Synthesis, characterization and structural study of new vanadium complexes with phenolic oxime ligands

Preparation of Cu(II), Ni(II), Ti(IV), VO(IV), and Zn(II) Metal Complexes Derived from Novel vic-Dioxime and Investigation of Their Antioxidant and Antibacterial Activities

In this work, novel vic-dioxime ligand (LH₂ ) containing bound to the N₄ -oxime core moiety and its complexes with Cu(II), Ni(II), Ti(IV), VO(IV), and Zn(II) salts have been studied. The structure of the ligand and its complexes were successfully synthesized and characterized using NMR (¹ H and ¹³ C), LC/MS/MS spectrometer, FT-IR and UV/VIS spectroscopy, melting point, and magnetic susceptibility measurements. Vic-dioxime ligand (LH₂ ) (1) and its metal complexes ([Cu(LH)₂ ] (2), [Ni(LH)₂ ] (3), [Ti(LH)₂ ]Cl₂ (4), [VO(LH)₂ ] (5), and [Zn(LH)₂ ] (6), respectively) were tested for them in-vitro antibacterial and antioxidant activities. According to the metal chelating results of the study, it was determined that compounds (1), (2), (3), and (6) showed very good activity, and especially compound (2), had a stronger metal chelating capacity due to ligand dissociation from the synthesized metal complexes, which then would chelate Fe(II) in the experimental setting. When microorganisms were evaluated in terms of the % viability effect, it was observed that all compounds had activity against C. Albicans and S. Cerevisiae at rates similar to antibiotics.

Oxovanadium(IV) and Nickel(II) complexes obtained from 2,2'-dihydroxybenzophenone-S-methyl-thiosemicarbazone: Synthesis, characterization, electrochemistry, and antioxidant capability

2,2'-Dihydroxybenzophenone-S-methyl-thiosemicarbazone and 3-methoxy-salicylaldehyde were reacted in the presence of oxovanadium(IV) or nickel(II) ions to yield the N2O2-type-chelate complex. The synthesized complexes were characterized by employing elemental analysis, electronic and infrared spectra, 1H NMR spectra, magnetic measurements, and thermogravimetric analyses. The expected structures of oxovanadium(IV) and nickel(II) complexes were confirmed by using the single-crystal X-ray diffraction method. The presence of π-π stacked dimeric structures provided stronger crystalline formations. The optimized geometries and vibrational frequencies of the compounds were obtained using the DFT/ωB97XD method with the 6-31G (d,p) basis set and compared with the experimental data. The electrochemical characterization of the oxovanadium(IV) and nickel(II) complexes were carried out by using the cyclic voltammetry (CV) method. The oxovanadium(IV) complex gives a ligand-centered oxidation and a metal-centered one electron reduction and oxidation peaks corresponding to the VIV/IIIO and VIV/VO, respectively. The nickel(II) complex gives a ligand-centered oxidation and metal-centered (NiII/I) reduction peaks in a dimethyl sulfoxide (DMSO) solution. The redox potentials were calculated in terms of Gibbs free energy change of the redox reaction at the theory level of M06-L/LANL2DZ/PCM. In addition, the energy gap, HOMO and LUMO distributions were calculated. The total antioxidant capacities of the compounds were determined by using cupric reducing antioxidant capacity (CUPRAC) method, in which the oxovanadium(IV) complex was found to be powerful as an antioxidant agent.