Cezar Spinu

New biologically active mixed-ligand Co(II) and Ni(II) complexes of enrofloxacin

New mixed-ligand Co(II) and Ni(II) complexes with enrofloxacin and 1,10-phenanthroline/8-hydroxyquinoline have been synthesized. The metal complexes have been characterized by elemental analyses, molar conductance, FT-IR, solid reflectance, magnetic moment, thermal analyses, X-ray powder diffraction (XRD) and SEM analysis. Conductance measurements indicate that all the complexes are non-electrolytes. Spectral IR data showed that the deprotonated enrofloxacin is bidentately bound to the metal ion through the pyridone oxygen and the carboxylated oxygen; 1,10-phenanthroline acts as neutral bidentate ligand coordinated through two nitrogen donor atoms, and the deprotonated 8-hydroxyquinoline is coordinated through nitrogen and oxygen donor atoms. The geometry of the complexes was elucidated with solid reflectance UV and magnetic moments. Thermal analysis recorded that TG/DTG/DSC experiments revealed the thermal stability of metal complexes and confirmed their compositions suggested by the analytical data. In addition to experimental data, a molecular modelling study has been performed to establish the optimized geometries of metal complexes. The XRD analysis of powders evidences the nanocrystalline nature of all complexes. The results are in agreement with molecular modelling data. SEM images revealed highly agglomerated particles with irregular shape with sizes in the micrometre range. The ligand and their metal complexes were screened for their antimicrobial activity against Escherichia coli 25922, Staphylococcus aureus 25923, Pseudomonas aeruginosa 27853 and Candida albicans 10231. The metal complexes were also investigated for their cytotoxicity using an in vitro assay.

Catalytic Activity of Thallium on Electrochemical Degradation of Metronidazole from Aqueous Solutions

The platinum/thallium electrode was prepared by thallium electrodeposition on platinum substrate in order to use it for the increase of the electrochemical degradation rate of some drugs, such as, in our study, metronidazole (MNZ). The platinum/thallium electrode was characterized by chronoamperometry, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. 2D progressive nucleation mechanism of thallium layer development was found by chronoamperometry. The value of charge transfer resistance of 537.2 Ω cm2 and the double-layer capacitance value of 2.9 mF cm−2 were deduced by EIS. The scanning electron microscopy showed a relatively fine-grained structure and the uniform distribution of the thallium granules. The electrochemical degradation of metronidazole has been performed using galvanostatic technique associated with UV-Vis spectrophotometry. The degradation degree of metronidazole reached a higher level on platinum/thallium electrode than that on platinum plate, indicating its improved performance and electrocatalytic activity of thallium coating. Moreover, the electrochemical degradation mechanism of this drug was proposed, the best way to fit the experimental data being the kinetics model of the first-order reactions.