Electrochemical and electrocatalytic studies of the N,N′-(1R,2R)-(–)-1,2-cyclohexylenebis(salicylideneiminato)cobalt(II) complex

The electrochemical properties and catalytic activity of a Co(II) complex with the optically active Schiff base derived from (1R,2R)-(–)-cyclohexanediamine and salicylaldehyde have been studied in non-aqueous solutions. When dissolved in deoxygenated non-aqueous solutions, the complex exhibits reversible redox properties for the Co(II)/Co(III) couple. Electrochemical reduction of oxygen and oxidation of cobalt(II) was observed on cyclic voltammograms of solutions containing both dioxygen and the Schiff base-cobalt(II) complex. An anodically formed film on a platinum electrode, studied by means of X-ray photoelectron spectroscopy, revealed the presence of the oxidized Co(III) species. Cyclic voltammetry of oxygenated solutions examined after a period of time indicates an electrochemical activity of coordinated superoxo/peroxo species in the 0.7–1.1 V potential range. In the presence of 4-methyl-1-cyclohexene the cyclic voltammetry curves reveal changes similar to those caused by the removal of oxygen. The GC-MS technique was used to identify some of the products formed by the catalytic oxidation of cyclohexene and 4-methyl-1-cyclohexene. Electronic Publication     

Cyclovoltammetric and spectroscopic characterization of optically active cobalt(II) and copper(II) complexes with the Schiff base derived from (N,N′)-(1R,2R)-(−)-cyclohexylenediamine and 2-hydroxyacetophenone

The Schiff base prepared by reacting (–)-(1R,2R)-1,2-cyclohexanediamine with 2-hydroxyacetophenone was used as a ligand for Co^II and Cu^II. The coordination compounds were studied by u.v.–vis. absorption and by circular dichroism (c.d.) spectroscopy in solution. The complexes are four-coordinated in a slightly distorted square planar symmetry. The distortion from planarity is a main factor influencing the chiral surroundings of the metal ion. The d–d and c.t. transitions are consistent with the observed distortion, which arises from intramolecular interactions between the methyl groups attached to the Schiff base imine carbon and hydrogen atoms of the cyclohexane ring. The electrochemical properties of the Co^II and Cu^II complexes were observed in MeCN but investigations revealed weaker oxygen activation than of Co^II analogue with salicylaldehyde. The Cu^II complex is reduced in H₂O to Cu^I which disproportionates to Cu^II and Cu⁰.     

Voltammetric and FT-IR studies of modified activated carbon systems with phenol, 4-chlorophenol or 1,4-benzoquinone adsorbed from aqueous electrolyte solutions

Cyclic voltammetric and spectral FT-IR studies of the influence of surface chemistry on the adsorption and electrochemical behaviour of powdered activated carbon electrodes (PACE) in the presence of phenol, 4-chlorophenol and 1,4-benzoquinone were carried out. The variety of surface chemical properties was achieved through modification of the carbon samples by heat treatment under vacuum and in an oxygen–ammonia atmosphere as well as by oxidation with conc. nitric acid. Adsorption processes were carried out from aqueous solutions (in air and an oxygen-free atmosphere) in the presence acidic, neutral or basic electrolytes. Some electrochemical parameters of electrode systems with adsorbed organics were estimated and correlated with the adsorption ability of carbon materials. The changes in FT-IR spectra of the carbons caused by adsorption and/or coupling organic molecules are presented and discussed.     

Cyclic voltammetric studies of heat treated and oxidized carbon fibres in organic and aqueous solutions

Summary Cyclic voltammetry was used to compare the electrochemical behaviour ofPAN-based carbon fibre electrodes in aqueous (differentpH), acetonitrile and methanol solutions. The sets of fibres used were produced at three temperatures and were oxidized with conc. HNO₃ or left nonmodified. The electrode reaction meachanisms probably occurring on the carbon fibre surfaces were analyzed.

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Untersuchung thermisch behandelter und oxydierter Kohlefasern mittels zyklischer Voltammetrie in organische und wässrigen Lösungen

Zusammenfassung Es wurde das elektrochemische Verhalten von Kohlefaserelektroden in wassrigen (verschiedenerpH-werl), acetonitrilischen und methanolischen Lösungen verglichen. Die Kohlefasern aufPAN(Polyacrylnitril)-Basis, die sich voneinander in der Temperatur der termischen Behandlung unterscheiden und nicht oder mit konzentrierter Salpetersäure oxidiert wurden, wurden mittels zyklischer Voltammetrie untersucht. Der wahrscheinliche Verlauf der Elektrodeprozesse auf den Kohlefasernoberflächen wurde analysiert.