Electrochemical reduction of nickel(II) dithiocarboxylates at the mercury electrode

1997 ◽  
Vol 75 (7) ◽  
pp. 1023-1029 ◽  
Author(s):  
A. Safavi ◽  
L. Fotouhi
Keyword(s):  
Electron Transfer ◽  
Electrochemical Techniques ◽  
Mercury Electrode ◽  
Electrode Reaction ◽  
Ece Mechanism ◽  
Reduction Mechanisms ◽  
Ec Mechanism ◽  
Controlled Potential ◽  
Electron Reduction ◽  
Derivatives Of

The reduction mechanisms of a series of nickel(II) dithiocarboxylate complexes have been investigated in dimethyl sulphoxide at the mercury electrode. Various electrochemical techniques, including polarography, cyclic voltammetry, chronoamperometry, and controlled potential coulometry, were employed. The reduction of the complexes of the acid derivatives of 2-aminocyclopentene-1-dithiocarboxylate (ACD) proceeds initially by an ECE mechanism (electron transfer – chemical reaction – electron transfer) followed by a one-electron irreversible process. The nature of the complete electrode reaction suggests a metal-centered reduction. The nickel complexes of the ester derivatives of ACD underwent a one-electron reduction that was subject to a follow-up catalytic reaction (EC′ mechanism) and the original complex is regenerated through this regeneration reaction. Keywords: reduction, nickel(II) dithiocarboxylate, mercury electrode.

Electrochemical reduction of the nickel(II) dithiocarbamates at the mercury electrode

1976 ◽  
Vol 29 (6) ◽  
pp. 1191 ◽  
Author(s):  
TH Randle ◽  
TJ Cardwell ◽  
RJ Magee
Keyword(s):  
Electron Transfer ◽  
Chemical Reaction ◽  
Mercury Electrode ◽  
Electrode Reaction ◽  
Reduction Mechanism ◽  
Ece Mechanism ◽  
Controlled Potential ◽  
Nickel Species ◽  
Electron Transfers ◽  
Potential Conditions

The reduction mechanism of a series of nickel(11) dithiocarbamates has been investigated in dimethyl sulphoxide at the mercury electrode. Under controlled-potential conditions, the reduction proceeds initially by an ECE mechanism (electron transfer-chemical reaction-electron transfer) with n = 1 for both electron transfers. The chemical reaction involves a dissociation to produce a nickel species more easily reduced than the nickel(11) dithiocarbamate. However, for some derivatives, rate constants for the chemical step show a time dependence, at electrolysis times above 5 s, consistent with an ECCE mechanism of the type where the product of the first chemical reaction reacts further to produce a nickel species more difficult to reduce than nickel(11) dithiocarbamate. Exhaustive reduction of nickel(11) diethyldithiocarbamate at the mercury-pool electrode gave non-integral n-values (2 > n > 1) consistent with the ECCE mechanism, and demonstrated that the product of the second chemical reaction is reoxidized to nickel(11) diethyldithiocarbamate by oxygen. The nature of the complete electrode reaction suggests a metal-centred reduction.

Electrochemical studies of Schiff base compounds derived from antipyrine nucleus in ethanolic buffer solutions

2000 ◽  
Vol 78 (9) ◽  
pp. 1170-1177 ◽  
Author(s):  
Ibrahim S El-Hallag ◽  
Gad B El-Hefnawy ◽  
Youssef I Moharram ◽  
Enass M Ghoneim
Keyword(s):  
Schiff Base ◽  
Electrochemical Behaviour ◽  
Electrochemical Techniques ◽  
Mercury Electrode ◽  
Electrode Reaction ◽  
Limiting Current ◽  
Electron Transfer Process ◽  
Buffer Solutions ◽  
Mechanistic Pathway ◽  
Electrochemical Parameters

The electrochemical behaviour of Schiff base compounds derived from an antipyrine nucleus was investigated in 30% (v/v) ethanolic buffer solutions (pH 3-11) using various electrochemical techniques at mercury electrode. The results showed that, the total limiting current of each of the studied compounds corresponds to 2-electron transfer process. The mechanistic pathway of the electrode reaction of the investigated compounds at mercury electrode, the effect of the medium, and the evaluation of the electrode reaction parameters were illustrated and discussed.Key words: Schiff base, antipyrine nucleus, electrode reaction, electrochemical parameters, cyclic voltammetry.

Electron-transfer biosensors

1987 ◽  
Vol 316 (1176) ◽  
pp. 95-106 ◽  
Keyword(s):  
Electron Transfer ◽  
Glucose Oxidase ◽  
Organometallic Compound ◽  
Electrode Reaction ◽  
Transfer Reactions ◽  
Ferrocene Derivatives ◽  
Electron Transfer Reactions ◽  
Redox Proteins ◽  
Copper Protein ◽  
Derivatives Of

The electrochemistry of redox proteins is now well established. Conditions exist which allow electron-transfer reactions of all simple proteins to proceed rapidly and reversibly at electrodes. Coupling of the electrode reaction to enzymes, for which the redox proteins act as cofactors, allows exploitation of this good electrochemistry. This is well illustrated by the enzyme-catalysed electrochemical oxidation of p -cresol to p -hydroxybenzaldehyde, which has been shown to proceed along with coupling to the electrode via the copper protein, azurin, or the organometallic compound ferroceneboronic acid. Ferrocene derivatives, in general, show a degree of versatility, coupling the electron-transfer reactions of many enzymes. Thus derivatives of the ferricinium ion act as excellent electron-transfer reagents from the enzyme glucose oxidase. The system is capable of detecting glucose in blood. Similar procedures, in conjunction with the appropriate enzyme, have yielded assays for, among others, H 2 O 2 and cholesterol.

Electrochemical investigation of reduction of mercury complexes of 2-aminocyclopentene-1-dithiocarboxylic acid and some of its derivatives at mercury electrodes

1996 ◽  
Vol 74 (1) ◽  
pp. 95-102 ◽  
Author(s):  
A. Safavi ◽  
M. B. Gholivand
Keyword(s):  
Electrochemical Techniques ◽  
Mercury Electrode ◽  
Elemental Mercury ◽  
Redox Processes ◽  
Electrochemical Investigation ◽  
Controlled Potential Electrolysis ◽  
Mercury Complexes ◽  
Controlled Potential ◽  
Mercury Electrodes ◽  
Complementary Study

Electrochemical techniques of polarography, cyclic voltammetry, and controlled potential electrolysis at mercury electrodes have permitted a detailed investigation of the reduction reactions associated with mercury 2-aminocyclopentene dithiocarboxylate complexes, Hg(ACD)2, in dimethyl sulphoxide (DMSO). As a complementary study, the electrochemistry of the ligands themselves was investigated in DMSO solutions and at mercury electrodes. The lability of mercury(II) complexes and their rapid interaction with elemental mercury strongly influence the nature of the redox processes observed at mercury electrodes. Reduction of Hg(ACD)2 at a mercury electrode occurs in an overall two-electron step as:[Formula: see text]although mercury(I) is implicated as an intermediate. Key words: reduction, electrochemical techniques, mercury complexes.

Polarography and coulometry of Rh(III) in a pyridine – pyridinium chloride electrolyte

1969 ◽  
Vol 47 (12) ◽  
pp. 2123-2135 ◽  
Author(s):  
Leslie E. Johnston ◽  
John A. Page
Keyword(s):  
Mercury Electrode ◽  
Normal Wave ◽  
Bulk Solution ◽  
Pyridinium Chloride ◽  
Chloride Electrolyte ◽  
Catalytic Wave ◽  
Controlled Potential Electrolysis ◽  
Dropping Mercury Electrode ◽  
Controlled Potential ◽  
Electron Reduction

The polarography and coulometry of Rh(III) has been studied in an aqueous pyridine–pyridinium chloride–sodium chloride electrolyte at pH 5.30 and ionic strength 0.30 M at 25.0 °C. Two distinct types of polarographic behavior were noted as the total Py concentration was varied between 0.05 and 0.45 M, a "normal" wave with E1/2 of −0.43 V vs. a standard calomel electrode, and a second catalytic wave which under some conditions masked the normal wave.For both types of behavior, controlled potential electrolysis gave a well-defined two electron reduction but there was a definite H+ consumption in the electrolyses. It is postulated that hydride species are involved in the reduction according to the scheme[Formula: see text]surface reaction at dropping mercury electrode[Formula: see text]slow, bulk solution in controlled potential electrolysis

scholarly journals Voltammetric studies of some azo compounds derived from 4-methyl-6,7-dihydroxy coumarin in microemulsion and aqueous media

2011 ◽  
Vol 7 (1) ◽  
pp. 1271-1279
Author(s):  
Omar A. Hazazi ◽  
Refat El-Sayed ◽  
El-Sayed. M. Mabrouk
Keyword(s):  
Reaction Pathway ◽  
Aqueous Media ◽  
Reduction Process ◽  
Electrode Reaction ◽  
Azo Compounds ◽  
Controlled Potential ◽  
Voltammetric Studies ◽  
Electron Reduction ◽  
Amine Compounds ◽  
Controlled Potential Coulometry

The cyclic voltammetric(CV) behavior of some azo compounds based on coumarin derivatives  was investigated in microemulsion systems and in aqueous solutions. The obtained results indicated that these compounds undergo an irreversible 4-electron reduction step leading to cleavage of the N=N center with the formation of amine compounds in all media. The effect of medium on the CV parameters was discussed. The total number of electrons involved in the reduction process was determined by controlled potential coulometry. Also, The effect of substituents on the electrode reaction pathway and the kinetic parameters of the electrode process were calculated and discussed. Based on the data obtained the electroreduction mechanism was suggested and discussed.

Electrochemical Reduction of 1-Halo-2-butenes in Dimethylformamide

1993 ◽  
Vol 58 (12) ◽  
pp. 2875-2890 ◽  
Author(s):  
Juan Casado ◽  
José R. Culleré ◽  
Montserrat Julià ◽  
Enrique Brillas
Keyword(s):  
Electrochemical Reduction ◽  
Gold Electrode ◽  
Ring Electrode ◽  
Allyl Radical ◽  
Rate Determining Step ◽  
Ec Mechanism ◽  
Controlled Potential ◽  
Electron Reduction ◽  
Controlled Potential Coulometry ◽  
Rotating Ring Disc Electrode

The electrochemical reduction of 1-bromo-2-butene and 1-chloro-2-butene in DMF at a Hg electrode has been studied by polarography, cyclic voltammetry (CV), a rotating ring-disc electrode and controlled-potential coulometry. A CV study using a gold electrode has also been carried out for these compounds to identify the detected intermediates. Two consecutive one-electron reduction processes are found for 1-bromo-2-butene in polarography and in CV using Hg electrode. The first process is initiated by the irreversible one-electron cleavage of the carbon-bromo bond to give the allyl radical and Br-, which is the rate-determining step. The second one follows a first-order EC mechanism, being initiated by generation of the allylmercury anion via a one-electron reduction of the allylmercury radical, previously formed by reaction of the allyl radical with Hg. A single irreversible two-electron process is found for 1-chloro-2-butene under all voltammetric conditions and for both compounds in CV using a gold electrode. Additional anodic peaks detected in CV, as well as anodic waves found at the rotating Hg ring electrode, are ascribed to oxidation of the allylmercury anion and the allyl anion.

scholarly journals Voltammetric and potentiometric studies of some sulpha drug-Schiff base compounds and their metal complexes

2007 ◽  
Vol 5 (3) ◽  
pp. 898-911 ◽  
Author(s):  
M. Ghoneim ◽  
E. Mabrouk ◽  
A. Hassanein ◽  
M. El-Attar ◽  
E. Hesham
Keyword(s):  
Schiff Bases ◽  
Reaction Pathway ◽  
Mercury Electrode ◽  
Transition Metal Ions ◽  
Electrode Reaction ◽  
Cyclic Voltammograms ◽  
Azomethine Group ◽  
Sulpha Drug ◽  
Controlled Potential ◽  
The Stability

AbstractThe electrochemical behavior of some sulpha drug-Schiff bases at a mercury electrode was examined in the Britton-Robinson universal buffer of various pH values (2.5–11.7) containing 20% v/v) of ethanol using DC-polarography, cyclic voltammetry and controlled-potential electrolysis. The DC-polarograms and cyclic voltammograms of the examined compounds exhibited a single, 2-electron, irreversible, diffusion-controlled cathodic step within the entire pH range which is attributed to the reduction of the azomethine group-CH=N- to -CH2-NH-. The symmetry transfer coefficient (α) of the electrode reaction and the diffusion coefficient (D 0) of the reactant species were determined. The electrode reaction pathway of the compounds at the mercury electrode was suggested to follow the sequence: H+, e−, e−, H+. The dissociation constant of the sulpha drug-Schiff bases, the stability constant and stoichiometry of their complexes with various divalent transition metal ions (Mn2+, Co2+, Ni2+, Cu2+ and Zn2+) were determined potentiometrically at room temperature.

scholarly journals Electrochemical Behavior of Ni(II)-Salen at the Mercury Electrode

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Pércio Augusto Mardini Farias ◽  
Margarida Bethlem Rodrigues Bastos
Keyword(s):  
Electron Transfer ◽  
Detection Limit ◽  
Aqueous Media ◽  
Mercury Electrode ◽  
Stripping Voltammetry ◽  
Mean Value ◽  
Cathodic Stripping Voltammetry ◽  
Ec Mechanism ◽  
Nickel Determination ◽  
The Mean

The complex Ni(II)-salen has been studied using cyclic and square-wave cathodic stripping voltammetry at the static mercury drop electrode in an aqueous media of phosphate and Hepes buffers (at pH 7.0). The resulting voltammograms consist of a totally irreversible one-electron transfer attributable to the coupling of Ni(II) salen/Ni(I) salen via an EC mechanism. The mean value for the transfer coefficientαin both supporting electrolytes was calculated as 0.35 ± 0.05. The amount of reactant adsorbed after 60 s of accumulation at −700 mV was calculated to be 2.8 × 10−8 mol·cm−2. The detection limit for nickel determination was found to be 3.4 × 10−9 mol L−1.

Regioselective S—O vs. C—O bond cleavage in sulfenate ester radical anions

2005 ◽  
Vol 83 (9) ◽  
pp. 1473-1482 ◽  
Author(s):  
Donald LB Stringle ◽  
Mark S Workentin
Keyword(s):  
Electron Transfer ◽  
Bond Cleavage ◽  
Electrochemical Techniques ◽  
Radical Anions ◽  
Peak Potential ◽  
Dissociative Mechanism ◽  
Dissociative Electron Transfer ◽  
Controlled Potential Electrolysis ◽  
Controlled Potential ◽  
Singly Occupied Molecular Orbitals

The electron transfer (ET) reduction of benzyl benzenesulfenate ester (1) and tert-butyl benzenesulfenate ester (2) was investigated using electrochemical techniques. Analysis of the cyclic voltammetry of each compound suggests that the ET reduction proceeds via a stepwise dissociative mechanism. The voltammograms of 1 are similar to those of diaryl disulfides and it was found through controlled potential electrolysis (CPE) product studies that ET reduction leads to S—O bond cleavage. The voltammograms of 2 are dramatically different with a sharper dissociative wave occurring at a more negative peak potential. CPE experiments indicate products that result from ET leading to C—O bond cleavage in this case. DFT calculations of the singly occupied molecular orbitals (SOMOs) of 1 and 2 were performed and offer a rationale for the different reactivity of the two radical anions.Key words: sulfenate esters, dissociative electron transfer, electrochemistry, radical anions.

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