Synthesis, Characterization, and Biological Evaluation of Some 3d Metal Complexes with 2-Benzoylpyridine 4-Allylthiosemicarbazone

The eight new copper(II), nickel(II), zinc(II), and iron(III) coordination compounds [Cu(L)Cl]2 (1), [Cu(L)Br]2 (2), [Cu(L)(NO3)]2 (3), [Cu(phen)(L)]NO3 (4), [Ni(HL)2](NO3)2·H2O (5), [Ni(HL)2]Cl2 (6), [Zn(L)2]·0.125H2O (7), and [Fe(L)2]Cl (8), where HL stands for 2-benzoylpyridine 4-allylthiosemicarbazone, were synthesized and characterized. 1H, 13C NMR, and FTIR spectroscopies were used for characterization of the HL thiosemicarbazone. The elemental analysis, the FTIR spectroscopy, and the study of molar electrical conductivity were used for characterization of the coordination compounds 1–8. Also, the crystal structures of HL, its salts ([H2L]Cl; [H2L]NO3), and complexes 1, 3, 5, 7, and 8 were determined using single-crystal X-ray diffraction analysis. Complexes 5, 7, 8 have mononuclear structures, while copper(II) complexes 1 and 3 have a dimeric structure with the sulfur atoms of the thiosemicarbazone ligand bridging two copper atoms together. Thiosemicarbazone HL and the complexes manifest antibacterial and antifungal activities. The studied substances are more active towards Gram-negative bacteria than towards Gram-positive bacteria and fungi. Complex 1 is the most active one towards Gram-positive bacteria and C. albicans, while the introduction of 1,10-phenanthroline into the inner sphere enhances the activity towards Gram-negative bacteria. Thiosemicarbazone and complexes 6 and 7 manifest antiradical activity that exceeds the activity of Trolox. HL and complex 1 manifest antiproliferative activity towards HL-60 cancer cells which exceeds the activity of their analogs with 2-formyl-/2-acetylpyridine 4-allylthiosemicarbazone.