Oxovanadium(IV) complexes of bioinorganic and medicinal relevance: Synthesis, characterization and 3D molecular modeling of some oxovanadium(IV) complexes involving O, N-donor environment of salicylaldehyde-based sulfa drug Schiff bases

Bioactive Co(II), Ni(II), and Cu(II) Complexes Containing a Tridentate Sulfathiazole-Based (ONN) Schiff Base

New Co(II), Ni(II), and Cu(II) complexes were synthesized with the Schiff base ligand obtained by the condensation of sulfathiazole with salicylaldehyde. Their characterization was performed by elemental analysis, molar conductance, spectroscopic techniques (IR, diffuse reflectance and UV–Vis–NIR), magnetic moments, thermal analysis, and calorimetry (thermogravimetry/derivative thermogravimetry/differential scanning calorimetry), while their morphological and crystal systems were explained on the basis of powder X-ray diffraction results. The IR data indicated that the Schiff base ligand is tridentate coordinated to the metallic ion with two N atoms from azomethine group and thiazole ring and one O atom from phenolic group. The composition of the complexes was found to be of the [ML₂]∙nH₂O (M = Co, n = 1.5 (1); M = Ni, n = 1 (2); M = Cu, n = 4.5 (3)) type, having an octahedral geometry for the Co(II) and Ni(II) complexes and a tetragonally distorted octahedral geometry for the Cu(II) complex. The presence of lattice water molecules was confirmed by thermal analysis. XRD analysis evidenced the polycrystalline nature of the powders, with a monoclinic structure. The unit cell volume of the complexes was found to increase in the order of (2) < (1) < (3). SEM evidenced hard agglomerates with micrometric-range sizes for all the investigated samples (ligand and complexes). EDS analysis showed that the N:S and N:M atomic ratios were close to the theoretical ones (1.5 and 6.0, respectively). The geometric and electronic structures of the Schiff base ligand 4-((2-hydroxybenzylidene) amino)-N-(thiazol-2-yl) benzenesulfonamide (HL) was computationally investigated by the density functional theory (DFT) method. The predictive molecular properties of the chemical reactivity of the HL and Cu(II) complex were determined by a DFT calculation. The Schiff base and its metal complexes were tested against some bacterial strains (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Bacillus subtilis). The results indicated that the antibacterial activity of all metal complexes is better than that of the Schiff base.

Synthesis and Characterization of Oxidovanadium(IV) Complexes of 2-((E)-(6-Fluorobenzo[d]thiazol-2-ylimino)methyl)-6-methoxyphenol and Their Antimicrobial, Antioxidant, and DNA-Binding Studies

Two novel oxidovanadium(IV) complexes with a new bidentate (O- and N-) imine-based ligand 2-((E)-(6-fluorobenzo[d]thiazol-2-ylimino)methyl)-6-methoxyphenol (HL) were synthesized under in situ experimental condition where VOSO₄ acts as a kinetic template in the ratio 2 : 1 (L : M) and mixed ligand complex using 1,10-phenanthroline (phen) in 1 : 1 : 1 (L : M : phen) ratio. The synthesized compounds were structurally characterized by microanalysis, magnetic susceptibility, FTIR, electronic spectra, TG/DTA, ESR, and molar conductance studies. Based on the spectral studies, the complexes have the general composition [VO(L)₂] (C ₁ ) and [VO(L)phen] (C ₂ ) in a square pyramid geometrical fashion. The synthesized compounds were primarily screened for their in vitro growth inhibiting activity against different strains of bacteria, namely, E. coli, B. subtilis, S. aureus, and P. aeruginosa by the disc diffusion method. Also, the antifungal activity was determined against C. albicans and A. niger by the Bateman poisoned technique. The in vitro antioxidant activity of all the compounds was determined by DPPH free radical-scavenging assay. Intercalative mode of DNA-binding properties of the oxidovanadium(IV) complexes with calf-thymus DNA (CT-DNA) was investigated using UV, fluorescence spectra, and viscosity measurements.