Electrocatalysis at a Conducting Composite Electrode Doped with a Ruthenium(II) Metallodendrimer

Abstract

A pentaerythritol-based metallodendrimer with RuIIterpyridine units was synthesized and tested as a mediator for the electrochemical oxidation of methionine (L-Met), cystine (L-Cys), and AsIII. A reversible oxidation of RuII was observed with the metallodendrimer as a solute in mixed acetonitrile-water solvents and as a component of carbon-based conducting composite electrodes. Mediated oxidation of the test species was observed. In aqueous solution, the composite electrode yielded a cyclic voltammetric peak current for the oxidation of L-Met in a 0.1 M phosphate buffer (pH 7.0) at 1.1 V vs Ag/AgCl. This anodic process was employed for amperometric detection in a flow system. Linear calibration curves were obtained over the range 1.0-10 microM Met and Cys. Using the criterion of the concentration yielding a signal 3 times the uncertainty of a blank, detection limits of 0.6 and 0.5 microM were calculated for Met and Cys, respectively. The slopes with three nominally identical electrodes varied by 10%.

Electrocatalytic Oxidation of Sulfur Containing Amino Acids at Renewable Ni‐Powder Doped Carbon Ceramic Electrode: Application to Amperometric Detection L‐Cystine, L‐Cysteine and L‐Methionine

“…The linear concentration range, sensitivity and detection limit for l-methionine and lcysteine determination were 2 -90 mM, 5.6 mA/mM, 2 mM and 2 -75 mM, 8.1 mA/mM and 0.2 mM, respectively. These analytical parameters are comparable or better than results that reported for analytical determination of selected analytes at the surface of different modified electrodes such as, carbon composite and glassy carbon electrodes modified with Ru(II) metallodendrimer [14,15], dirhodium-substituted polyoxometalate anchored in a xerogel based composite [16] and colloid-gold cysteamine modified carbon paste electrode [17]. The Ni powder doped CCE imparts higher stability onto amperometric measurements of disulfides and l-methionine.…”

“…Although many modified electrodes have been used for detection of thiols, but few of them showed significant electrocatalytic activity for disulfides and l-methionine. Carbon composite and glassy carbon electrodes modified with Ru(II) metallodendrimer [14,15], dirhodium-substituted polyoxometalate anchored in a xerogel based composite [16], colloid-gold cysteamine modified carbon paste electrode [17] have been used for electrocatalytic oxidation and determination of l-cystine and l-methionine. Mercuryplated copper electrode, glassy carbon electrode modified with CePtCl 6 and platinum electrode modified with poly methyl violet have been used for electrocatalytic reduction of l-cystine, sulfur derivatives and sulfur oxoanions [18 -20].…”

Redox, surface and electrocatalytic properties of layer-by-layer films based upon Fe(III)-substituted crown polyoxometalate [P8W48O184Fe16(OH)28(H2O)4]20-

“…Metal ion-substituted dendrimers showed an enhancement of catalytic properties [41] and offered the sites for electron transfer mediation [42].…”

“…(Fig. 1B)) was synthesized following the method reported by Constable [47] and Holmstrom [42]. At the first stage, four terpyridine metal-binding units were attached to the pentaerythritol by the reaction with 4'-chloro-terpirydine in presence of potassium hydroxide in DMSO.…”

Dendritic Encapsulation of Redox‐Active Units

“…Many of these involve peripheral functionalization of the dendrimer with redox-active units. [38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55] These are very interesting and potentially useful architectures and may, for example, serve as new types of redox mediators, sensors, or elements of supercapacitors. Other intriguing electrochemical behaviors of dendrimers include "redox sponges," [56][57][58][59] redox gradients for "one-way" radial charge transport, 60,61 charge "trapping," 57 and dendritic insulation for molecular wires.…”