Electrocarboxylation of chloroacetonitrile mediated by electrogenerated cobalt(I) phenanthroline

The electrocarboxylation of chloroacetonitrilemediated by [Co(II)(phen)3]2+ has been investigated. Cyclic voltammetry studies of [Co(II)(phen)3]2+ have shown that [Co(I)(phen)3]+, an 18 electron complex, activates chloroacetonitrile by an oxidative addition through the loss of a phenanthroline ligand to give [RCo(III)(phen)2Cl]+. The unstable one-electron-reduced complex underwent Co–C bond cleavage. In carbon dioxide saturated solution, CO2 insertion proceeds after reduction of the alkylcobalt complex. A catalytic current is observed which corresponds to the electrocarboxylation of chloroacetonitrile into cyanoacetic acid. Electrolyses confirmed the process and gave faradic yield of 62% in cyanoacetic acid at potentials that are about 0.3 V less cathodic than the one required for Ni(salen)

Electrocarboxylation of chloroacetonitrile by a Cobalt(I) complex of terpyridine

The electrocarboxylation of chloroacetonitrile (NC–CH2–ClRCl) mediated by [CoIIL2]2+ (L = terpyridine) was investigated by cyclic voltammetry. Electrochemical studies under argon atmosphere showed that the monoelectronic reduction of [CoIIL2]2+ yielded a Cobalt(I) complex which after the loss of a terpyridine ligand reacted with chloroacetonitrile. The oxidative addition of chloroacetonitrile on [CoIL]+ gave an alkylCobalt(III) complex [R–CoIIIL]2+ which was reduced into an alkylCobalt(II) complex, highly unstable and decomposed into an alkyl anion and a Cobalt(II) complex. Under carbon dioxide atmosphere, Cobalt(I) complex was shown to be unreactive towards CO2 but CO2 insertion was observed in the alkylCobalt(III) complex [R–CoIIIL] 2+ giving probably a CO2 adduct [R–CoIIIL(CO2)]2+. This adduct presented a strong adsorption at the carbon electrode and was reduced at potential less cathodic than the one of alkylCobalt(III) complex. After reduction, the carboxylate RCO2− (NC–CH2–CO2−) was released and a catalytic bielectronic carboxylation of chloroacetonitrile took place. Controlled potential electrolyses confirmed the catalytic process and gave for cyanoacetic acid faradic yields up to 60% under low overpotential conditions

Electrochemical study in both classical cell and microreactors of flavin adenine dinucleotide as a redox mediator for NADH regeneration

The electrochemical reduction of flavinadeninedinucleotide (FAD) is studied in a classical electrochemical cell as well as in two types of microreactors: the first one is a one-channel reactor and the other one, a multichannel filter-press reactor. The ultimate goal is to use the reduced form of flavin (FADH2), in the presence of formate dehydrogenase (FDH), in order to continuously regenerate the reduced form of nicotinamide adeninedinucleotide (NADH) for chiral syntheses. Various voltammetric and adsorption measurements were carried out for a better understanding of the redox behavior of the FAD as well as its adsorption on gold. Diffusivity and kinetic electrochemical parameters of FAD were determined

Unexpected effect of copper ions on electrochemical impedance behaviour of self-assembled alkylaminethiol monolayer

Effect of copper ions on the electrochemical behaviour of an alkylaminethiol monolayer has been studied by electrochemical impedance spectrosocpy. RAMAN experiment shows the effective adsorption of receptor onto the gold surfaces. The study of Nyquist plot shows that the gold/monolayer/electrolyte interface can be described by a serial combination of two R, CPE electrical circuits. In the presence of increasing amounts of copper, the Nyquist plots at low frequencies were modified showing an increase of the resistance of the second R, CPE electrical circuit. Moreover, this increase of resistance varies linearly with the amounts of copper ions added in solution from 10−8 mol·L−1 to 10−5 mol·L−1

Programmable multimetallic linear nanoassemblies of ruthenium–DNA conjugates

A new ruthenium–DNA conjugates family was synthesized, made up of a ruthenium complex bound to one or two identical DNA strands of 14–58 nucleotides. The formation of controlled linear nanoassemblies containing one to seven ruthenium complexes is described

Electrochemical impedance spectroscopy to study physiological changes affecting the red blood cell after invasion by malaria parasites

The malaria parasite, Plasmodium falciparum, invades human erythrocytes and induces dramatic changes in the host cell. The idea of this work was to use RBC modified electrode to perform electrochemical impedance spectroscopy (EIS) with the aim of monitoring physiological changes affecting the erythrocyte after invasion by the malaria parasite. Impedance cell-based devices are potentially useful to give insight into cellular behavior and to detect morphological changes. The modelling of impedance plots (Nyquist diagram) in equivalent circuit taking into account the presence of the cellular layer, allowed us pointing out specific events associated with the development of the parasite such as (i) strong changes in the host cell cytoplasm illustrated by changes in the film capacity, (ii) perturbation of the ionic composition of the host cell illustrated by changes in the film resistance, (iii) releasing of reducer (lactic acid or heme) and an enhanced oxygen consumption characterized by changes in the charge transfer resistance and in the Warburg coefficient characteristic of the redox species diffusion. These results show that the RBC-based device may help to analyze strategic events in the malaria parasite development constituting a new tool in antimalarial research