. The copper complexes of the organic ligands bearing a phenyl or allyl moiety at their N(3) position together with a piperidine substituent at the 2-position of their imidazolone ring exhibited the greatest cytotoxicity of all of the compounds tested in the current study. Keywords: Cobalt(II) complexes, Copper(II) complexes, 2-Aminoimidazole-4-ones, Cytotoxicity