M. J. Aguirre

University of Santiago, Chile, CiudadSantiago, Santiago Metropolitan, Chile

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Publications (29)62.82 Total impact

  • R. Arce, M. J. Aguirre
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    ABSTRACT: The sulfite is commonly used antiseptic wine and food. You can find free or bound to phenols , aldehydes and other organic compounds. Its concentration at high levels produces toxic effects, such as pain when breathing in asthmatic patients , hypotension and gastrointestinal problems. Therefore it is useful to determine the electrochemically concentration , and with this, to separate , by absorbing membrane system , the other impurities present in food. Sulfite (SO3-2) in aqueous solution is in equilibrium with bisulfite ( HSO3 - ) and sulfur dioxide ( SO2) , where their concentrations depend mainly on the pH. As to the electrochemical method , the cyclic voltammetry was used. This technique is widely used and is of considerable use in the study of oxide / reduction , detection of reaction intermediates and observing reactions monitoring electrode products formed in reactions . In conjunction with the cyclic voltammetry method of calibration curve is applied and thus determine how feasible it is to implement in an electrochemical analysis. The method of calibration curve represents the response of an analytical method to known concentrations of analyte . Previous studies done in the laboratory show that it is possible to find a potential range where the SO3 -2 shows an increasing response in current and potential displacement , and in addition, all the parameters are optimized for system performance membrane absorber .
    2014 ECS and SMEQ Joint International Meeting; 10/2014
  • Journal of the Chilean Chemical Society 07/2014; 59(2):2526-2528. DOI:10.4067/S0717-97072014000200029 · 0.47 Impact Factor
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    ABSTRACT: In the present work, known concentration of sulfite aqueous solutions in the presence and absence of gallic acid was measured to corroborate the validity of modified Monier-Williams method. Free and bound-sulfite was estimated by differential pulse voltammetry. To our surprise, the modified Monier-Williams method (also known as aspiration method) showed to be very inaccurate for free-sulfite, although suitable for bound-sulfite determination. The differential pulse approach, using the standard addition method and a correction coefficient, proved to be swift, cheap, and very precise and accurate.
    The Scientific World Journal 04/2012; 2012:168148. DOI:10.1100/2012/168148 · 1.73 Impact Factor
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    ABSTRACT: This paper describes the electrochemical reduction of nitrite ion in neutral aqueous solution mediated by tetraruthenated metalloporphyrins (Co(II), Ni(II) and Zn(II)) electrostatically assembled onto a Nafion film previously adsorbed on glassy carbon or ITO electrodes. Scanning electron microscope (SEM-EDX) and transmission electron microscopy (TEM) results have shown that on ITO electrodes the macrocycles forms multiple layers with a disordered stacking orientation over the Nafion film occupying hydrophobic and hydrophilic sites in the polyelectrolyte. Atomic force microscopy (AFM) results demonstrated that the Nafion film is 35nm thick and tetraruthenated metalloporphyrins layers 190nm thick presenting a thin but compacted morphology. Scanning electrochemical microscopy (SECM) images shows that the Co(II) tetraruthenated porphyrins/Nf/GC modified electrode is more electrochemically active than their Ni and Zn analogues.These modified electrodes are able to reduce nitrite at −660mV showing enhanced reduction current and a decrease in the required overpotential compared to bare glassy carbon electrode. Controlled potential electrolysis experiments verify the production of ammonia, hydrazine and hydroxylamine at potentials where reduction of solvent is plausible demonstrating some selectivity toward the nitrite ion. Rotating disc electrode voltammetry shows that the factor that governs the kinetics of nitrite reduction is the charge propagation in the film.
    Electrochimica Acta 10/2011; 56(24):8484. DOI:10.1016/j.electacta.2011.07.057 · 4.50 Impact Factor
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    ABSTRACT: The electro-oxidation of 2-mercaptoethanol by poly-Co-tetraaminophthalocyanine (p-Co-TAPc) and poly-metal-free-tetraaminophthalocyanine (p-H2TAPc), absorbed on electrode surfaces has been investigated by UV-visible spectroelectrochemistry and electrochemical techniques. In the case of p-CoTAPc, an irreversible oxidation wave is obtained by cyclic voitammetry, whereas p-H2PcTA practically does not show activity. The foot of the oxidation, as the open circuit potential measurements indicate that the responsible redox couple is Co(II)/Co(I). The p-CoTAPc modified-electrode loses its activity after a first potential cycle. UV-visible spectroelectrochemical measurements show a charge transfer band (metal to ligand) for the p-CoTAPc between Q and Soret bands when negative potentials are applied and Co(I) is obtained. The presence of 2-mercaptoethanol promotes the appearance of the charge transfer band at open circuit potential and retain this band even at potentials as positive as +0.2V where normally the Co center is in +2 oxidation state. The permanence of a stable charge transfer band indicates the formation of a stable charge-transfer adduct between Co(I) and the thiol. This adduct would be responsible for the loss of catalytic activity for p-CoTAPc after the first oxidation cycle.
    Journal of Coordination Chemistry 03/2011; 54(3):183-191. DOI:10.1080/00958970108022634 · 2.22 Impact Factor
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    ABSTRACT: In this study, we compared four glassy carbon electrodes modified with adsorbed porphyrins of cobalt containing one, two, three, or four bis(methoxyphenyl) groups as substituents of the ligand. The aim of this work was to determine the effect of these donating groups on the electrocatalyst behavior of the modified electrodes for the reduction or oxidation of sulfite in water or in mixtures of 12% ethanol in water (v/v) at different pHs. The results showed that the modified electrodes are not catalytic toward the electro-reduction of sulfite in the whole range of pH studied (2-12). However, all the electrodes showed a catalytic toward the oxidation of sulfite at basic pHs. We found that the best catalytic system was the four-substituted porphyrin modified electrode at pH 9.8. This system performed well as an amperometric sensor for sulfite in ethanol-water mixtures and in aqueous solutions at the same pH. When the calibration curve was carried out by cyclic voltammetry, a detection limit of 0.10 mg L-1 for the four-substituted cobalt porphyrin modified electrode in water and in ethanol-water mixtures was found.
    Journal of the Chilean Chemical Society 01/2010; 55(2):253-256. DOI:10.4067/S0717-97072010000200024 · 0.38 Impact Factor
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    ABSTRACT: The aim of this work is to study four types of modification of a glassy carbon electrode by Fe(III)-tetrakis(p-tetraaminophenyl)porphyrin and determine the influence of the method of immobilization of the complex on glassy carbon in electrocatalytic properties for the sulfite and hydrogensulfite oxidation in ethanol–water. The first modification was deposition of a drop of solution containing the porphyrin on a glassy carbon electrode and evaporation of the solvent (dry-drop method). The second method was immersion of the electrode at 54°C in a solution of dimethylformamide containing the porphyrin for 2 h. The third method consisted of the same heating treatment but after formation of a chemical bond of 4-aminopyridine on the glassy carbon surface, which acts as an axial ligand for the first layer of porphyrin. The fourth method involves electropolymerization of the porphyrin on the electrode surface. Important differences in stability, the potential where the oxidation wave begins and selectivity of the electrode to sulfite or hydrogensulfite were observed. The behavior of the polymer-modified electrode is different in water compared to ethanol–water.
    Journal of Coordination Chemistry 09/2009; 62(17-17):2782-2791. DOI:10.1080/00958970902942982 · 2.22 Impact Factor
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    ABSTRACT: A neutral fraction (PS-SI) (0.3g/L) with MW of 74kDa, which contained galactose, arabinose, mannose, and glucose in the molar ratio of 1.0:0.6:0.4:0.2 was obtained by treatment of the whole polysaccharide extracted from red wine with cetrimide, followed by gel permeation chromatography. Spectroscopic and methylation analyses indicated that PS-SI is a mixture of neutral polysaccharides, consisting mainly of beta (1-->3)-linked galactopyranosyl residues, with side chains of galactopyranosyl residues at positions O-6. Arabinofuranosyl residues linked alpha (1-->5), alpha-mannopyranosyl and glucosyl residues appear to be components of different polysaccharides. The in vitro antioxidant capacity of fractions of wine polysaccharide was studied by hydroxyl radical scavenging and ORAC assays. Fraction PS-SI presented the strongest effect on hydroxyl radicals (IC(50)=0.21).
    Carbohydrate research 04/2009; 344(9):1095-101. DOI:10.1016/j.carres.2009.03.024 · 1.97 Impact Factor
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    ABSTRACT: A modified synthetic route for the complexes [Cu(II)5,7,12,14-tetramethyldinaphtho [b,i][1,4,8,11]tetraaza[14]annulene], [Cu(II)tmdnTAA], and [Cu(II) 5,7,12,14-tetramethyl-6,13-dichloro-dinaphtho[b,i][1,4,8,11]tetraaza[14]annulene], [Cu(II)dCltmdnTAA], is presented in this work. The electrochemical characterization of both complexes and their precursors, [bis(2,4-pentanedionato)copper(II)], [Cu(II)(acac)2] and [bis(3-chloro-2,4-pentanedionato)copper(II)], [Cu(II)(3-Cl-acac)2], respectively, under nitrogen and carbon dioxide is also presented. The voltammetric response of [Cu(II)(acac)2] and [Cu(II)(3-Cl-acac)2] are different compared to [Cu(II)tmdnTAA] and [Cu(II)dCltmdnTAA] under nitrogen. Precursors show the reduction of Cu(I) to Cu(0) and the tetraazadinaphtho[14]annulene complexes do not. The chlorine substituted complex has a lower reduction potential than the unsubstituted homologue under nitrogen atmosphere. However, the contrary response is obtained in the presence of carbon dioxide: the unsubstituted complex is more catalytic in terms of potential because the current discharge appears 270 mV shifted to the anodic region. These facts can be explained in terms of electronic and steric effects. The modified electrode obtained by oxidative electropolymerization of [Cu(II)tmdnTAA] over glassy carbon electrode presented a suitable amperometric response for the sulfite reduction in acidic medium (pH = 2.7). A linear correlation was observed for the catalytic current and sulfite concentration between 0.6–6.0 mM range.
    Journal of Coordination Chemistry 02/2008; 61(4-4):479-489. DOI:10.1080/00958970701370559 · 2.22 Impact Factor
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    ABSTRACT: Three glass electrodes covered with Co-cobaltite/SnO2:F (to obtain conducting glass electrodes) modified with p-Ni-tetraaminophenylporphyrin are described. In one electrode the porphyrin was absorbed on the electrode surface at room temperature, in another the porphyrin was electropolymerized on the electrode surface by cyclic voltammetry, and in the third the bare electrode was immersed in DMF containing the porphyrin and refluxed 6 h at 150°C. The three electrodes were tested as electrocatalysts for the oxidation of hydrazine and as potentiometric sensors of this chemical. The electrode modified by refluxing showed good electrocatalytic behavior as well as a linear relationship between its open circuit potential and the concentration of hydrazine in a concentration range from 0.16 to 12 µM, with fast response. These characteristics indicate that the conducting glass electrode of Co-cobaltite/SnO2:F covered with p-Ni-tetraaminophenylporphyrin by the reflux method is a good potentiometric sensor of hydrazine. The active site is probably the ligand that changes its electron density by formation of a supramolecular system.
    Journal of Coordination Chemistry 11/2007; 60(22-24-22):2499-2507. DOI:10.1080/00958970701275790 · 2.22 Impact Factor
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    ABSTRACT: 5,15-Bis(veratryl)porphyrin (1), 5,10,15-tris(veratryl)porphyrin (2), and 5,10,15,20-tetrakis(veratryl)porphyrin (3), C36H30N4O4, C44H38N4O6, and C52H46N4O8 were synthesized by an acid-catalyzed, one-pot reaction of meso-dipyrromethane, 3,4- di-OCH3-benzaldehyde (veratraldehyde), and trifluoroacetic acid (TFA). These three different products were obtained as a result of scrambling reactions. The molecular structures have been characterized by elemental analysis, ESI mass spectra, 1D and 2D NMR techniques (1H and 13C), and UV-visible spectroscopy.
    Synthetic Communications 11/2007; 37(12-12):2001-2009. DOI:10.1080/00397910701356496 · 0.98 Impact Factor
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    ABSTRACT: Reactions of photochemically or radiolytically generated radicals with tetrakis(x-aminophenyl)porphyrin, tapp2−, initiate the polymerization of the porphyrin complexes Mtapp, where M=Ni or Zn. In the photochemical process, the porphyrin-centered excited state of Mtapp reacts with the ground state to generate oxidized and reduced radical species. The cationic radical, M(tapp+), appears to be the initiator of the porphyrin polymerization. An electron transfer reaction between the excited state of Mtapp and a Co(III) complex generates also the cation radical and initiates the polymerization process. Pulse radiolytically generated Cl2- and OH radicals were also able to initiate the polymerization of the porphyrin complexes.
    Inorganica Chimica Acta 04/2006; 359(7):2281-2284. DOI:10.1016/j.ica.2005.08.036 · 2.04 Impact Factor
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    N4-Macrocyclic Metal Complexes, 01/2006: pages 191-254; Springer.
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    ABSTRACT: The electrochemical reduction of carbon dioxide was studied on a glassy carbon electrode modified with either polymeric M-tetrakis aminophthalocyanines (M = Co, Ni, Fe) or with the polymeric free ligand, in aqueous electrolyte. The reaction products are dependent on the central ion: for Co-polymer the only reaction product found was formic acid; for Ni polymer, formic acid and formaldehyde were found, whereas formaldehyde and H 2 were detected for Fe polymer. For the free ligand polymer only H 2 was detected. Spectroelectrochemical experiments show that in the case of Co-polymer, Co(I) is the active site of the electrocatalysis but the reduced cobalt center and the reduced ligand are not enough to promote the reduction of the carbon dioxide and an extra overpotential is necessary. In the case of the Ni polymer, the reaction takes place at the same potential where the complex is double reduced and it is not necessary to apply more potential. On the other hand, there are important differences between the morphologies of both polymers as demonstrated by electrochemical impedance spectroscopy. The experiments show that the metallic center affects the kinetics of polymerization and the polymer morphology. On the other hand, the chemical nature of the metal center of the catalyst is the most important factor in the electrochemical reduction of CO 2 and the products involved.
    Journal of Molecular Catalysis A Chemical 03/2005; 229(1-2). DOI:10.1016/j.molcata.2004.11.026 · 3.68 Impact Factor
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    ABSTRACT: Electrocatalytic carbon dioxide reduction was studied in aqueous media on glassy carbon electrode coated with polymeric Co-tetra-3-aminophenylporphyrin. The polymeric complex-modified electrode catalyses the carbon dioxide reduction to carbon monoxide and formic acid. The monomeric system does not catalyze the reduction probably because it is not stable. The polymer, instead, presents higher activity at lower potentials and loses its activity only after more than four hours of electrolysis at constant potential. The redox couple responsible for the catalysis is Co(II)/Co(I). Kinetic electro-reduction parameters for the polymer-modified electrode were obtained and a probable mechanism operating in aqueous media containing sodium perchlorate as electrolyte is proposed.
    Journal of the Chilean Chemical Society 06/2003; 48(2). DOI:10.4067/S0717-97072003000200016 · 0.47 Impact Factor
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    ABSTRACT: The electrocatalyzed reduction of carbon dioxide was investigated with cobalt(II), nickel(II) and copper(II) complexes of hexaaza-macrocycle ligands. The macrocyclic ligands were obtained via the condensation of phenanthroline or bipyridine. The X-ray structure of a triflate derivative was determined and it showed the less common “CuN4O2” centrosymmetric octahedral configuration with apically elongated CuO bonds. A preference for a neutral, mononuclear, octahedral configuration is exhibited by the planar macrocycle with an extended π-electron system. Its structure is characterized by shorter CuN bonds than those of Cu complexes with saturated macrocycles. The reduction of the complexes has been studied by cyclic voltammetry and UV–Vis spectroscopy. The results show that the metal center in its lower oxidation state, i.e. M(I), is the active site. The metal center is oxidized to M(II) in the presence of CO2 with the concomitant formation of an adduct between the metal center and CO2. A further one electron reduction regenerates the catalyst and produces carbon monoxide and/or formic acid. A theoretical model is proposed for a simple mechanism that involves initial coordination of CO2 to the metal center.
    Inorganica Chimica Acta 11/2002; 339:224–232. DOI:10.1016/S0020-1693(02)00942-8 · 2.04 Impact Factor
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    ABSTRACT: Electrocatalytic hydrazine oxidation was studied by using a glassy carbon electrode coated with monomeric and polymeric Fe-tetraaminophthalocyanine. The polymeric complex-modified electrode is a better catalyst than the monomer-modified electrode. It presents higher activity at lower potentials and a very good reproducibility. A linear correlation between Ip and hydrazine concentration in a wide range, from 1×10−6 to 1×10−2M at pH 13 for the polymer-modified electrode was obtained. The open circuit measurements for the polymer-modified electrode in aqueous solution in both presence and absence of hydrazine show that an electronic transfer occurs without an applied potential, from the hydrazine to the Fe (II) metal center. The kinetic electro-oxidation parameters for the polymer-modified electrode were investigated and a probable mechanism operating at pH 13 is proposed.
    Journal of Molecular Catalysis A Chemical 01/2001; 165(1):169-175. DOI:10.1016/S1381-1169(00)00411-8 · 3.68 Impact Factor
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    ABSTRACT: Recent literature results on inorganic models related to metalloenzymes which transport electrons or activate small molecules are discussed in this review. The molecular systems are essentially restricted to macrocyclic or polydentate ligands preferentially containing nitrogen atoms and pendant arms. The discussion is mainly concerned with aspects such as spectroscopic, electrochemical and chemical characterization of the systems and electro- or photo-activation of small molecules.
    Coordination Chemistry Reviews 03/2000; 196(1-196):125-164. DOI:10.1016/S0010-8545(99)00165-4 · 12.10 Impact Factor
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    ABSTRACT: In this paper we present a theoretical model to determine interaction energies from the profiles of electronic global properties such as chemical potential and hardness. The procedure is based upon already established relationships among these properties and is applied to the qualitative analysis of the reduction mechanism of oxygen by the iron tetraazaporphyrin (FeTAP). As a result, the interaction is qualitatively rationalized in terms of a [physisorption]→[chemisorption] process where at O2⋯FeTAP distances larger than 1.9 Å the oxygen is physisorbed and the adduct is characterized by weak intermolecular interactions. For distances smaller than 1.9 Å, the oxygen is chemisorbed, and the adduct is characterized by a complex with a formal Fe–O bond. The adduct structures generated from these mechanisms are separated by a potential barrier of about 6 kJ/mol.
    Journal of Molecular Structure THEOCHEM 07/1999; 493:219-224. DOI:10.1016/S0166-1280(99)00242-0 · 1.37 Impact Factor
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    ABSTRACT: Cobalt phthalocyanine (CoPc) and cobalt naphthalocyanine (CoNPc) exhibit different redox and electronic properties. Redox processes on CoPc are more reversible than on CoNPc. The pH dependence of those processes is also different for these complexes, which could indicate that in the case of CoNPc, the redox couples observed involve the macrocyclic ligand and not the metal as with CoPc. This seems to explain the different redox properties and kinetics for O2 reduction and N2H4 oxidation of these two macrocyclics. In this study we compare the electrocatalytic activity of these two phthalocyanines, adsorbed on glassy carbon, for the electrochemical reduction of O2 and for the oxidation of hydrazine.
    Electrochimica Acta 05/1998; 43(12-13):1821-1827. DOI:10.1016/S0013-4686(97)00314-9 · 4.50 Impact Factor

Publication Stats

325 Citations
62.82 Total Impact Points

Institutions

  • 1994–2014
    • University of Santiago, Chile
      • • Departamento de Química de los Materiales
      • • Facultad de Química y Biología
      • • Facultad de Ciencia
      CiudadSantiago, Santiago Metropolitan, Chile
  • 1992
    • Universidade Federal de São Carlos
      • Departamento de Química (DQ)
      São Carlos, Estado de Sao Paulo, Brazil