Kinetics and mechanism of oxidation of carbenicillin by diperiodatocuprate [DPC-III] in aqueous alkaline medium were studied spectrophotometrically at 298 K and an ionic strength of 0.10 mol·dm−3. The reaction between DPC (III) and carbenicillin in the alkaline medium showed (CRBC : DPC-III) 1 : 4 stoichiometry. The reaction products were identified by the CHNS test, FT-IR, and LC-MS spectral reports. The reaction was of pseudo-first order with respect to DPC (III) and fractional order with respect to carbenicillin as well as alkali but retarding effect with respect to periodate. Monoperiodatocuprate (MPC-III) was found to be the main active species in the alkaline medium in the form of [Cu (H2IO6) (H2O)2]. Activation and thermodynamic parameters with respect to uncatalyzed rate constants (ku) and slow step rate constant (k) as well as equilibrium constants were determined. The plausible mechanism consistent with experimental results was proposed and discussed in detail.

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The two new novel heteroleptic complexes of the type [M(II)L1.L2] (M= Zr(II) & Pd(II), L1= oxytetracycline (Otc), and L2=salicylaldehyde (Sal)) have been synthesized and analyzed by physical measurements such as CHN, pH, and conductivity. The conductivity data revealed the electrolytic nature of Pd(II)Otc/Sal and the non-electrolytic nature of the Zr(II)Otc/Sal metal complex of mixed ligand. The structural characterizations of the metal complex were approved by spectroscopic analysis methods, such as IR, 1H & 13C-NMR, UV/ Visible, and ESI-MS studies. Thermal analysis (TGA/DTA) determines the thermal and kinetic stabilities of the metal complexes using a popular Coats-Redfern equation through which the activation parameters can be calculated easily. SEM can determine the surface morphology of metal complexes. The selected bond lengths, bond angles, final optimized energy, and geometry of complexes were obtained by running an optimization task in the 3D molecular modeling software program via Chem 3D Pro. 12.0.2. The final geometrical energy was found to be 921.7712 for Zr(II)Otc/Sal and 914.6006 Kcal/mol for Pd(II)Otc/Sal complexes. Based on the above study, Zr(II)Otc/Sal complex has tetrahedral geometry and the Pd(II)Otc/Sal complex has square planar geometry. The complexes were tested in vitro for antibacterial susceptibility study against various strains of clinical pathogenic bacteria such as Staphylococcus aureus (Gram-positive), Proteus mirabilis, and Escherichia coli (Gram-negative). For the antibacterial study, the Kirby-Bauer paper disc diffusion technique is applied by using 50, 25, and 12.5 μg/μL concentrations of the metal complex. Good antibacterial sensitivity was found against all tested pathogens in all synthesized complexes.

Diperiodatocuprate [DPC (III)] was selected to predict the kinetic studies for carbenicillin (CRBC) oxidation in the basic media. The investigation was completed in the presence of CoCl3 as a catalyst by using a UV/Visible spectrophotometer at 298K temperature and 0.01 mol-dm-3 ionic strength confirming a 1:4 stoichiometry between CRBC and DPC (III). Both spectral and elemental analysis was used to identify the final products. Monoperiodatocuperate [MPC (III)] was found to be the primary active species of DPC (III). Pseudo-first order reaction was declared for DPC (III), while fractional order reactions were noticed in the case of CRBC (substrate), Co (III) catalyst as well as KOH (alkali). However, the reaction was determined to be in negative fractional order for periodate. Spectral evidence, determination of various rate constants, and both activation, as well as thermodynamic parameters, were used to predict plausible mechanisms.