The present study aims at synthesizing three new copper(II) complexes of maltol in the presence of 1,10-phenanthroline-, 2,20 -bipyridine- and 4,4-dibromo-2,20 -bipyridine ligands. The structure of the Cu(II) complexes was characterized by FTIR, CHN analysis and X-ray crystallography. The interaction of the Cu(II) complexes with human serum albumin (HSA) was studied using various methods including fluorescence spectroscopy, UV-visible spectroscopy and molecular docking. The cytotoxic activity of the complexes was investigated using human breast cancer cells (MCF-7), and the results were compared with the activity of cis-platin as a positive control. The data showed that the complex 1, [Cu(mal)(4,4- dibromo-2,20 -bpy)(H2O)]NO3, has the highest cytotoxicity among the compounds. The experiment indicated that the quenching process of HSA fluorescence by complexes 1–4 and the maltol ligand is a static mechanism. In addition, the results provided information about thermodynamic parameters and the number of binding sites. The high values of Kb show that the complexes can bind strongly with HSA. The results from the UV-Visible spectroscopy studies demonstrated that conformational alterations occurred in the secondary structure of HSA due to binding with the complexes.

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