A Series of New Molybdenum(VI) Complexes with theONS Donor Thiosemicarbazone Ligands

cis-Dioxomolybdenum(VI) complexes of a new ONN chelating thiosemicarbazidato ligand; synthesis, characterization, crystal, molecular structures and antioxidant activities

5-Chloro-4-methyl-2-hydroxybenzophenone S-propyl-4-phenyl-thiosemicarbazone (H2L) and its cis-dioxomolybdenum(VI) complexes, in the general formula [MoO2(L)R-OH)] (R: methyl, 1; ethyl, 2; n-propyl, 3; n-butyl, 4; n-pentyl, 5), were synthesized and characterized by micro analysis, electronic, infrared and (1)H and (13)C NMR spectra. The crystal structures of complexes, 1 and 3, have been solved by direct methods (SIR92) and refined to the residual indexes R1=0.098 and R1=0.052 respectively. Complexes 1 and 3 are crystallized in the triclinic space group P-1 with Z=2. The crystal study of complex 1 showed the first example of intermolecular hydrogen bond for this type of molybdenum-thiosemicarbazone complexes. The hydrogen bond is between the hydroxyl proton of attached alcohol and an oxo oxygen (in MoO2(2+) unit) of another complex molecule, and its bond distance (1.767(1)Å) is shorter than from the σ-coordination bonds in complex 1. Antioxidant activities of the compounds were determined by using 1,1-diphenyl-2-picrylhydrazyl (DPPH) method. Ligand showed 23.61% DPPH radical scavenging activity at 250 mg/L concentration. Cupric Reducing Antioxidant Capacity (CUPRAC) was also evaluated and trolox-equivalent antioxidant capacity (TEAC) values were found for ligand, 1 and 3 as 0.51, 0.33 and 0.30 respectively.

Mononuclear dioxomolybdenum(VI) thiosemicarbazonato complexes: Synthesis, characterization, structural illustration, in vitro DNA binding, cleavage, and antitumor properties

Four dioxomolybdenum(VI) complexes were synthesized by reacting [MoO2(acac)2] with N-ethyl-2-(5-bromo-2-hydroxybenzylidene) hydrazinecarbothioamide (1), N-ethyl-2-(5-allyl-3-methoxy-2-hydroxybenzylidene) hydrazinecarbothioamide (2), N-methyl-2-(3-tert-butyl-2-hydroxybenzylidene) hydrazinecarbothioamide (3), and N-ethyl-2-(3-methyl-2-hydroxybenzylidene) hydrazinecarbothioamide (4). The molecular structures of 1, 2, and all the synthesized complexes were determined using single crystal X-ray crystallography. The binding properties of the ligand and complexes with calf thymus DNA (CT-DNA) were investigated via UV, fluorescence titrations, and viscosity measurement. Gel electrophoresis revealed that all the complexes cleave pBR 322 plasmid DNA. The cytotoxicity of the complexes were studied against the HCT 116 human colorectal cell line. All the complexes exhibited more pronounced activity than the standard reference drug 5-fluorouracil (IC50 7.3μM). These studies show that dioxomolybdenum(VI) complexes could be potentially useful in chemotherapy.

Synthesis, Characterization, and Biological Studies of Binuclear Copper(II) Complexes of (2E)-2-(2-Hydroxy-3-Methoxybenzylidene)-4N-Substituted Hydrazinecarbothioamides

Four novel binuclear copper(II) complexes [1–4] of (2E)-2-(2-hydroxy-3-methoxybenzylidene)-4N-substituted hydrazinecarbothioamides, (OH)(OCH3)C6H4CH=NNHC(S)NHR, where R = H (L1), Me (L2), Et (L3), or Ph (L4), have been synthesized and characterized. The FT-IR spectral data suggested the attachment of copper(II) ion to ligand moiety through the azomethine nitrogen, thioketonic sulphur, and phenolic-O. The spectroscopic characterization indicates the dissociation of dimeric complex into mononuclear [Cu(L)Cl] units in polar solvents like DMSO, where L is monoanionic thiosemicarbazone. The DNA binding properties of the complexes with calf thymus (CT) DNA were studied by spectroscopic titration. The complexes show binding affinity to CT DNA with binding constant (Kb) values in the order of 106 M−1. The ligands and their metal complexes were tested for antibacterial and antifungal activities by agar disc diffusion method. Except for complex 4, all complexes showed considerable activity almost equal to the activity of ciprofloxacin. These complexes did not show any effect on Gram-negative bacteria, whereas they showed moderate activity for Gram-positive strains.

[N'-(3-Eth-oxy-2-oxidobenzyl-idene)-4-hy-droxy-3-meth-oxy-benzohydrazidato](methanol)dioxidomolybdenum(VI)

In the title dioxidomolybdenum(VI) complex, [Mo(C₁₇H₁₆N₂O₅)O₂(CH₃OH)], the Mo^VI atom is coordinated by the phenolate O, imine N and enolic O atoms of the tridentate hydrazone ligand, one methanol O atom, and two oxide O atoms, forming a distorted octa­hedral coordination geometry. The oxide O atoms adopt a cis conformation: one is trans to the methanol O atom and the other is trans to the ligand N atom. The dihedral angle between the two benzene rings in the hydrazone ligand is 4.0 (3)°. In the crystal, mol­ecules are linked by O—H⋯N and O—H⋯O hydrogen bonds.

Transition metal complexes with thiosemicarbazide-based ligands. Part 57: Synthesis, spectral and structural characterization of dioxovanadium(V) and dioxomolybdenum(VI) complexes with pyridoxal s-methylisothiosemicarbazone

This work is concerned with the synthesis of neutral dioxovanadium(V) and dioxomolybdenum(VI) complexes with tridentate ONN pyridoxal S-methylisothiosemicarbazone (PLITSC) of the respective formulas [VO2(PLITSC-H)]?2H2O and [MoO2(PLITSC-2H)]. Structural X-ray analysis of the vanadium complex showed that it has an almost ideal square-pyramidal structure, while the molybdenum complex is supposed to have a polymeric octahedral structure. In addition to elemental analysis, both complexes were characterized by conductometric and magnetometric measurements, as well as by IR, UV-vis, 1H- and 13CNMR spectra.