REDOX PROCESSES IN THE REACTIONS OF N-ARYLSULFONYL-1,4-NAPHTНOQUINONЕIMINES WITH CERTAIN NUCLEOPHILES

Quinone-hydroquinone pairs are prototypes of organic redox systems, and studies of the electrochemical behavior of these compounds are of great interest for research. Electrochemical behavior associated with the equilibrium of electron-proton transfer provides information about the molecular structure and environment of the process. Apart from chemical aspects, quinones play an important role in the biochemistry of living cells. Quinone derivatives, used as drugs for several types of human cancers, have been found to have their biological activity related to their redox behavior. Quinoneimines-aminophenols form similar pairs. In nucleophilic addition reactions of N‑substituted p-quinoneimines, parallel redox processes are often observed, and the higher the redox potential of quinoneimine, the greater the likelihood of such processes. Naphthoquinoneimines with aromatic amines and acylhydrazines follow the scheme of 1,4-addition, but as reaction products are oxidized products -4-arylsulfonylamido‑2-arylamino(2-aroylamino)-1,4-naphthoquinoneimines. The oxidant may be the original naphthoquinoneimine and oxygen. Studies have shown that oxygen in the reaction of 1,4-naphthoquinoneimines with acylhydrazines is the only oxidant that oxidizes the product of 1,4-addition, as evidenced by the study of redox potentials. Both oxidized and reduced form of the compounds, as naphthoquinoneimine and the corresponding aminonaphthol, are used to determine the redox potential by direct potentiometry. Due to the instability of the reduced form in the case of the pair naphthoquinoneimine-aminonaphthol, we used only the reduced form, which is oxidized in the cell by oxygen. The redox potential of the naphthoquinoneimine-aminonaphthol galvanic pair was determined as the average value between the potential Emax, which was established in the system upon complete oxidation of the starting substance, that is, when only naphthoquinone imine remains in the system, and the potential Emin, which was registered at the beginning of the process in the system with the reduced form – the corresponding aminonaphthol. This is the method of direct potentiometry in the variant of the middle potential.

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Electrochemical reversibility of Me6Fc/Me6Fc+PF6- and Me8Fc/Me8Fc+PF6- redox systems in acetonitrile

Journal of Electrochemical Science and Engineering ◽

10.5599/jese.1032 ◽

2021 ◽

Author(s):

Nigar Z. Ibrahimova ◽

Gazanfar M. Jafarov ◽

Dilgam B. Tagiyev ◽

Iltifat U. Lyatifov

Keyword(s):

Redox Potential ◽

Methyl Groups ◽

Cyclic Voltammograms ◽

Redox Potentials ◽

Redox Systems ◽

Internal Reference ◽

Donor Property ◽

Optimal Position ◽

Electrochemical Reversibility ◽

Scan Rate

Two new redox systems, sym. 1,2,4,1¢,2¢,4¢-hexamethylferrocene/cation sym. 1,2,4,1¢,2¢,4¢-hexamethyl ferricinium and sym. octamethylferrocene/cation sym. Octamethylferricinium (MenFc/MenFc+, n = 6, 8) were studied by the cyclic voltammetry method. The observed difference between potentials of anodic and cathodic peaks of 0.063 to 0.075 V, and its independence on the potential scan rate, the straight-line dependence of the current value of anodic (and cathodic) peak on square root of the potential scan rate, as well as shapes of the recorded cyclic voltammograms indicate that both redox systems in acetonitrile meet the most important requirement of IUPAC regarding internal reference redox systems (IRRS) - electrochemical reversibility of electron transfer reaction. The same method under identical conditions was used to study the effect of the number of methyl groups on the redox potential of MenFc/MenFc+ systems, n = 0, 6, 8, 10. It was shown that the successive displacement of half-wave potential in the series of Fc/Fc+ - Me6Fc/Me6Fc+ - Me8Fc/Me8Fc+ -Me10Fc/Me10Fc+ towards negative potentials is attributed to the electron-donor property of methyl groups. The location of the redox potentials values of new systems [n=6 (111 mV), n=8 (23 mV)] between redox potentials of systems of n = 0 (431 mV) and n = 10 (-77 mV) means that the redox potential of the systems of MenFc/MenFc+(n = 6, 8) has an optimal position on the electrode potential scale, i.e. meets another of the IUPAC criteria for IRRS.

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Electroréduction de dérivés dinitrés aromatiques. V. influences du matériau d'électrode et de systèmes rédox sur les réductions du 4,4′-dinitrodibenzyle et de l'acide 4,4′-dinitrostilbène-2,2′-disulfonique

Canadian Journal of Chemistry ◽

10.1139/v96-159 ◽

1996 ◽

Vol 74 (7) ◽

pp. 1409-1417 ◽

Cited By ~ 1

Author(s):

Anne-Marie Martre ◽

Guy Mousset ◽

Veronica Cosoveanu ◽

Virginia Danciu

Keyword(s):

Electrochemical Behavior ◽

Chemical Reduction ◽

Redox Couple ◽

The Other ◽

Disulfonic Acid ◽

Reaction Products ◽

Redox Systems ◽

Experimental Conditions ◽

Redox Couples ◽

The One

This work concerns the electrochemical and chemical reductions of 4,4′-dinitrodibenzyl and 4,4′-dinitrostilbene 2,2′-disulfonic acid under various experimental conditions. On the one hand, the electrochemical reduction is realized on Sn, monel, and Hg electrodes with or without the presence of a redox couple, and on the other hand, the chemical reduction is performed by mean of an electrochemically generated reducing agent (Sn0). According to the type of redox couple used (Ti3+/Ti4+ or sn0/sn2+), important changes in the nature and the ratio of reaction products are observed. The best conditions for obtaining di- or monoamines are defined, they correspond to 90% yield for the diamines, 70% and 50%, respectively, for 4-amino-4′-nitrodibenzyl and for 4-amino-4′-nitrostilbene-2,2′-disulfonic acid. The electrochemical behavior of the dinitro derivatives and of TiOSO4, TiCl4, and SnCl2, used as precursors of the redox couples is studied under conditions of macroscale electrolyses (5 N H2SO4–EtOH 50/50, 2.5 N H2SO4, and 10% HCl). Key words: 4,4′-dinitrodibenzyl, 4,4′-dinitrostilbene 2,2′-disulfonic acid, electrochemistry, reduction, Ti3+/Ti4+ and Sn0/Sn2+ redox systems.

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Role of redox-inactive metals in controlling the redox potential of heterometallic manganese–oxido clusters

Photosynthesis Research ◽

10.1007/s11120-021-00846-y ◽

2021 ◽

Author(s):

Keisuke Saito ◽

Minesato Nakagawa ◽

Manoj Mandal ◽

Hiroshi Ishikita

Keyword(s):

Photosystem Ii ◽

Redox Potential ◽

Quantum Chemical Calculations ◽

Catalytic Reaction ◽

Quantum Chemical ◽

Ionic Radius ◽

Redox Potentials ◽

Oxygen Evolving ◽

Highest Occupied Molecular Orbitals

AbstractPhotosystem II (PSII) contains Ca2+, which is essential to the oxygen-evolving activity of the catalytic Mn4CaO5 complex. Replacement of Ca2+ with other redox-inactive metals results in a loss/decrease of oxygen-evolving activity. To investigate the role of Ca2+ in this catalytic reaction, we investigate artificial Mn3[M]O2 clusters redox-inactive metals [M] ([M] = Mg2+, Ca2+, Zn2+, Sr2+, and Y3+), which were synthesized by Tsui et al. (Nat Chem 5:293, 2013). The experimentally measured redox potentials (Em) of these clusters are best described by the energy of their highest occupied molecular orbitals. Quantum chemical calculations showed that the valence of metals predominantly affects Em(MnIII/IV), whereas the ionic radius of metals affects Em(MnIII/IV) only slightly.

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Detecting Redox Potentials Using Porous Boron Nitride/ATP-DNA Aptamer/Methylene Blue Biosensor to Monitor Microbial Activities

Micromachines ◽

10.3390/mi13010083 ◽

2022 ◽

Vol 13 (1) ◽

pp. 83

Author(s):

Kai Guo ◽

Zirui Song ◽

Gaoxing Wang ◽

Chengchun Tang

Keyword(s):

Methylene Blue ◽

Microbial Community ◽

Boron Nitride ◽

Redox Potential ◽

Microbial Activity ◽

Potential Change ◽

Dna Aptamer ◽

Redox Potentials ◽

Microplate Reader

Microbial activity has gained attention because of its impact on the environment and the quality of people’s lives. Most of today’s methods, which include genome sequencing and electrochemistry, are costly and difficult to manage. Our group proposed a method using the redox potential change to detect microbial activity, which is rooted in the concept that metabolic activity can change the redox potential of a microbial community. The redox potential change was captured by a biosensor consisting of porous boron nitride, ATP-DNA aptamer, and methylene blue as the fluorophore. This assembly can switch on or off when there is a redox potential change, and this change leads to a fluorescence change that can be examined using a multipurpose microplate reader. The results show that this biosensor can detect microbial community changes when its composition is changed or toxic metals are ingested.

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Temperature effects on bank filtration: redox conditions and physical-chemical parameters of pore water at Lake Tegel, Berlin, Germany

Journal of Water and Climate Change ◽

10.2166/wcc.2010.005 ◽

2010 ◽

Vol 1 (1) ◽

pp. 55-66 ◽

Cited By ~ 17

Author(s):

A. Gross-Wittke ◽

G. Gunkel ◽

A. Hoffmann

Keyword(s):

Water Temperature ◽

High Water ◽

Nitrate Respiration ◽

Redox Processes ◽

Redox Potentials ◽

Bank Filtration ◽

Physical Chemical ◽

Drinking Water Production ◽

Chemical Conditions ◽

Sediment Layers

In the city of Berlin, artificial groundwater recharge techniques, such as bank filtration and infiltration ponds, are an important source for drinking water production. Climate change with increasing surface water temperatures can influence the water purification processes during bank filtration mainly due the intensification of metabolic processes leading to a decrease of oxygen and an increase of anaerobic conditions. In Lake Tegel a significant increase of water temperature in the epilimnion of 2.4°C within the last 30 years was recorded. For a better understanding of induced bank filtration at Lake Tegel, redox processes and physical-chemical conditions within the surface sediment layers (0–26 cm depth) at the littoral infiltration zone were investigated. The influence of temperature in the range of 0–25°C on microbial catalysis of redox processes, such as reduction of nitrate and sulphate, was examined during the period March 2004–June 2005. High water temperatures (16–25°C) were accompanied by negative redox potentials (EH=−47 mV) and decreasing Ninorg concentrations, while the amount of ammonia, Mn2 + and Fe2 + was rising. This indicates redox processes such as denitrification, Mn4 + reduction, nitrate respiration and ammonification, as well as Fe3 + reduction. The reduction of sulphate, however, has not yet become significant at Lake Tegel, but with increasing water temperature, sulphate reduction must be expected.

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Temperature-induced diurnal redox potential in soil

Environmental Science Processes & Impacts ◽

10.1039/d1em00254f ◽

2021 ◽

Author(s):

Kristof Dorau ◽

Bianca Bohn ◽

Lutz Weihermüller ◽

Tim Mansfeldt

Keyword(s):

Redox Potential ◽

Temporal Resolution ◽

High Temporal Resolution ◽

Redox Potentials ◽

Soils And Sediments

With the capabilities to measure redox potentials (EH) at a high temporal resolution, scientists have observed diurnal EH that occur in a distinct periodicity in soils and sediments. These patterns...

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The Lack of Mitochondrial Thioredoxin TRXo1 Affects In Vivo Alternative Oxidase Activity and Carbon Metabolism under Different Light Conditions

Plant and Cell Physiology ◽

10.1093/pcp/pcz123 ◽

2019 ◽

Vol 60 (11) ◽

pp. 2369-2381 ◽

Cited By ~ 7

Author(s):

Igor Florez-Sarasa ◽

Toshihiro Obata ◽

Nï¿½stor Fernï¿½ndez Del-Saz ◽

Jean-Philippe Reichheld ◽

Etienne H Meyer ◽

...

Keyword(s):

Carbon Metabolism ◽

Redox State ◽

Redox Regulation ◽

Alternative Oxidase ◽

Tricarboxylic Acid Cycle ◽

Reduced Form ◽

Photosynthetic Parameters ◽

Primary Metabolism ◽

Redox Systems

Abstract The alternative oxidase (AOX) constitutes a nonphosphorylating pathway of electron transport in the mitochondrial respiratory chain that provides flexibility to energy and carbon primary metabolism. Its activity is regulated in vitro by the mitochondrial thioredoxin (TRX) system which reduces conserved cysteines residues of AOX. However, in vivo evidence for redox regulation of the AOX activity is still scarce. In the present study, the redox state, protein levels and in vivo activity of the AOX in parallel to photosynthetic parameters were determined in Arabidopsis knockout mutants lacking mitochondrial trxo1 under moderate (ML) and high light (HL) conditions, known to induce in vivo AOX activity. In addition, 13C- and 14C-labeling experiments together with metabolite profiling were performed to better understand the metabolic coordination between energy and carbon metabolism in the trxo1 mutants. Our results show that the in vivo AOX activity is higher in the trxo1 mutants at ML while the AOX redox state is apparently unaltered. These results suggest that mitochondrial thiol redox systems are responsible for maintaining AOX in its reduced form rather than regulating its activity in vivo. Moreover, the negative regulation of the tricarboxylic acid cycle by the TRX system is coordinated with the increased input of electrons into the AOX pathway. Under HL conditions, while AOX and photosynthesis displayed similar patterns in the mutants, photorespiration is restricted at the level of glycine decarboxylation most likely as a consequence of redox imbalance.

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A Critical Evaluation of the Redox Properties of Uranium, Neptunium and Plutonium Ions in Acidic Aqueous Solutions

Pure and Applied Chemistry ◽

10.1351/pac199971091771 ◽

1999 ◽

Vol 71 (9) ◽

pp. 1771-1807 ◽

Cited By ~ 37

Author(s):

Sorin Kihara ◽

Zenko Yoshida ◽

Hisao Aoyagi ◽

Kohji Maeda ◽

Osamu Shirai ◽

...

Keyword(s):

Aqueous Solutions ◽

Redox Reactions ◽

Critical Evaluation ◽

Redox Properties ◽

Redox Processes ◽

Redox Potentials ◽

Electrode Processes ◽

Reversible Redox ◽

Reduction Mechanisms ◽

Current Potential

Standard redox potentials, E0s, and redox processes of U, Np and Pu ions in acidic aqueous solutions are reviewed and evaluated critically. The E0sof reversible redox processes, MO22+/MO2+ and M4+/M3+ (M: U, Np or Pu) adopted are those proposed mainly by Riglet et al. on the basis of the precise correction of formal potentials, E0's, according to the improved theoretical approach to estimate the activity coefficient. Electrode processes of the U, Np and Pu ions are discussed in terms of current-potential curves, measured so far by polarography, voltammetry or flow coulometry. Special attention is payed to the irreversible MO2+/M4+ reactions. Disproportionation reactions of MO2+ are also discussed. New substances are introduced as intermediates during reductions of MO2+ to M4+ or disproportionations of MO2+.CONTENTSIntroductionStandard redox potentials for uranium, neptunium and plutonium ions in acidic aqueous solutions2.1 Evaluation of E0 from E0' determined by electrochemical measurements2.2 Temperature dependence of E0Redox reactions of uranium, neptunium and plutonium in acidic aqueous solutions investigated by polarography or voltammetry3.1 Uranium3.2 Neptunium3.3 Plutonium3.4 Disproportionation of NpO2+, PuO2+, Np4+ and Pu4+3.5 Reduction of MO2+ and reduction intermediatesRedox reactions of uranium, neptunium and plutonium in acidic aqueous solutions investigated by flow coulometry4.1 Electrode processes of the uranium, neptunium and plutonium ions investigated by flow coulometry at the column electrode at the column electrode4.2 Disproportionation of MO2+ during the electrolysis by flow coulometry4.3 Reduction mechanisms of MO2+ (M = Np or Pu) and reduction intermediates investigated by flow coulometryConclusionsList of abbreviationsAppendixReferences

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Site-directed mutations in fungal laccase: effect on redox potential, activity and pH profile

Biochemical Journal ◽

10.1042/bj3340063 ◽

1998 ◽

Vol 334 (1) ◽

pp. 63-70 ◽

Cited By ~ 179

Author(s):

Feng XU ◽

Randy M. BERKA ◽

Jill A. WAHLEITHNER ◽

Beth A. NELSON ◽

Jeffrey R. SHUSTER ◽

...

Keyword(s):

Redox Potential ◽

Phenol Oxidase ◽

Ascorbate Oxidase ◽

Single Mutation ◽

Redox Potentials ◽

Wild Type ◽

Ph Optimum ◽

Ph Profile ◽

Potential Activity

A Myceliophthora thermophila laccase and a Rhizoctonia solani laccase were mutated on a pentapeptide segment believed to be near the type-1 Cu site. The mutation L513F in Myceliophthora laccase and the mutation L470F in Rhizoctonia laccase took place at a position corresponding to the type-1 Cu axial methionine (M517) ligand in Zucchini ascorbate oxidase. The triple mutations V509L,S510E,G511A in Myceliophthora laccase and L466V,E467S,A468G in Rhizoctonia laccase involved a sequence segment whose homologue in ascorbate oxidase is flanked by the M517 and a type-1 Cu-ligating histidine (H512). The single mutation did not yield significant changes in the enzymic properties (including any significant increase in the redox potential of the type-1 Cu). In contrast, the triple mutation resulted in several significant changes. In comparison with the wild type, the Rhizoctonia and Myceliophthora laccase triple mutants had a phenol-oxidase activity whose pH optimum shifted 1 unit lower and higher, respectively. Although the redox potentials were not significantly altered, the Km, kcat and fluoride inhibition of the laccases were greatly changed by the mutations. The observed effects are interpreted as possible mutation-induced structural perturbations on the molecular recognition between the reducing substrate and laccase and on the electron transfer from the substrate to the type-1 Cu centre.

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Noninvasive Probing of Redox Reactions in Single Living Cells by Scanning Electrochemical Microscopy (SECM)

Microscopy and Microanalysis ◽

10.1017/s1431927600030348 ◽

2001 ◽

Vol 7 (S2) ◽

pp. 854-855

Author(s):

M. V. Mirkin ◽

B. Liu ◽

S. A. Rotenberg

Keyword(s):

Chemical Reactivity ◽

Metastatic Breast ◽

Mechanistic Explanation ◽

Living Cells ◽

Redox Activity ◽

Reduced Form ◽

Redox Potentials ◽

Redox Species ◽

Normal Human Breast ◽

Single Living Cells

We reported recently the first application of the scanning electrochemical microscope (SECM) to probe the redox activity of individual living cells. The possibilities of measuring the rate and investigating the pathway of transmembrane charge transfer (CT) were demonstrated. Significant differences were detected in the redox responses given by normal human breast epithelial cells (MCF-10A) and metastatic breast cancer cells (MDA-MB-231). Here, we demonstrate that the intracellular redox potentials and concentrations of redox components in the cell can be evaluated noninvasively by the SECM. Such measurements provide mechanistic explanation of the observed differences in cell redox activities.In SECM, a microscopic electrochemical sensor, usually called the tip, is scanned over the surface of a sample, and topographic images and maps of chemical reactivity across the surface are obtained. The schematic diagram of such measurements is shown in Figure 1. The oxidized (or reduced) form of redox species initially present in solution reacts at the surface of the ultramicroelectrode tip.

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