Hydrazone complexes of Cu(II), Co(II), Zn(II), Ni(II) and Pt(II) with N-isonicotinoyl-N′-(3-metoxy-2 hydroxybenzaldehyde)-hydrazone (HL) were synthesized and characterized by different physico-chemical techniques including elemental and thermal analysis, magnetic susceptibility measurements, molar electric conductivity, as well as IR (infrared), ¹H-NMR and ¹³C-NMR (hydrogen and carbon nuclear magnetic resonance, UV-Vis (ultraviolet-visible), FAB (fast atom bombardment), EPR (electron paramagnetic resonance), and mass spectroscopies. The crystal structure of ligand was determined by single crystal X-ray diffraction studies. Spectral data showed that hydrazone behaves as an ONO tridentate ligand through the azomethine nitrogen, phenolate and keto oxygen atoms. For the copper(II) complexes, metal–ligand bonding parameters were evaluated from the EPR spectra. These parameters indicate the presence of in-plane π bonding. In addition, the f values of complexes 1–4 indicate small distortion from planarity. The effect of these complexes on proliferation of human breast cancer (MCF-7 and SKBR-3), human melanoma (A375), lung adenocarcinoma cells (NCI-H1573) and their antibacterial activity against Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus and Candida albicans strains were studied and compared with those of free ligand. The ligand and complexes 1–3 showed significant antimicrobial activity against the Gram-positive bacteria Staphylococcus aureus and Candida albicans in comparison to the control drugs. The complexes 2–4 could be potential antitumor agents, leading to a significant improvement of the cytotoxic activity when compared with HL.

A novel Schiff base, ethyl 4-[(E)-(2-hydroxy-4-methoxyphenyl)methylene-amino]benzoate (HL), was prepared and structurally characterized on the basis of elemental analyses, ¹H NMR, ¹³C NMR, UV-Vis and IR spectral data. Six new copper(II) complexes, [Cu(L)(NO₃)(H₂O)₂] (1), [Cu(L)₂] (2), [Cu(L)(OAc)] (3), [Cu₂ (L)₂Cl₂(H₂O)₄] (4), [Cu(L)(ClO₄)(H₂O)] (5) and [Cu₂(L₂S)(ClO₄)(H₂O)]ClO₄·H₂O (6) have been synthesized. The characterization of the newly formed compounds was done by IR, UV-Vis, EPR, FAB mass spectroscopy, elemental and thermal analysis, magnetic susceptibility measurements and molar electric conductivity. The crystal structures of Schiff base and the complex [Cu₂(L₂S)(ClO₄)(H₂O)]ClO₄·H₂O (6) have been determined by single crystal X-ray diffraction studies. Both copper atoms display a distorted octahedral coordination type [O₄NS]. This coordination is ensured by three phenol oxygen, two of which being related to the µ-oxo-bridge, the nitrogen atoms of the azomethine group and the sulfur atoms that come from the polydentate ligand. The in vitro antimicrobial activity against Escherichia coli ATCC 25922, Salmonella enteritidis, Staphylococcus aureus ATCC 25923, Enterococcus and Candida albicans strains was studied and compared with that of free ligand. The complexes 1, 2, 5 showed a better antimicrobial activity than the Schiff base against the tested microorganisms.

The chelating behavior of the thiosemicarbazone derivatives of 2-hydroxy-8-R-tricyclo[7.3.1.0.^2,7]tridecane-13-one (where R = H, CH₃, C₆H₅) towards Co(II), Ni(II) and Cu(II) has been investigated by elemental analysis, molar conductivity measurements, UV-VIS, IR, ESR spectroscopy and thermal studies. It was deduced from the experiments performed that the ligands coordinate to metal ions in different ways – neutral bidentate or mononegative bidentate – depending on the nature of R. Also, if metal acetates are used instead of metal chlorides, the ligands coordinate in a mononegative bidentate fashion, regardless of the nature of R or the thiosemicarbazone type ligand. The antimicrobial activity of the ligands and of the complexes towards samples of Acinetobacter boumanii, Klebsiella pneumoniae, Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa was determined.

The present paper describes the synthesis, characterization and in vitro biological evaluation screening of different classes (ammoniacates, dioximates, carboxylates, semi- and thiosemicarbazidates) of Co(II), Co(III), Cu(II), Ni(II), Mn(II), Zn(II) and Fe(III) complexes. Schiff bases were obtained from the reaction of some salicyl aldehydes with, respectively, furoylhydrazine, benzoylhydrazine, semicarbazide, thiosemicarbazide and S-methylthiosemicarbazide to give tridentate ligands containing ONO, ONS or ONN as donor atoms. The synthetic metal complexes are of various geometrical and electronic structures, thermodynamic and thermal stabilities, and magnetic and conductance properties. All complexes, except those of Cu, are octahedral. Some Cu, Co and Mn compounds have a dimeric or a polymeric structure. The composition and structure of complexes were analysed by elemental analysis, IR and ¹H NMR and ¹³C NMR spectroscopies, and magnetochemical, thermoanalytical and molar conductance measurements. All ligands and metal complexes were tested as inhibitors of human leukemia (HL-60) cells growth, and the most potent, the Cu(II) complexes, have been also tested for their in vitro antibacterial and antifungal activities. Structure-activity relationships were carried out.

New Cu(II), Pd(II) and Pt(II) complexes, (Cu(L)(H₂O)₂(OAc)) (1), (Cu(HL)(H₂O)₂(SO₄)) (2), (Cu(L)(H₂O)₂(NO₃)) (3), (Cu(L)(H₂O)₂(ClO₄)) (4), (Cu(L)₂(H₂O)₂) (5), (Pd(L)(OAc))H₂O (6), and (Pt(L)₂) (7) were synthesized from 8-ethyl-2-hydroxytricyclo(7.3.1.0^2,7)tridecan-13-one thiosemicarbazone (HL). The ligand and its metal complexes were characterized by IR, ¹H-NMR, ¹³C-NMR, UV-Vis, FAB, EPR, mass spectroscopy, elemental and thermal analysis, magnetic susceptibility measurements and molar electric conductivity. The free ligand and the metal complexes have been tested for their antimicrobial activity against E. coli, S. enteritidis, S. aureus, E. faecalis, C. albicans and cytotoxicity against the NCI-H1573 lung adenocarcinoma, SKBR-3 human breast, MCF-7 human breast, A375 human melanoma and HL-60 human promyelocytic leukemia cell lines. Copper complex 2 exhibited the best antiproliferative activities against MCF-7 human breast cancer cells. A significant inhibition of malignant HL-60 cell growth was observed for copper complex 2, palladium complex 6 and platinum complex 7, with IC₅₀ values of 1.6 µM, 6.5 µM and 6.4 µM, respectively.

Thiosemicarbazone-based compounds have attracted significant attention in recent years due to their potential as inhibitors of cancer cell proliferation. They not only exhibit strong antiproliferative effects but also possess antioxidant properties that are crucial in combating oxidative stress linked to cancer progression. This review highlights specific compounds that not only exhibit significantly higher antiproliferative activities but also demonstrate lower toxicity compared to traditional chemotherapy agents. This is important because it suggests that these compounds could provide better treatment options while reducing the side effects often associated with chemotherapy. A detailed analysis of the structure–activity relationships (SARs) reveals that the unique structural features of these compounds play a crucial role in their enhanced effectiveness. Understanding which molecular characteristics contribute to improved activity will be key for future compound design. The findings from this study emphasize the need for further exploration and development of these novel agents. By investigating their biological mechanisms and optimizing their structures, researchers can improve cancer treatment strategies, providing safer and more effective options for patients. Despite substantial previous research on thiosemicarbazones and isothiosemicarbazones, the field still holds many unknowns and opportunities for discovery. Studying coordination chemistry with 3d metal ions and strategically modifying their inner structures may lead to new compounds with promising biological activities and selectivity. Overall, exploring thiosemicarbazones and isothiosemicarbazones as innovative pharmacological agents against cancer could unlock their full potential, significantly enhancing cancer treatment protocols and improving patient survival rates.