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Stevic M.C.,University of Belgrade | Ciric-Marjanovic G.,University of Belgrade | Marjanovic B.,Centrohem | Ignjatovic L.M.,University of Belgrade | Manojlovic D.,University of Belgrade
Journal of the Electrochemical Society | Year: 2012

The theoretical study of the 6-aminoquinoline (6-QNH2) electrochemical oxidationmechanism, based on the semi-empirical quantum chemical computations of the heat of formation, ionization energy, and spin density of reaction intermediates, taking into account the influence of pH and solvation effects, has been conducted. Two possible 6-QNH2 electro-oxidation pathways are investigated, namely, the initial single-electron oxidation of 6-QNH2 at lower electrode potentials, leading to the formation of cation radicals [6-QNH2]• in acidic solutions and neutral radicals [6-QNH]• in alkaline solutions, as well as the two-electron oxidation of 6-QNH2 leading to the initial formation of nitrenium cations [6-QNH]+ at higher electrode potentials. The regioselectivity of 6-QNH2 dimerization reactions, which follow both the single- and two-electron transfer reactions, is computationally studied. Cyclic voltammetry experiments, conducted at a glassy carbon paste electrode in Britton-Robinson buffer/methanol media, are correlated with the computationally predicted 6-QNH2 electro-oxidation mechanism. Differential pulse voltammetric and adsorptive stripping differential pulse voltammetric analyses of 6-QNH2 oxidation have also been performed. Copyright © 2012 The Electrochemical Society.


Marjanovic B.,Centrohem | Juranic I.,University of Belgrade | Ciric-Marjanovic G.,University of Belgrade
Journal of Physical Chemistry A | Year: 2011

New computational insights into the mechanism of the Boyland-Sims oxidation of arylamines with peroxydisulfate (S 2O 8 2?) in an alkaline aqueous solution are presented. The key role of arylnitrenium cations, in the case of primary and secondary arylamines, and arylamine dications and immonium cations, in the case of tertiary arylamines, in the formation of corresponding o-aminoaryl sulfates, as prevalent soluble products, and oligoarylamines, as prevalent insoluble products, is proposed on the basis of the AM1 and RM1 computational study of the Boyland?Sims oxidation of aniline, ring-substituted (2-methylaniline, 3-methylaniline, 4-methylaniline, 2,6-dimethylaniline, anthranilic acid, 4-aminobenzoic acid, sulfanilic acid, sulfanilamide, 4-phenylaniline, 4-bromoaniline, 3-chloroaniline, and 2-nitroaniline) and N-substituted anilines (N-methylaniline, diphenylamine, and N,N-dimethylaniline). Arylnitrenium cations and sulfate anions (SO 4 2?) are generated by rate-determining two-electron oxidation of primary and secondary arylamines with S 2O 8 2?, while arylamine dications/immonium cations and SO 4 2? are initially formed by two-electron oxidation of tertiary arylamines with S 2O 8 2?. The subsequent regioselectivity-determining reaction of arylnitrenium cations/arylamine dications/immonium cations and SO 4 2?, within the solvent cage, is computationally found to lead to the prevalent formation of o-aminoaryl sulfates. The formation of insoluble precipitates during the Boyland?Sims oxidation of arylamines was also computationally studied. © 2011 American Chemical Society.


Janosevic A.,University of Belgrade | Marjanovic B.,Centrohem | Rakic A.,University of Belgrade | Ciric-Marjanovic G.,University of Belgrade
Journal of the Serbian Chemical Society | Year: 2013

Recent advances in synthesis, characterization and application of the selected conducting/semiconducting and redox-active oligomers and polymers of arylamines are reviewed. A brief historical background of the selected topics is given. The overview of the preparation, structure and properties of polyaniline, substituted polyanilines, especially those obtained by the oxidative polymerization of p-substituted anilines, poly(1-aminonaphthalene) and its derivatives, carbocyclic and heterocyclic polyaryldiamines such as poly(p-phenylenediamine) and polydiaminoacridines, is presented. The mechanism of formation of polyaniline nanostructures is discussed. Recent approaches to the preparation of one-dimensional polyaniline nanostructures are concisely reviewed, with special attention paid to the template-free falling-pH method. Current and potential future applications of oligo/polyarylamines are briefly discussed. ©2013 SCS.


Marjanovic B.,Centrohem | Juranic I.,University of Belgrade | Ciric-Marjanovic G.,University of Belgrade | Pasti I.,University of Belgrade | And 2 more authors.
Reactive and Functional Polymers | Year: 2011

Novel electroactive paramagnetic ortho-coupled aniline oligomers functionalized with ethyl ester groups were synthesized by the oxidation of the 4-carbethoxyaniline, well known anesthetic benzocaine, with ammonium peroxydisulfate in an acidic aqueous medium at room temperature. Oligobenzocaines were characterized by elemental analysis, gel-permeation chromatography, conductivity measurements, FTIR, Raman and EPR spectroscopies, and scanning electron microscopy. Theoretical study of the mechanism of benzocaine oxidation has been based on the AM1 and RM1 semi-empirical quantum chemical computations of the heat of formation and ionization energy of the benzocaine, protonated benzocaine, generated reactive species and reaction intermediates, taking into account influence of pH and solvation effects. Electroactivity of the oligobenzocaines was studied by the cyclic voltammetry. © 2011 Elsevier Ltd. All rights reserved.


Stevic M.C.,University of Belgrade | Ignjatovic L.M.,University of Belgrade | Ciric-Marjanovic G.,University of Belgrade | Marjanovic B.,Centrohem | And 2 more authors.
Journal of Electroanalytical Chemistry | Year: 2012

Experimental study of the electro-oxidation behavior of 6-hydroxyquinoline (6HQ) has been performed using cyclic voltammetry (CV) on a glassy carbon paste electrode (GCPE). The theoretical study of the 6HQ electrochemical oxidation mechanism, based on the AM1 semi-empirical quantum chemical computations of the heats of formation and ionization energy of reaction intermediates, taking into account influence of pH and solvation effects, has also been conducted. It was established that a two-electron, irreversible process, controlled by diffusion of electroactive species, is responsible for an oxidation peak of 6HQ that appears in all cyclic voltammograms recorded on a clean electrode, in solutions of pH range 2-12, with a supporting electrolyte of Britton-Robinson buffer/methanol. A single-electron oxidation of 6HQ leads, depending on pH, to the formation of various free radical species that combine to make C5-C5 coupled 6HQ dimers which, after being oxidized once more, give quinonoid-type compounds. The irreversible electrochemical oxidation of 6HQ does not stop after the dimerization step but proceeds further to the formation of oligo/poly(6HQ). The optimum conditions for Differential Pulse Voltammetry (DPV) determinations were established and it was shown that for more sensitive quantitative determinations Adsorptive Stripping Differential Pulse Voltammetry (AdSDPV) can be used. © 2012 Elsevier B.V. All rights reserved.


Rakic A.,University of Belgrade | Bajuk-Bogdanovic D.,University of Belgrade | Mojovic M.,University of Belgrade | Ciric-Marjanovic G.,University of Belgrade | And 5 more authors.
Materials Chemistry and Physics | Year: 2011

The oxidation of aniline with ammonium peroxydisulfate in water without added acid was studied in dilute reaction media. The new nanostructured nonconducting polyaniline sulfate/hydrogen sulfate, synthesized by dilute dopant-free template-free falling-pH method, consists of network of nanorods and nanogranules. The molecular structure of polyaniline, investigated by the elemental analysis, FTIR, Raman, UV-Vis and EPR spectroscopies, was found to be significantly different in comparison with the structure of the nanostructured PANI sulfate/hydrogen sulfate prepared by dopant-free template-free falling-pH method in concentrated aqueous aniline solutions. The mechanism of the formation of nanostructured polyaniline under dopant-free template-free dilute reaction conditions is discussed. © 2011 Elsevier B.V. All rights reserved.


Marjanovic B.,Centrohem | Juranic I.,University of Belgrade | Mentus S.,University of Belgrade | Ciric-Marjanovic G.,University of Belgrade | Holler P.,Czech Institute of Macromolecular Chemical
Chemical Papers | Year: 2010

Anilinium 5-sulfosalicylate was prepared and characterized by elemental analysis, and FTIR and NMR spectroscopies. It was polymerized in an aqueous solution using ammonium peroxydisulfate as an oxidant. The precipitated polyaniline 5-sulfosalicylate exhibited high thermal stability and conductivity of 0.13 S cm-1. Its mass-average molar mass and polydispersity index were determined by gel-permeation chromatography as 22,900 g mol-1 and 2.7, respectively. Elemental analysis and FTIR spectroscopy study of polyaniline 5-sulfosalicylate revealed the doping level and the oxidation state between emeraldine and protoemeraldine salt while corresponding studies of the polyaniline base indicate a small extent of the covalent bonding of 5-sulfosalicylate anions to polyaniline chains. © 2010 Institute of Chemistry, Slovak Academy of Sciences.


Janosevic A.,University of Belgrade | Ciric-Marjanovic G.,University of Belgrade | Marjanovic B.,Centrohem | Trchova M.,Czech Institute of Macromolecular Chemical | Stejskal J.,Czech Institute of Macromolecular Chemical
Materials Letters | Year: 2010

Self-assembled polyaniline nanorods were synthesized by the oxidation of aniline with ammonium peroxydisulfate in an aqueous solution in the presence of 3,5-dinitrosalicylic acid, using the template-free falling-pH method. The effects of the mole ratio of 3,5-dinitrosalicylic acid to aniline, i.e., of starting pH, monomer concentration, and reaction time on the yield of polymerization, molecular-weight distribution, molecular structure, morphology, and conductivity of the prepared polyanilines have been studied by gel-permeation chromatography, elemental analysis, FTIR and Raman spectroscopies, scanning and transmission electron microscopies, and conductivity measurements. The weight-average molecular weights and polydispersity index were in the range 36,400-54,900 and 3.7-7.6, respectively. Synthesized polyaniline nanorods have a diameter of 25-280 nm and a length of 0.2-1.3 μm, and conductivities in the range (1.2-4.6) × 10-2 S cm-1. The formation mechanism of self-assembled polyaniline nanorods has been discussed. © 2010 Elsevier B.V.


Janosevic A.,University of Belgrade | Ciric-Marjanovic G.,University of Belgrade | Sljukic Paunkovic B.,University of Belgrade | Pasti I.,University of Belgrade | And 3 more authors.
Synthetic Metals | Year: 2012

The oxidation of aniline with ammonium peroxydisulfate (APS) in aqueous solution of the plant-derived polyphenol, tannic acid, is reported. The effect of initial mole ratios [tannic acid]/[aniline] and [APS]/[aniline] on molecular structure, morphology, conductivity, and electroactivity of synthesized materials (PANI-TA) was investigated by UV-Vis, FTIR, Raman and EPR spectroscopies, scanning and transmission electron microscopies (SEM and TEM), conductivity measurements, and cyclic voltammetry, respectively. PANI-TA nanorods with the average diameter of 70-100 nm and conductivity of 1 × 10-3 S cm-1 were synthesized at [tannic acid]/[aniline] = 0.01 and [APS]/[aniline] = 1, while nonconductive, solid microspheres were obtained at [tannic acid]/[aniline] = 0.1 and [APS]/[aniline] = 2. The mechanism of the early stages of simultaneous oxidation of aniline and tannic acid has been computationally studied by the RM1/COSMO method. © 2012 Elsevier B.V. All rights reserved.


Ciric-Marjanovic G.,University of Belgrade | Marjanovic B.,Centrohem | Bober P.,Czech Institute of Macromolecular Chemical | Rozlivkova Z.,Czech Institute of Macromolecular Chemical | And 3 more authors.
Journal of Polymer Science, Part A: Polymer Chemistry | Year: 2011

The oxidative polymerization of p-phenylenediamine with silver nitrate by using various oxidant/monomer mole ratios in aqueous solutions of both acetic and nitric acid was studied experimentally and computationally. The produced micro/nanostructured conducting poly(p-phenylenediamine)-silver composites, reaching the conductivities >104 S/cm, were characterized by conductivity and density measurements, gel permeation chromatography, transmission electron microscopy, UV-visible, FTIR, and Raman spectroscopies. The highest conductivity was 31,700 S/cm for poly(p-phenylenediamine) base-silver (81.4 wt % Ag). The unexpected increase of conductivity after deprotonation of polymer component is discussed on the basis of interfacial electrical barriers and their removal. Theoretical study of the mechanism of p-phenylenediamine oxidation has been based on the AM1 semi-empirical quantum chemical computations of the heat of formation of the reaction intermediates, taking into account the influence of pH and solvation effects. Quantum chemical predictions of molecular structure of poly(p-phenylenediamine) were correlated with spectroscopic findings. © 2011 Wiley Periodicals, Inc.

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