Transition metal complexes with the thiosemicarbazide-based ligands—XXIII. Synthesis, physicochemical properties and voltammetric characterization of iron(III) complexes with terdentate and quadridentate thiosemicarbazide derivatives

New thiosemicarbazone-based Zinc(II) complexes. In vitro cytotoxicity competing with cisplatin on malignant melanoma A375 cells and its relation to neuraminidase inhibition

New thiosemicarbazone-based zinc(II) complexes were synthesized to study their cytotoxicity on A375 malignant melanoma cells. The complexes containing salicylidene (Zn1a), 3-methoxy-salicylidene (Zn1b) or 4-methoxy-salicylidene (Zn1c) moiety were characterized by analytical and spectroscopic methods. Anticancer potential of the complexes was determined by MTT test and HUVEC endothelial cells line was used to comprehend the effect on normal cells. Zn1b with an IC₅₀ of 13 μM was found to be highly cytotoxic against A375 cancer cells, more effective than cisplatin (IC₅₀: 37 μM). Zn1a and Zn1c did not have a negative effect on cell viability in the normal cells and gave the impression that they are more advantageous than cisplatin in this respect. Further, the ability of Zn1a-c to inhibit neuraminidase enzyme and its role in cytotoxicity was discussed. The test revealed that the Zn1b with 3-methoxy substituent exhibited higher inhibition activity against the neuraminidase than the Zn1a and Zn1c as analogical to the cytotoxicity results. In neuraminidase inhibition, IC₅₀ values of Zn1b and Zn1c were 14 and 66 μM, respectively. These concentrations were very close to the cytotoxicity concentrations for Zn1b and Zn1c. The findings may indicate the role of neuraminidase enzyme inhibition in cell death for Zn1b and Zn1c.

Preparation, characterization and antibacterial effect of 2-methoxy-6-(5-H/Me/Cl/No2-1H-benzimidazol-2-yl)phenols and some transition metal complexes

2-Methoxy-6-(5-H/methyl/chloro/nitro-1H-benzimidazol-2-yl)phenols (HLx; x = 1-4, respectively) ligands and HL1 complexes with Fe(NO3)3, Cu(NO3)2, AgNO3 and Zn(NO3)2 were synthesized and characterized. The structures of the compounds were confirmed based on elemental analysis, molar conductivity, magnetic moment, FT-IR, 1H- and 13C-NMR. The antibacterial activity and minimum inhibitory concentration (MIC) of the free ligands, their hydrochloride salts and the complexes were evaluated using the disk diffusion method in dimethyl sulfoxide (DMSO) and the dilution method, respectively, against 9 bacteria. HL1 and HL3, as well as the Cu(II) and Zn(II) complexes, showed antibacterial activity against Gram-positive bacteria.

Structural, Spectral, Electric-Field-Induced Second Harmonic, and Theoretical Study of Ni(II), Cu(II), Zn(II), and VO(II) Complexes with [N2O2] Unsymmetrical Schiff Bases of S-Methylisothiosemicarbazide Derivatives

New unsymmetrical [N2O2] tetradentate Schiff base complexes of Ni(II), Cu(II), Zn(II), and VO(II) were synthesized by template condensation of the tetradentate precursor 1-phenylbutane-1,3-dione mono-S-methylisothiosemicarbazone with o-hydroxybenzaldehyde or its 5-phenylazo derivative. They were characterized by elemental analysis, IR, UV-vis, electron spin resonance, and NMR spectroscopy, mass spectrometry, and magnetic measurements. The crystal structures of five of them have been determined by X-ray diffraction using, in some cases, synchrotron radiation. These compounds are characterized by a large thermal stability; their decomposition temperatures range from 240 up to 310 degrees C. Complexes with the phenylazo substituent were found to possess a large second-order nonlinear optical (NLO) response, as determined both by measurements of solution-phase direct current electric-field-induced second harmonic generation and by theoretical time-dependent density functional theory (TDDFT) calculations. The molecular hyperpolarizability was found to decrease in the order Zn(II) > Cu(II) > Ni(II) approximately VO(II). The active role of the metal in determining the NLO properties of the complexes was shown through an analysis of their UV-vis spectra, which revealed the presence of metal-to-ligand (in closed-shell complexes) and ligand-to-metal (in open-shell complexes) charge-transfer bands together with intra-ligand charge-transfer transitions. Assignment of the bands was based on the analysis of the TDDFT computed spectra.

Antiproliferative activities of iron and platinum conjugates of salicylaldehyde semi-/thiosemicarbazones against C6 glioma cells

The identification of novel therapeutic agents for the management of malignant gliomas represents an area of active research. Here, we show that among the iron and platinum complexes of 2-hydroxybenzaldehyde semi-/thiosemicarbazones the latter inhibits the growth of C6 glioma cells in vitro with an IC50 value of 45 microM. Structural characterization reveals iron complexes to be octahedral having intermediate S = 3/2 spin states while platinum complexes are found to be square planar moieties. Our findings suggest that the platinum compounds of 2-hydroxybenzaldehyde thiosemicarbazone are potential candidates for the treatment of malignant gliomas.