Théodore Tzedakis

Bicyclic peroxides in the G factors series: synthesis and electrochemical studies

Abstract Endoperoxides belonging to the family of G factors have been synthesised under Mannich type conditions. The structure of different diastereoisomers has been established on the basis of NMR experiments. Their cathodic peak potentials have been determined by thin-layer electrochemistry under potentiostatic conditions, and compared to that of artemisinin.

Study of the mechanism of the electrochemical deposition of silver from an aqueous silver iodide suspension

The present work examines the reduction of solid silver iodide on a silver electrode and proposes a mechanism for this process. Voltammetric and coulometric studies for the steady and transient states showed adsorption of silver iodide at the electrode depending on its concentration; this adsorption is in accordance with the Langmuir isotherm for low concentrations and with multi-layer models (such as the BET isotherm) for higher concentrations. Reduction of silver iodide at the silver electrode can take place through several processes such as direct reduction of solid particles, or reduction of the adsorbed silver iodide and involves the formation of a dendritic silver deposit not adhering to the electrode and free iodide in solution. Silver is then recovered easily by filtration of the initial suspension.

Electrochemical study of binuclear manganese complexes as catalysts in Kraft pulp bleaching

Abstract The redox behaviour, stability and catalytic properties of various binuclear manganese–ligand complexes was examined by electrochemical thin layer and potential measurements. Some of the complexes studied were irreversibly degraded by oxidation at high potentials, while others were dissociated in aqueous media to give the monomeric form. Otherwise, most of these complexes occur in acid–base equilibria, namely through protonation of the ligand amino functions. The manganese–Tris-(2-methyl pyridyl) amine complex is stable without dissociation at pH 3–5 and temperatures of 15–80°C. The results show that after several successive scans in the 0–1 V range the complex can be oxidised or reduced without irreversible degradation; it can be used in catalytic amounts (0.1 g of complex per g Kraft pulp) for lignin oxidation by hydrogen peroxide.

Electrochemical characterization of the {(TPA)Mn(III)O2Mn(IV)(TPA)}2(SO4)3 complex

Abstract Thin-layer electrochemistry and steady-state current-potential curves were used to study the electrochemical behavior of the {(TPA)Mn(III)O2Mn(IV)(TPA)}2(SO4)3 complex in an aqueous medium and forecast its role in a catalytic reaction using the usual oxidants. By studying the concentration and pH effects it is possible to assess the complexs stability domain, on the one hand, and to characterize the oxidation state of the two manganese atoms and construct a potential-pH diagram including the various equilibria between the manganese species on the other.

Differential pulse polarography for monitoring cell cultures

The differential pulse polarography has been used on samples taken from the medium during the culture of chinese hamster ovary cells with a view to producing the active principle of an anti-cancer drug.