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Journal ArticleDOI

Electrochemical behaviour of 2-nitrobenzidine in N,N-dimethylformamide

TL;DR: In this paper, the electrochemical reduction of 2-nitrobenzidine (I) has been investigated in N,N-dimethylformamide solutions and two well-defined polarographic waves in the ratio 1:3 were obtained.
About: This article is published in Journal of Electroanalytical Chemistry.The article was published on 1984-08-10. It has received 12 citations till now. The article focuses on the topics: Cyclic voltammetry & Nitroso.
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Journal ArticleDOI
TL;DR: In this paper, the status of research on the dynamics of electrochemical reactions is reviewed, including the electrodissolution of metals, cathodic deposition, and electrocatalytic reactions.

323 citations

Journal ArticleDOI
TL;DR: In this paper, a systematic and comprehensive study on cyclic voltammetric anodic current oscillation (CVACO) at a hanging mercury drop electrode (HMDE) was carried out for the redox reactions of molecular oxygen (O2), nitrobenzene (NB), 1,4-dinitrobenzaene (DNB), benzoquinone (BQ), 2,3,5,6-tetramethylbenzoquinones (TMBQ), benzophenone (BP), azobenzene (AB), 2
Abstract: A systematic and comprehensive study on cyclic voltammetric anodic current oscillation (CVACO) at a hanging mercury drop electrode (HMDE) was carried out for the redox reactions of molecular oxygen (O2), nitrobenzene (NB), 1,4-dinitrobenzene (DNB), benzoquinone (BQ), 2,3,5,6-tetramethylbenzoquinone (TMBQ), benzophenone (BP), azobenzene (AB), 2,1,3-benzothiadiazole (BTD), 7,7,8,8-tetracyanoquinodimethane (TCNQ), methyl viologen dichloride (MV2+), and tris(2,2‘-bipyridine)ruthenium(II) dichloride [Ru(bpy)32+] in dimethyl sulfoxide (DMSO) solutions containing 0.1 M tetraethylammonium perchlorate (TEAP). From the electrocapillary curve (ECC) obtained using a dropping mercury electrode as well as the capacitance versus potential curves measured using electrochemical impedance technique, the value of the potential of zero charge (PZC) was estimated to be −0.27 V versus Ag|AgCl|NaCl (sat.) in a DMSO solution containing 0.1 M TEAP. CVACO was found to occur only for the redox couples (i.e., BP0/BP•-, O20/O2•-, AB0...

26 citations

Journal ArticleDOI
TL;DR: In this article, the authors observed the redox reaction of the O 2 /O 2 − (superoxide ion) couple on a hanging mercury drop electrode (HMDE) in a limited aprotic medium.

18 citations

Journal ArticleDOI
TL;DR: The polarographic streaming maxima and cyclic voltammetric anodic current oscillation (CVACO) at a hanging mercury drop electrode (HMDE) in room-temperature ionic liquid (RTIL) have been studied for the first time using cyclic CVACO, potential step chronoamperometric and pulse voltametric techniques.
Abstract: The polarographic streaming maxima and cyclic voltammetric anodic current oscillation (CVACO) at a hanging mercury drop electrode (HMDE) in room-temperature ionic liquid (RTIL) have been studied for the first time using cyclic voltammetric, potential step chronoamperometric and pulse voltammetric techniques. The reversible redox reaction of the 2,1,3-benzothiadiazole (BTD)/BTD•- (an anion radical of BTD) couple with a formal potential (E0‘) of −1.36 V versus Ag/AgCl/NaCl(saturated) in 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4) RTIL was typically employed for this purpose. A maximum was observed at the rising part of the normal pulse voltammogram for the reduction of BTD to BTD•- as well as of the reversed pulse voltammogram for the reoxidation of BTD•- to BTD at the HMDE. The conditions of the initiation and control of the CVACO at the HMDE in EMIBF4 were extensively investigated. Generally, the CVACO was enhanced by increasing the concentration of BTD at a given potential scan rate (υ) and wa...

17 citations

Journal ArticleDOI
TL;DR: In this article, the movement of the mercury surface and the streaming of solution that accompany the current oscillation in the redox reaction of the O 2 /O 2 - (superoxide ion) couple on a hanging mercury drop electrode (HMDE) have been investigated using a combined system of two laser interferometric techniques.
Abstract: The movement of the mercury electrode surface and the streaming of solution that accompany the current oscillation in the redox reaction of the O 2 /O 2 - (superoxide ion) couple on a hanging mercury drop electrode (HMDE) have been investigated using a combined system of two laser interferometric techniques. That is, the simultaneous observation of both of these phenomena could be carried out. The movement of the mercury electrode surface during the oscillation was observed by the Michelson interferometric technique, and at the same time, the streaming of solution around the electrode was done by the Mach-Zehnder interferometric technique. These observations confirm that the electrochemical oscillatory phenomena of the O 2 /O 2 - redox couple are caused by the streaming phenomena, that is, the movement of a mercury electrode surface and adjoining solution resulting from an inhomogeneous polarization of the electrode.

12 citations

References
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TL;DR: In this paper, the integral equations obtained from the boundary value problems were solved and extensive data were calculated which permit construction of stationary electrode polarograms from theory, making it possible to develop diagnostic criteria so that unknown systems can be characterized by studying the variation of peak current, half-peak potential, or ratio of anodic to cathodic peak currents as a function of rate of voltage scan.
Abstract: was developed for solving the integral equations obtained from the boundary value problems, and extensive data were calculated which permit construction of stationary electrode polarograms from theory. Correlations of kinetic and experimental parameters made it possible to develop diagnostic criteria so that unknown systems can be characterized by studying the variation of peak current, half-peak potential, or ratio of anodic to cathodic peak currents as a function of rate of voltage scan.

4,542 citations

Journal ArticleDOI
TL;DR: Chandross, Longworth, and Viscoz as discussed by the authors showed that the emission spectrum comprises two or more components, the spectral distribution of the component shortest in wavelength is similar to that of anthracene fluorescence, but the others are broad, structureless, and located toward the red with respect to the first component.
Abstract: The electrogenerated chemiluminescence (ECL) of anthracene is characterized by emission at the frequency of anthracene fluorescence and also at longer wavelengths. One longer wavelength component is shown to be caused by emission from anthranol produced by decomposition of the cation radical of anthracene and prbbably excited by energy transfer from excited anthracene. Another component, arising from ECL of anthranol itself, is also observed. revious reports of electrogenerated chemiluminescence (ECL) from anthracene solutions in N,Ndimethylformamide (DMF) have noted that the emission spectrum comprises two or more components. The spectral distribution of the component shortest in wavelength is similar to that of anthracene fluorescence, but the others are broad, structureless, and located toward the red with respect to the first component.2s3 This general behavior is common among several polycyclic hydrocarbons and their derivatives. Presently four alternatives are available to explain the longwavelength emission from these systems. Chandross, Longworth, and Viscoz have proposed the formation of an anthracene excited state dimer (excimer), which radiates to produce the low energy emission. A similar explanation is the formation of an anthracene excited state complex with some other species (exciplex). Both the excimer and the exciplex dissociate into component ground state molecules upon deactivation. Zweig, Maricle, Brinen, and Maurer have suggested that solution phosphorescence may be responsible for the longwavelength emission in some of these systems4 Finally, wes have previously pointed out the possibility of emission from an excited state of a product formed during the reaction of the electrogenerated radical ions with their environment. Anthracene has been chosen for study because it is representative of the class of hydrocarbons exhibiting this behavior and because it is available and easily purified. We have performed a number of experiments designed to aid in identifying the emitting species in the anthracene-DMF system, and to help illuminate the means of exciting the species in so lu t ion which do emit. Experimental Section The anthracene used in all experiments was produced by Matheson Coleman and Bell (mp 215-217”). It was purified by triple recrystallization from Baker Spectroquality benzene and Baker Reagent Grade methanol according to a modification of a procedure available in the l i terat~re .~ A portion of the triply recrystallized (1) (a) National Science Fcundation Predoctoral Fellow; (b) to whom correspondence and requests for reprints should be directed. (2) E. A. Chandross, J. W. Longworth, and R. E. Visco, J . A m . Chem. Soc., 87, 3259 (1965). (3 ) A . J. Bard, I<. S . V. Santhanam, S . A. Cruser, and L. R. Faulkner in “Fluorescence,” G. G. Guilbault, Ed., Marcel Dekker, Inc., New York, N. Y . , 1967, Chapter 14. (4) A. Zweig, D. L. Maricle, J. S . Brinen, and A. H. Maurer, J . Am. Chem. Soc., 89, 473 (1967). material was also resublimed twice in DCICUO. No differences in behavior .were found between the material which had been doubly resublimed after recrystallization and that which had merely been recrystallized thrice. For this reason, most subsequent experiments used only the triply recrystallized anthracene. Fluorescence analysis of cyclohexane solutions of the purified anthracene showed no luminescence bands other than those directly attributable to anthracene.6 Maxima in fluorescence intensity were found at 378, 397, 420, 447, and ca. 475 mp. In particular tetracene was shown by absorption spectroscopy and by fluorescence measurements to be present in amounts less than 0.1 z, since none was detectable by these methods. The solvent used in every case was N,N-dimethylformamide which was also supplied by Matheson Coleman and Bell (bp 152154”). The solvent was further purified,by two methods. Method A involved storing the solvent over anhydrous cupric sulfate for several days to complex water and dimethylamine. The solvent was then decanted and distilled at a reflux ratio of 5 from a glass bead packed column 100 cm high under a nitrogen pressure of 20 mm. The middle fraction was retained for use. Method B also involved storage over anhydrous cupric sulfate For a period of several days. The distillation which followed was under the same conditions as above except that the reflux ratio was unity. Following this distillation, the solvent was stored over Linde Type 4A Molecular Sieves for a period of 48 hr. Then the material was decanted and redistilled using a reflux ratio of .l. Once again, only the middle fraction rvas taken. The solvent was stored under an inert helium atmosphere. Neither solvent batch showed fluorescence bands, even under the most sensitive conditiuris. The supporting electrolyte used in all experiments was tetra-rzbutylammonium perchlorate (TBAP), Polarographic grade, supplied by Southwestern Analytical Chemicals, Austin, Texas. The TBAP was used without further purification, but was dried in a vacuum oven for 48 hr at a temperature of 100” and then stored in a desiccator over magnesium perchlorate. The TBAP contained no fluorescent impurities. The electrolysis cell used for ECL emission measurements consisted of two platinum helices inserted through graded seals into the Pyrex wall of a 14/35 standard taper joint, as shown in Figure 1. An adapter was provided so that the cell could be evacuated easily. The electrodes were 2-5 mm apart. It was generally found that greatest emission intensities were incident upon the monochromator entrance slits when the slits and the two electrodes were arranged colinearly. This arrangement was used uniformly in the experiments. Immediately after loading the cell, it was degassed on a vacuum line similar to that described previously7 using two freeze-pumpthaw cycles. Minimum pressure over the frozen solution on the second cycle was at most 10-4 torr in every case. The voltage applied to the cell was simply the 60-cycle sinusoidally alternating line voltage which was reduced from 110 V root mean square to any (5) T. Takeuchi and M . Furusawa, Kogpo Kagaku Zasshi, 68, 474 ( 6 ) I. Berlman, “Handbook of Fluorescence Spectra of Organic (7) K. S. V. Santhanam and A. J. Bard, J . A m . Chem. Soc., 88, 2669 (1965); Chem. Abstr., 63, 4060e (1965). Molecules,” Academic Press, New York, N . Y., 1965.

88 citations

Journal ArticleDOI
TL;DR: In this article, Elektronengasmodelle of Farbstoffen (Cyanine, Polyene, Polyacetylene, Acridine, Xanthene, Oxazine, Azine, Bacteriochlorophyll, Phthalocyanin, Azulen) are beschrieben.
Abstract: Die Farbe organischer Verbindungen hangt von strukturellen Einzelheiten des Molekuls ab. Es werden Elektronengasmodelle von Farbstoffen (Cyanine, Polyene, Polyacetylene, Acridine, Xanthene, Oxazine, Azine, Bacteriochlorophyll, Phthalocyanin, Azulen) beschrieben. Die Zustande von π-Elektronen werden durch eindimensionale Elektronenwellen entlang der Molekulkette (eindimensionales Modell) bzw. durch Wellenfunktionen, die sich uber die Molekulebene erstrecken, (zweidimensionales Modell) dargestellt. Energiewerte und Wellenfunktionen der Elektronen lassen sich mit Hilfe eines neu entwickelten Analogrechners ermitteln, und daraus konnen Lage, Starke und Form der Absorptionsbanden berechnet werden. Beide Modelle zeigen, das z. B. in langkettigen Polyenen ein ebenso ausgepragter Unterschied zwischen alternierend auftretenden langen und kurzen Bindungen vorhanden ist wie im Butadien.

73 citations

Journal ArticleDOI
TL;DR: In this paper, the half-wave potential for the reduction of DPA to DPA was shown to be equal to that calculated by molecular orbital theory, using an angle between the 9 and 10-phenyl groups and the anthracene nucleus based on electron spin resonance measurements.
Abstract: The electroreduction of 9,lO-diphenylanthracene (DPA) in dimethylformamide solutions was studied by polarography, cyclic voltammetry, chronopotentiometry, and coulometry. The results generally confirmed the mechanism proposed for the reduction of aromatic hydrocarbons based on polarographic experiments. Coulometric experiments demonstrated that with sufficient care in solution preparation 1 Faraday per mole of DPA was consumed and fairly stable solutions of DPAcould be obtained. The protonation of DPAby hydroquinone was also studied. The half-wave potential for the reduction of DPA to DPAwas shown to be equal to that calculated by molecular orbital theory, using an angle between the 9and 10-phenyl groups and the anthracene nucleus based on electron spin resonance measurements. An explanation of the pronounced streaming which occurs at mercury electrodes during oxidation of DPAis given. he electrochemistry of aromatic hydrocarbons in T aprotic solvents has been the subject of a number of studies. These investigations are of interest because the radical ions which are formed at the electrode may undergo further chemical or electrode reactions. Further interest lies in the correlation between the polarographic half-wave potentials for the reduction of the hydrocarbon (R) to its radical anion (R-.) with electron affinities, ultraviolet absorption frequencies, or parameters calculated by molecular orbital (MO) theory.*r3 Although the results of dc and ac polarography fit very well with assumed mechanisms and the known chemistry of aromatic hydrocarbons (e.g., reduction with alkali metals), very few studies have been made using some of the more recent electrochemical techniques such as cyclic voltammetry and chronopotentiometry. Neither have electrochemical studies been made of the radical anions themselves. Furthermore, the coulometric reduction of these compounds at the first reduction plateau gave evidence of a twoelectron r e d ~ c t i o n , ~ which was ascribed to the reaction of Rwith the solvent (dimethylformamide) producing R H . , which was reduced in a second one-electron step at these potentials. This finding seemed at variance with the known stability of R , as observed through optical and electron spin resonance (esr) studies. Finally, although theoretical considerations lead to the predication that the protonated radical (RH. ) should reduce at less cathodic potentials than R, no direct attempts have been made to obtain R H and study its electrochemistry. The aim of this investigation was to study the electrochemical reduction of an aromatic hydrocarbon by a variety of electrochemical techniques, in order to confirm and extend the previously described mechanisms. The choice of 9,lO-diphenylanthracene (DPA) was based on interest in this substance in chemiluminescence experiment^.^ Furthermore, a comparison of elec(1) To whom correspondence and request for reprints should be directed. (2) This work has been reviewed in (a) G. J. Hoijtink, Ric. Sci., Suppl., 30, 217 (1960); (b) G. J. Hoijtink, Rec. Trav. Chim., 76, 885 (1957); (c) M. E. Peover in “Electroanalytical Chemistry. A Series of Monographs on Recent Advances,” Vol. 11, A. J. Bard, Ed., Marcel Dekker, Inc., New York, N. Y., in preparation. (3) (a) A. Maccol, Nafure, 163, 178 (1949); (b) F. A. Matsen, J. Chem. Phys., 24, 602 (1956); (c) G. J. Hoijtink, Rec. Trau. Chim., 74, 1525 (1955). (4) D. E. G. Austen, P. H. Given, D. J. E. Ingram, and M. E. Peover, Nature, 182, 1784 (1958). trochemical and esr parameters with those calculated by MO theory can provide information about the extent of nonplanarity of DPA. The electrochemical reduction of DPA and oxidation of DPAin the absence of proton donors will be described first. Then the effect of proton donors will be discussed. Finally a correlation of the observed halfwave potentials and those predicted by MO theory will be given and an explanation of the stirring effect which occurs during the electrooxidation of anion radicals will be presented.

61 citations