Claudio Tavagnacco - Academia.edu (original) (raw)

Papers by Claudio Tavagnacco

Research paper thumbnail of Electrochemistry of dioxygen activation in the presence of adenine

Inorganica Chimica Acta, Oct 1, 1998

Abstract The electrochemical behavior of dioxygen in the presence of adenine in dimethylformamide... more Abstract The electrochemical behavior of dioxygen in the presence of adenine in dimethylformamide solution on the Hg electrode is studied. Evidence for the activation of O 2 is given by the shift of 150 mV towards more positive values of the one-electron reduction, accompanied by the autooxidation of adenine, while the adsorption of O 2 is shown by the characteristics of a polarographic pre-wave and voltammetric peak. The activation of O 2 is attributed to the interaction with adenine co-adsorbed on the Hg electrode.

Research paper thumbnail of Synthesis, Characterization, and Electrochemical Properties of Dinuclear Complexes Assembled from Asymmetric Co <sup>III</sup> Bis(dioximates) and Boronic Acids

European Journal of Inorganic Chemistry, Sep 22, 2005

Bis(methylphenylglyoximate)cobalt(III) complexes exist both as cis and trans isomers due to the a... more Bis(methylphenylglyoximate)cobalt(III) complexes exist both as cis and trans isomers due to the asymmetry of the equatorial ligand, and, when the axial ligands are different, the trans isomer is chiral. The reaction of racemic trans‐[CH3Co(mpgH)2py] (1) with either 3‐ or 4‐pyridylboronic acid affords dimeric units arranged on a crystallographic symmetry center such that the pyridyl nitrogen of one moiety coordinates to the Co atom of the symmetry‐related unit. In principle, three structurally different dimeric species (two homodimers and one heterodimer) can be obtained. Time‐resolved 1H NMR spectra of a 1:1 mixture of racemic 1 and either 3‐ or 4‐pyridylboronic acid in CDCl3/CD3OD show that the reaction does not converge toward a unique species in solution. Nevertheless, X‐ray structures show that the heterochiral dimers are the only products that crystallize from the reaction mixture. The nature of the dioximate side groups does not affect the geometry of the dimeric arrangements assembled by 4‐pyridylboronic acid (“molecular box”). On the contrary, the geometry of the species assembled by 3‐pyridylboronic acid varies from the “molecular parallelogram” obtained from the bis(dimethylglyoximates) to the highly squeezed “molecular box” obtained from bis(methylphenylglyoximates). Cyclic voltammetry studies show that the metal centers in the dimeric species do not interact with each other and undergo a simultaneous redox process. However, depending on the geometry of the systems, the redox process involves a single four‐electron reduction for 3 and 5 or two consecutive two‐electron reduction steps for 4 and 6. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2005)

Research paper thumbnail of Carbon Nanotubes, Directly Grown on Supporting Surfaces, Improve Neuronal Activity in Hippocampal Neuronal Networks

Advanced biosystems, Mar 25, 2019

Research paper thumbnail of Selective Electrocatalytic H <sub>2</sub> O <sub>2</sub> Generation by Cobalt@N‐Doped Graphitic Carbon Core–Shell Nanohybrids

Chemsuschem, Mar 21, 2019

Electrocatalytic oxygen reduction (ORR) is an emerging synthetic strategy to prepare H2O2 in a su... more Electrocatalytic oxygen reduction (ORR) is an emerging synthetic strategy to prepare H2O2 in a sustainable fashion. N‐doped graphitic carbon with embedded cobalt nanoparticles was selected as an advanced material able to selectively trigger the ORR to form H2O2 with a faradaic efficiency of almost 100 % at very positive applied potentials. The production of H2O2 proceeded with high rates as calculated by bulk electrolysis (49 mmol g−1 h−1) and excellent current densities (≈−0.8 mA cm−2 at 0.5 V vs. reversible hydrogen electrode). The totally selective behavior depended on the combination of concomitant material features, such as the textural properties, the nature of the metal, the distribution of N moieties, the acidic environment, and the applied potential.

Research paper thumbnail of ChemInform Abstract: Transition-Metal NMR Spectroscopy. Part 14. Electronic and Steric Influence of Axial and Equatorial Ligands in Vitamin B12 Model Complexes (I)-(IV) Derived from Cobaloxime: Electrochemical and 59Co-NMR Studies

ChemInform, Nov 27, 1990

ChemInform Abstract 1H, 13C, and 57Fe NMR spectra are reported for 73 olefinic and allylic organo... more ChemInform Abstract 1H, 13C, and 57Fe NMR spectra are reported for 73 olefinic and allylic organoiron complexes of the type shown in the scheme. H,H, C,H, and C,C coupling constants are evaluated and are analyzed in terms of the geometry of the coordinated diene. The results are corroborated by the crystal structure determination for (VI) (space group P1, Z=2), which shows an unusual distortion of the Me2C group. A number of the complexes are synthesized (yields given). Dienes with (Z)-configurated terminal Me group show steric inhibition of metal complexation resulting in lower yields and the formation of η2-diene complexes as additional products, as demonstrated for (VIII) (→ (IX) and (X)). Regioselective attack by C-nucleophiles at the carbonyl C-atom of the functional group with or without concomitant 1,3 migration of the Fe(CO)3 group is used to synthesize polyenes and isoprenoid building blocks for the complexes. Wittig-Horner-type reactions are also used for the complex synthesis.

Research paper thumbnail of Interaction of Molecular Oxygen with Transition Metal Centers in Electrocatalytic Synthesis of Peroxo Species

Studies in Surface Science and Catalysis, 1991

Publisher Summary Transition metal complexes are widely used as models, either of oxygen carriers... more Publisher Summary Transition metal complexes are widely used as models, either of oxygen carriers or of catalysts for biological and industrial oxidations. The key factors determining the oxygen carrying or the catalytic properties are the thermodynamic and kinetic features of the reaction of molecular oxygen with the metal center, which, in the case of oxygen carriers yields a relatively stable oxygen adduct, while, in the case of catalytic oxidations, the actual mechanism and the nature of the interaction between molecular oxygen and the metal center in a transition metal complex are much more elusive. This interaction is the key step also in the electrocatalytic reduction of molecular oxygen in the presence o f transition metals or transition metal complexes, taking place in the bulk of the solution or at the electrode surface, respectively. Catalytic efficiency, though demanding high reactivity of the product of the interaction between molecular oxygen and the transition metal complex, obviously does not require substantial amounts of this product which is actually the very reactive intermediate. The problem thus is to provide evidence for the coupling of the reduction of the transition metal complex with the reaction with molecular oxygen, yielding the active intermediate, and for possible formation of an unstable oxygen adduct, undergoing fast reactions.

Research paper thumbnail of Electrochemistry of 4,6-dimethyl-2-thiopyrimidine and 4,6-dimethyl-1-phenyl-2-thiopyrimidine in dimethylformamide

Journal of Electroanalytical Chemistry, 1994

Abstract The electrochemical behaviour of 4,6-dimethyl-2-thiopyrimidine (LH) and 4,6-dimethyl-1-p... more Abstract The electrochemical behaviour of 4,6-dimethyl-2-thiopyrimidine (LH) and 4,6-dimethyl-1-phenyl-2-thiopyrimidine (LΦ) and their protonated forms was investigated in dimethylformamide on Hg electrodes. Adsorption processes affect the oxidation mechanism of both the compounds and the formation of Hg(I) complexes was observed. The electrochemical reduction of LH provides an example of the so-called “father—son reaction” but this kind of mechanism cannot occur with LΦ. Only in the species LH is a proton present which can be abstracted by the product of the first electron transfer LH · − while LΦ can be protonated by the solvent. However, in the presence of strong acids, for both molecules LH and LΦ the formation of the dimer from the radical anion obtained in the first electron transfer is kinetically preferred to the father—son reaction.

Research paper thumbnail of Electrochemistry of iridium chelates with phenanthroline or substituted phenanthroline and cyclooctadiene

Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1989

The electrochemistry of a series of iridium chelates with phenanthroline or substituted phenanthr... more The electrochemistry of a series of iridium chelates with phenanthroline or substituted phenanthroline and cyclooctadiene on Hg, Pt, Au and glassy carbon electrodes is reported. Two quasi-reversible one-electron reductions between-0.8 and-1.1 V and between-1.25 and-1.55 V vs. a saturated calomel electrode were studied. Adsorption and a slow chemical reaction following the electron transfer were observed. The relationship between the reduction potentials of the chelates and those of the corresponding free phenanthroline ligands, as well as the shifts of the reduction potential caused by substitution, shows that the redox orbital is a rr * ligand orbital. This explains the lack of correlation between the redox potentials and the molecular properttes determined by the central metal atom such as the catalytic efficiency.

Research paper thumbnail of Voltammetric, Raman, ans SERRS Study of the Complex Cytochrome c/Cardiolipin and its Implications in the Apoptosis Initiation

Research paper thumbnail of Electrochemistry of 2-thio- and 2-oxo-pyrimidines in dimethyl formamide in the presence of dioxygen

Inorganica Chimica Acta, 1998

Abstract Electrocatalysis of dioxygen reduction to superoxide ion in dimethylformamide is afforde... more Abstract Electrocatalysis of dioxygen reduction to superoxide ion in dimethylformamide is afforded by a reversible interaction with thiol or hydroxo forms of pyrimidine which takes place only on the mercury surface electrode even in the absence of transition metal ions. The interaction is revealed by a polarographic wave and by a voltammetric peak which can be recorded only in the presence of dioxygen in the pyrimidines solution. The polarographic wave and voltammetric peak are attributed to the reduction of the oxygenated pyrimidine. In the range of concentration where the polarographic limiting currents due to the reduction of the oxygenated and unoxygenated pyrimidine are of the same order of magnitude, the stoichiometric ratio dioxygen/pyrimidine is determined to be 1. The electrode process probably involves the formation of a complex of mercury with the thiol or the hydroxo form of the pyrimidine on the electrode surface. Adsorption or coadsorption of the reactants seems to be involved.

Research paper thumbnail of Synthesis, characterization, and electrochemical properties of a new series of inorganic and organometallic Co(III) complexes with a Schiff base ligand derived from tyrosine

Inorganica Chimica Acta

A new series of inorganic and organometallic cobalt Schiff base complexes containing the tetraden... more A new series of inorganic and organometallic cobalt Schiff base complexes containing the tetradentate ligand {[Z-Tyr(3-Ac)-OMe]2en} derived from the condensation of two equivalents of protected 3-acetyl-l-tyrosine with one equivalent of ethylenediamine has been synthesized. As the amino acids have l configuration, the resulting ligand is chiral. The complexes have been characterized by 1H and 13C NMR, ESI-MS spectrometry and UV–Vis spectroscopy. The UV–Vis spectra recorded in CH2Cl2 show an absorption band at about 650 nm, characteristic of penta-coordinated alkylcobalt(III)(salen), but an evident deviation from the Lambert Beer law in the concentration range 0.20–2.0 × 10−3 M suggests some kind of association in this solvent. In coordinating solvent the complexes are hexa-coordinated. The equilibrium constants for pyridine ligation in CH3OH decrease with increasing electron-donor power of the axial alkyl group. Cyclic voltammetry studies indicate that after the reduction RCo(III)/R...

Research paper thumbnail of Simultaneous Quantification of Antioxidants Paraxanthine and Caffeine in Human Saliva by Electrochemical Sensing for CYP1A2 Phenotyping

Antioxidants, 2020

The enzyme CYP1A2 is responsible for the metabolism of numerous antioxidants in the body, includi... more The enzyme CYP1A2 is responsible for the metabolism of numerous antioxidants in the body, including caffeine, which is transformed into paraxanthine, its main primary metabolite. Both molecules are known for their antioxidant and pro-oxidant characteristics, and the paraxanthine-to-caffeine molar ratio is a widely accepted metric for CYP1A2 phenotyping, to optimize dose–response effects in individual patients. We developed a simple, cheap and fast electrochemical based method for the simultaneous quantification of paraxanthine and caffeine in human saliva, by differential pulse voltammetry, using an anodically pretreated glassy carbon electrode. Cyclic voltammetry experiments revealed for the first time that the oxidation of paraxanthine is diffusion controlled with an irreversible peak at ca. +1.24 V (vs. Ag/AgCl) in a 0.1 M H2SO4 solution, and that the mechanism occurs via the transfer of two electrons and two protons. The simultaneous quantification of paraxanthine and caffeine w...

Research paper thumbnail of Energetics of Heavy Metal-Thioether Interactions in Solution and Gas Phase

Research paper thumbnail of Pd@TiO2/carbon nanohorn electrocatalysts: reversible CO2 hydrogenation to formic acid

Energy & Environmental Science, 2018

Direct conversion of carbon dioxide to formic acid at thermodynamic equilibrium is an advantage o... more Direct conversion of carbon dioxide to formic acid at thermodynamic equilibrium is an advantage of enzymatic catalysis, hardly replicated by synthetic analogs, but of high priority for carbon-neutral energy schemes.

Research paper thumbnail of N-Doped Graphitized Carbon Nanohorns as a Forefront Electrocatalyst in Highly Selective O2 Reduction to H2O2

Chem, 2018

Fornasiero and colleagues describe an alternative strategy for producing hydrogen peroxide throug... more Fornasiero and colleagues describe an alternative strategy for producing hydrogen peroxide through a more sustainable method than the current synthetic approaches. The strategy relies on the use of electrocatalysis, made possible by the use of a catalyst with high efficiency and selectivity toward H 2 O 2 formation. The prepared material is particularly appealing because it does not contain any metal, implying a greener and cheaper synthetic scheme.

Research paper thumbnail of Electrochemical investigation of molecular oxygen interaction with iridium(I) complexes

Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1989

The interaction between molecular oxygen and an iridium(I) chelate containing methyl-substituted ... more The interaction between molecular oxygen and an iridium(I) chelate containing methyl-substituted phenanthroline and cyclooctadiene has been investigated by means of cyclic voltammetric and spectrophotometric techniques. Evidence is presented for the formation of an adduct, which decomposes irreversibly in solution leading to autoxidation, but gives rise to a kinetic reduction peak at a stationary mercury electrode. T'he very fast homogeneous reaction between the complex and the superoxide anion is also discussed.

Research paper thumbnail of Electrochemistry of sodium trans-bis(dimethyl sulphoxide) tetrachlororuthenate(III) and mer-trichlorotris(dimethyl sulphoxide) ruthenium(III): the first and complete electrochemical characterization of chlorodimethyl sulphoxide ruthenium(III) complexes

Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1990

... Chem. 38 (1976), p. 1815. 4T. Bora and MM Singh, Transition Met. Chem. (Weinheim) 3 (1978), p... more ... Chem. 38 (1976), p. 1815. 4T. Bora and MM Singh, Transition Met. Chem. (Weinheim) 3 (1978), p. 27. Full Text via CrossRef. 5P.G. Antonov, Yu.N. Kukushkin, VI Konnov and Yu.P. Kostikov, Koord. Khim. 6 (1980), p. 1585. 6H.A. Hudaly, JV Kingston and HA Tayim, Inorg. Chem. ...

Research paper thumbnail of Investigation of the kinetic behaviour of captopril followed by A.C. polarography

Journal of the Chemical Society, Faraday Transactions, 1991

... Paolo Passamonti,* Stefan0 Ferraro and Filippo Pucciarelli Dipartimento di Scienze Chimiche V... more ... Paolo Passamonti,* Stefan0 Ferraro and Filippo Pucciarelli Dipartimento di Scienze Chimiche Via Sant 'Agostino, 1-62032 Camerino (MC) , Italy Claudio Tavagnacco Dipartimento di Scienze Chimiche Via Valerio, 3834 127 Trieste, Italy 3505 by AC ... The plot of cot g 4 us. ...

Research paper thumbnail of Redox thermodynamics of cytochrome c in mixed water–organic solvent solutions

Inorganica Chimica Acta, 2003

Bovine heart cytochrome c was studied through cyclic voltammetry in mixed water Á/organic solvent... more Bovine heart cytochrome c was studied through cyclic voltammetry in mixed water Á/organic solvent solutions under different conditions of temperature and the thermodynamic properties DS 8 rc and DH 8 rc calculated by the dependence of E 8 by temperature. The effect of the organic fraction of the solvent on the E 8 values of the native cyt c was found to be determined mainly by the decrease in dielectric constant of the medium. Specific interactions on the protein surface do not seem to play a remarkable role. The thermodynamic properties changes induced by the organic fraction have been interpreted tentatively in terms of solvation properties of cytochrome c and structural features of the protein environment.

Research paper thumbnail of Cationic rhodium(III) bisdimethylglyoximates with water and triphenylphosphine axial ligands

Inorganica Chimica Acta, 1997

Preparations of [Rh(Hdmg)Z(HzO)z]CIO~ (1) (Hdmg=dimethylgyonim) from [Rh(H,O),](CIO,), anddimed~y... more Preparations of [Rh(Hdmg)Z(HzO)z]CIO~ (1) (Hdmg=dimethylgyonim) from [Rh(H,O),](CIO,), anddimed~ylgJyoxir [Rb(Hdmg),(PPb,)zlCIO~ (2) from 1 and PPhl arc described. 1 crystallizes in the CL/c space group with (I= 14.910(3). b=6.058(I). c= 18.617(4) A, p= 107.649(S)", 2~4. The structure was refined up to R=O.G21 for 1849 r&ctioas. The IR and NMR specaa elecuochemicalbehaviorof land2arediscussedandcomp~d~~~~~~~s.~~l~~~c~~~~~ for 2. the first two, rqcctively to Rh(Il) sad Rh(I), being followed by fast reactions.

Research paper thumbnail of Electrochemistry of dioxygen activation in the presence of adenine

Inorganica Chimica Acta, Oct 1, 1998

Abstract The electrochemical behavior of dioxygen in the presence of adenine in dimethylformamide... more Abstract The electrochemical behavior of dioxygen in the presence of adenine in dimethylformamide solution on the Hg electrode is studied. Evidence for the activation of O 2 is given by the shift of 150 mV towards more positive values of the one-electron reduction, accompanied by the autooxidation of adenine, while the adsorption of O 2 is shown by the characteristics of a polarographic pre-wave and voltammetric peak. The activation of O 2 is attributed to the interaction with adenine co-adsorbed on the Hg electrode.

Research paper thumbnail of Synthesis, Characterization, and Electrochemical Properties of Dinuclear Complexes Assembled from Asymmetric Co <sup>III</sup> Bis(dioximates) and Boronic Acids

European Journal of Inorganic Chemistry, Sep 22, 2005

Bis(methylphenylglyoximate)cobalt(III) complexes exist both as cis and trans isomers due to the a... more Bis(methylphenylglyoximate)cobalt(III) complexes exist both as cis and trans isomers due to the asymmetry of the equatorial ligand, and, when the axial ligands are different, the trans isomer is chiral. The reaction of racemic trans‐[CH3Co(mpgH)2py] (1) with either 3‐ or 4‐pyridylboronic acid affords dimeric units arranged on a crystallographic symmetry center such that the pyridyl nitrogen of one moiety coordinates to the Co atom of the symmetry‐related unit. In principle, three structurally different dimeric species (two homodimers and one heterodimer) can be obtained. Time‐resolved 1H NMR spectra of a 1:1 mixture of racemic 1 and either 3‐ or 4‐pyridylboronic acid in CDCl3/CD3OD show that the reaction does not converge toward a unique species in solution. Nevertheless, X‐ray structures show that the heterochiral dimers are the only products that crystallize from the reaction mixture. The nature of the dioximate side groups does not affect the geometry of the dimeric arrangements assembled by 4‐pyridylboronic acid (“molecular box”). On the contrary, the geometry of the species assembled by 3‐pyridylboronic acid varies from the “molecular parallelogram” obtained from the bis(dimethylglyoximates) to the highly squeezed “molecular box” obtained from bis(methylphenylglyoximates). Cyclic voltammetry studies show that the metal centers in the dimeric species do not interact with each other and undergo a simultaneous redox process. However, depending on the geometry of the systems, the redox process involves a single four‐electron reduction for 3 and 5 or two consecutive two‐electron reduction steps for 4 and 6. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2005)

Research paper thumbnail of Carbon Nanotubes, Directly Grown on Supporting Surfaces, Improve Neuronal Activity in Hippocampal Neuronal Networks

Advanced biosystems, Mar 25, 2019

Research paper thumbnail of Selective Electrocatalytic H <sub>2</sub> O <sub>2</sub> Generation by Cobalt@N‐Doped Graphitic Carbon Core–Shell Nanohybrids

Chemsuschem, Mar 21, 2019

Electrocatalytic oxygen reduction (ORR) is an emerging synthetic strategy to prepare H2O2 in a su... more Electrocatalytic oxygen reduction (ORR) is an emerging synthetic strategy to prepare H2O2 in a sustainable fashion. N‐doped graphitic carbon with embedded cobalt nanoparticles was selected as an advanced material able to selectively trigger the ORR to form H2O2 with a faradaic efficiency of almost 100 % at very positive applied potentials. The production of H2O2 proceeded with high rates as calculated by bulk electrolysis (49 mmol g−1 h−1) and excellent current densities (≈−0.8 mA cm−2 at 0.5 V vs. reversible hydrogen electrode). The totally selective behavior depended on the combination of concomitant material features, such as the textural properties, the nature of the metal, the distribution of N moieties, the acidic environment, and the applied potential.

Research paper thumbnail of ChemInform Abstract: Transition-Metal NMR Spectroscopy. Part 14. Electronic and Steric Influence of Axial and Equatorial Ligands in Vitamin B12 Model Complexes (I)-(IV) Derived from Cobaloxime: Electrochemical and 59Co-NMR Studies

ChemInform, Nov 27, 1990

ChemInform Abstract 1H, 13C, and 57Fe NMR spectra are reported for 73 olefinic and allylic organo... more ChemInform Abstract 1H, 13C, and 57Fe NMR spectra are reported for 73 olefinic and allylic organoiron complexes of the type shown in the scheme. H,H, C,H, and C,C coupling constants are evaluated and are analyzed in terms of the geometry of the coordinated diene. The results are corroborated by the crystal structure determination for (VI) (space group P1, Z=2), which shows an unusual distortion of the Me2C group. A number of the complexes are synthesized (yields given). Dienes with (Z)-configurated terminal Me group show steric inhibition of metal complexation resulting in lower yields and the formation of η2-diene complexes as additional products, as demonstrated for (VIII) (→ (IX) and (X)). Regioselective attack by C-nucleophiles at the carbonyl C-atom of the functional group with or without concomitant 1,3 migration of the Fe(CO)3 group is used to synthesize polyenes and isoprenoid building blocks for the complexes. Wittig-Horner-type reactions are also used for the complex synthesis.

Research paper thumbnail of Interaction of Molecular Oxygen with Transition Metal Centers in Electrocatalytic Synthesis of Peroxo Species

Studies in Surface Science and Catalysis, 1991

Publisher Summary Transition metal complexes are widely used as models, either of oxygen carriers... more Publisher Summary Transition metal complexes are widely used as models, either of oxygen carriers or of catalysts for biological and industrial oxidations. The key factors determining the oxygen carrying or the catalytic properties are the thermodynamic and kinetic features of the reaction of molecular oxygen with the metal center, which, in the case of oxygen carriers yields a relatively stable oxygen adduct, while, in the case of catalytic oxidations, the actual mechanism and the nature of the interaction between molecular oxygen and the metal center in a transition metal complex are much more elusive. This interaction is the key step also in the electrocatalytic reduction of molecular oxygen in the presence o f transition metals or transition metal complexes, taking place in the bulk of the solution or at the electrode surface, respectively. Catalytic efficiency, though demanding high reactivity of the product of the interaction between molecular oxygen and the transition metal complex, obviously does not require substantial amounts of this product which is actually the very reactive intermediate. The problem thus is to provide evidence for the coupling of the reduction of the transition metal complex with the reaction with molecular oxygen, yielding the active intermediate, and for possible formation of an unstable oxygen adduct, undergoing fast reactions.

Research paper thumbnail of Electrochemistry of 4,6-dimethyl-2-thiopyrimidine and 4,6-dimethyl-1-phenyl-2-thiopyrimidine in dimethylformamide

Journal of Electroanalytical Chemistry, 1994

Abstract The electrochemical behaviour of 4,6-dimethyl-2-thiopyrimidine (LH) and 4,6-dimethyl-1-p... more Abstract The electrochemical behaviour of 4,6-dimethyl-2-thiopyrimidine (LH) and 4,6-dimethyl-1-phenyl-2-thiopyrimidine (LΦ) and their protonated forms was investigated in dimethylformamide on Hg electrodes. Adsorption processes affect the oxidation mechanism of both the compounds and the formation of Hg(I) complexes was observed. The electrochemical reduction of LH provides an example of the so-called “father—son reaction” but this kind of mechanism cannot occur with LΦ. Only in the species LH is a proton present which can be abstracted by the product of the first electron transfer LH · − while LΦ can be protonated by the solvent. However, in the presence of strong acids, for both molecules LH and LΦ the formation of the dimer from the radical anion obtained in the first electron transfer is kinetically preferred to the father—son reaction.

Research paper thumbnail of Electrochemistry of iridium chelates with phenanthroline or substituted phenanthroline and cyclooctadiene

Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1989

The electrochemistry of a series of iridium chelates with phenanthroline or substituted phenanthr... more The electrochemistry of a series of iridium chelates with phenanthroline or substituted phenanthroline and cyclooctadiene on Hg, Pt, Au and glassy carbon electrodes is reported. Two quasi-reversible one-electron reductions between-0.8 and-1.1 V and between-1.25 and-1.55 V vs. a saturated calomel electrode were studied. Adsorption and a slow chemical reaction following the electron transfer were observed. The relationship between the reduction potentials of the chelates and those of the corresponding free phenanthroline ligands, as well as the shifts of the reduction potential caused by substitution, shows that the redox orbital is a rr * ligand orbital. This explains the lack of correlation between the redox potentials and the molecular properttes determined by the central metal atom such as the catalytic efficiency.

Research paper thumbnail of Voltammetric, Raman, ans SERRS Study of the Complex Cytochrome c/Cardiolipin and its Implications in the Apoptosis Initiation

Research paper thumbnail of Electrochemistry of 2-thio- and 2-oxo-pyrimidines in dimethyl formamide in the presence of dioxygen

Inorganica Chimica Acta, 1998

Abstract Electrocatalysis of dioxygen reduction to superoxide ion in dimethylformamide is afforde... more Abstract Electrocatalysis of dioxygen reduction to superoxide ion in dimethylformamide is afforded by a reversible interaction with thiol or hydroxo forms of pyrimidine which takes place only on the mercury surface electrode even in the absence of transition metal ions. The interaction is revealed by a polarographic wave and by a voltammetric peak which can be recorded only in the presence of dioxygen in the pyrimidines solution. The polarographic wave and voltammetric peak are attributed to the reduction of the oxygenated pyrimidine. In the range of concentration where the polarographic limiting currents due to the reduction of the oxygenated and unoxygenated pyrimidine are of the same order of magnitude, the stoichiometric ratio dioxygen/pyrimidine is determined to be 1. The electrode process probably involves the formation of a complex of mercury with the thiol or the hydroxo form of the pyrimidine on the electrode surface. Adsorption or coadsorption of the reactants seems to be involved.

Research paper thumbnail of Synthesis, characterization, and electrochemical properties of a new series of inorganic and organometallic Co(III) complexes with a Schiff base ligand derived from tyrosine

Inorganica Chimica Acta

A new series of inorganic and organometallic cobalt Schiff base complexes containing the tetraden... more A new series of inorganic and organometallic cobalt Schiff base complexes containing the tetradentate ligand {[Z-Tyr(3-Ac)-OMe]2en} derived from the condensation of two equivalents of protected 3-acetyl-l-tyrosine with one equivalent of ethylenediamine has been synthesized. As the amino acids have l configuration, the resulting ligand is chiral. The complexes have been characterized by 1H and 13C NMR, ESI-MS spectrometry and UV–Vis spectroscopy. The UV–Vis spectra recorded in CH2Cl2 show an absorption band at about 650 nm, characteristic of penta-coordinated alkylcobalt(III)(salen), but an evident deviation from the Lambert Beer law in the concentration range 0.20–2.0 × 10−3 M suggests some kind of association in this solvent. In coordinating solvent the complexes are hexa-coordinated. The equilibrium constants for pyridine ligation in CH3OH decrease with increasing electron-donor power of the axial alkyl group. Cyclic voltammetry studies indicate that after the reduction RCo(III)/R...

Research paper thumbnail of Simultaneous Quantification of Antioxidants Paraxanthine and Caffeine in Human Saliva by Electrochemical Sensing for CYP1A2 Phenotyping

Antioxidants, 2020

The enzyme CYP1A2 is responsible for the metabolism of numerous antioxidants in the body, includi... more The enzyme CYP1A2 is responsible for the metabolism of numerous antioxidants in the body, including caffeine, which is transformed into paraxanthine, its main primary metabolite. Both molecules are known for their antioxidant and pro-oxidant characteristics, and the paraxanthine-to-caffeine molar ratio is a widely accepted metric for CYP1A2 phenotyping, to optimize dose–response effects in individual patients. We developed a simple, cheap and fast electrochemical based method for the simultaneous quantification of paraxanthine and caffeine in human saliva, by differential pulse voltammetry, using an anodically pretreated glassy carbon electrode. Cyclic voltammetry experiments revealed for the first time that the oxidation of paraxanthine is diffusion controlled with an irreversible peak at ca. +1.24 V (vs. Ag/AgCl) in a 0.1 M H2SO4 solution, and that the mechanism occurs via the transfer of two electrons and two protons. The simultaneous quantification of paraxanthine and caffeine w...

Research paper thumbnail of Energetics of Heavy Metal-Thioether Interactions in Solution and Gas Phase

Research paper thumbnail of Pd@TiO2/carbon nanohorn electrocatalysts: reversible CO2 hydrogenation to formic acid

Energy & Environmental Science, 2018

Direct conversion of carbon dioxide to formic acid at thermodynamic equilibrium is an advantage o... more Direct conversion of carbon dioxide to formic acid at thermodynamic equilibrium is an advantage of enzymatic catalysis, hardly replicated by synthetic analogs, but of high priority for carbon-neutral energy schemes.

Research paper thumbnail of N-Doped Graphitized Carbon Nanohorns as a Forefront Electrocatalyst in Highly Selective O2 Reduction to H2O2

Chem, 2018

Fornasiero and colleagues describe an alternative strategy for producing hydrogen peroxide throug... more Fornasiero and colleagues describe an alternative strategy for producing hydrogen peroxide through a more sustainable method than the current synthetic approaches. The strategy relies on the use of electrocatalysis, made possible by the use of a catalyst with high efficiency and selectivity toward H 2 O 2 formation. The prepared material is particularly appealing because it does not contain any metal, implying a greener and cheaper synthetic scheme.

Research paper thumbnail of Electrochemical investigation of molecular oxygen interaction with iridium(I) complexes

Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1989

The interaction between molecular oxygen and an iridium(I) chelate containing methyl-substituted ... more The interaction between molecular oxygen and an iridium(I) chelate containing methyl-substituted phenanthroline and cyclooctadiene has been investigated by means of cyclic voltammetric and spectrophotometric techniques. Evidence is presented for the formation of an adduct, which decomposes irreversibly in solution leading to autoxidation, but gives rise to a kinetic reduction peak at a stationary mercury electrode. T'he very fast homogeneous reaction between the complex and the superoxide anion is also discussed.

Research paper thumbnail of Electrochemistry of sodium trans-bis(dimethyl sulphoxide) tetrachlororuthenate(III) and mer-trichlorotris(dimethyl sulphoxide) ruthenium(III): the first and complete electrochemical characterization of chlorodimethyl sulphoxide ruthenium(III) complexes

Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1990

... Chem. 38 (1976), p. 1815. 4T. Bora and MM Singh, Transition Met. Chem. (Weinheim) 3 (1978), p... more ... Chem. 38 (1976), p. 1815. 4T. Bora and MM Singh, Transition Met. Chem. (Weinheim) 3 (1978), p. 27. Full Text via CrossRef. 5P.G. Antonov, Yu.N. Kukushkin, VI Konnov and Yu.P. Kostikov, Koord. Khim. 6 (1980), p. 1585. 6H.A. Hudaly, JV Kingston and HA Tayim, Inorg. Chem. ...

Research paper thumbnail of Investigation of the kinetic behaviour of captopril followed by A.C. polarography

Journal of the Chemical Society, Faraday Transactions, 1991

... Paolo Passamonti,* Stefan0 Ferraro and Filippo Pucciarelli Dipartimento di Scienze Chimiche V... more ... Paolo Passamonti,* Stefan0 Ferraro and Filippo Pucciarelli Dipartimento di Scienze Chimiche Via Sant 'Agostino, 1-62032 Camerino (MC) , Italy Claudio Tavagnacco Dipartimento di Scienze Chimiche Via Valerio, 3834 127 Trieste, Italy 3505 by AC ... The plot of cot g 4 us. ...

Research paper thumbnail of Redox thermodynamics of cytochrome c in mixed water–organic solvent solutions

Inorganica Chimica Acta, 2003

Bovine heart cytochrome c was studied through cyclic voltammetry in mixed water Á/organic solvent... more Bovine heart cytochrome c was studied through cyclic voltammetry in mixed water Á/organic solvent solutions under different conditions of temperature and the thermodynamic properties DS 8 rc and DH 8 rc calculated by the dependence of E 8 by temperature. The effect of the organic fraction of the solvent on the E 8 values of the native cyt c was found to be determined mainly by the decrease in dielectric constant of the medium. Specific interactions on the protein surface do not seem to play a remarkable role. The thermodynamic properties changes induced by the organic fraction have been interpreted tentatively in terms of solvation properties of cytochrome c and structural features of the protein environment.

Research paper thumbnail of Cationic rhodium(III) bisdimethylglyoximates with water and triphenylphosphine axial ligands

Inorganica Chimica Acta, 1997

Preparations of [Rh(Hdmg)Z(HzO)z]CIO~ (1) (Hdmg=dimethylgyonim) from [Rh(H,O),](CIO,), anddimed~y... more Preparations of [Rh(Hdmg)Z(HzO)z]CIO~ (1) (Hdmg=dimethylgyonim) from [Rh(H,O),](CIO,), anddimed~ylgJyoxir [Rb(Hdmg),(PPb,)zlCIO~ (2) from 1 and PPhl arc described. 1 crystallizes in the CL/c space group with (I= 14.910(3). b=6.058(I). c= 18.617(4) A, p= 107.649(S)", 2~4. The structure was refined up to R=O.G21 for 1849 r&ctioas. The IR and NMR specaa elecuochemicalbehaviorof land2arediscussedandcomp~d~~~~~~~s.~~l~~~c~~~~~ for 2. the first two, rqcctively to Rh(Il) sad Rh(I), being followed by fast reactions.