Superoxide Complex Research Articles

Quantitative Evaluation of Lewis Acidity of Organotin Compounds and the Catalytic Reactivity in Electron Transfer

Abstract The g-values of ESR spectra of superoxide (O2•−) complexes with various organotin compounds acting as Lewis acids were determined in acetonitrile at 143 K. The binding energies (ΔE) in the complexes between organotins and O2•− have been evaluated from deviation of the gzz-values from the free spin value. The ΔE values are well correlated with the catalytic reactivity of organotins as well as a series of metal ions acting as Lewis acids to promote electron transfer from cobalt(II) tetraphenylporphyrin to O2, which would not occur in the absence of Lewis acids under otherwise the same experimental conditions.

Quantitative Evaluation of Lewis Acidity of Zinc Ion with Tetradentate Tripodal Ligands in Formation of the Superoxide Complexes

Abstract A series of Zn(II)–superoxide complexes containing tetradentate tripodal ligands are generated in the reactions between Zn(II) complexes and superoxide which is produced by the photoinduced reduction of dioxygen by dimeric 1-benzyl-1,4-dihydronicotinamide. The Zn(II)–superoxide complexes have been characterized spectroscopically in order to evaluate the Lewis acidity of Zn(II) ion depending on the ligands used as Cu,Zn–SOD models.

Lanthanide superoxide complexes and a novel μ 3-oxo samarium complex with hydrotris(3,5-dimethylpyrazolyl)borate ligand

The lanthanide superoxide complexes Tp 2Sm(η 2-O 2) ( 1) (Tp=hydrotris-(pyrazolyl)borate), Tp 2Yb(η 2-O 2) ( 2) and Tp* 2Yb(η 2-O 2) ( 3) [Tp*=hydrotris(3,5-dimethylpyrazolyl)borate], have been synthesized by the reactions of Tp 2Sm, Tp 2Yb and Tp* 2Yb with dioxygen in toluene at −75°C, respectively. The reaction of Tp* 2Sm with a half equivalent of pyridine N-oxide in THF yields complex [Tp* 2Sm] 2(μ-η 2:η 2-O 2)·2THF ( 4) . The addition of hexane to the mother liquid, which was generated after the separation of complex 4, yields crystals of [Tp*Pz* 2-Sm(μ 3-O)(BOH)] 2·2THF ( 5) (Pz*=3,5-dimethylpyrazolyl) structurally characterized by X-ray diffraction. Meanwhile 3,5-dimethylpyrazole resulted from the cleaved Tp* was also detected. Complex 5 is a seven-coordinated dimeric molecule with a pseudo-octahedral coordination geometry and crystallizes in the triclinic space group P1̄ (no. 2) with a=13.458(4) Å, b=13.740(5) Å, c=10.198(3) Å, α=105.88(3)°, β=107.99(2)°, γ=86.85(3)°, Z=1. The samarium to nitrogen distances range from 2.516(5) to 2.624(5) Å. The samarium to oxygen distances are 2.249(4)–2.324(4) Å. The complex contains two Tp*, four Pz*, two samarium atoms and two bridged oxygen atoms.

The exogenous NADH dehydrogenase of heart mitochondria is the key enzyme responsible for selective cardiotoxicity of anthracyclines.

The molecular mechanism of the anthracycline-dependent development of cardiotoxicity is still far from being clear. However, it is generally accepted, that mitochondria play a significant role in triggering this organ specific injury. The results presented in this study demonstrate that, in contrast to liver mitochondria, isolated heart mitochondria shuttle single electrons to adriamycin, giving rise to oxygen radical formation via autoxidation of adriamycin semiquinones. This one electron reduction of anthracyclines is catalyzed by the exogenous NADH dehydrogenase associated with complex I of heart mitochondria, an enzyme which is lacking in liver mitochondria. Upon addition of NADH heart mitochondria generate significant amounts of adriamycin semiquinones while liver mitochondria were ineffective. Adriamycin semiquinones undergo both autoxidation leading to superoxide radical release and complex reactions under formation of adriamycin aglycone. Due to the high lipophilicity adriamycin aglycones accumulate in the inner mitochondrial membrane where they interfere with electron carriers of the respiratory chain. Adriamycin aglycone semiquinones emerging from an interaction with complex I were found to trigger homolytic cleavage of H2O2 which results in the formation of hydroxyl radicals. As demonstrated in this study the activation of adriamycin by the exogenous NADH dehydrogenase of cardiac mitochondria initiates a cascade of reaction steps leading to the establishment of oxidative stress. Our experiments suggest the exogenous NADH dehydrogenase of heart mitochondria to play a key role in the cardiotoxicity of adriamycin. This organ-specific enzyme initiates a sequence of one electron transfer reactions ending up in the establishment of oxidative stress.

Oxidation of manganese(II) by ozone and reduction of manganese(III) by hydrogen peroxide in acidic solution

Manganese(II) is oxidized by ozone in acid solution, k=(1.5±0.2)×103 M−1 s−1 in HClO4 and k=(1.8±0.2)×103M−1 s−1 in H2SO4. The plausible mechanism is an oxygen atom transfer from O3 to Mn2+ producing the manganyl ion MnO2+, which subsequently reacts rapidly with Mn2+ to form Mn(III). No free OH radicals are involved in the mechanism. The spectrum of Mn(III) was obtained in the wave length range 200–310 nm. The activation energy for the initial reaction is 39.5 kJ/mol. Manganese(III) is reduced by hydrogen peroxide to Mn(II) with k(Mn(III)+H2O2)=2.8×103M−1 s−1 at pH 0–2. The mechanism of the reaction involving formation of the manganese(II)-superoxide complex and reaction of H2O2 with Mn(IV) species formed due to reversible disproportionation of Mn(III), is suggested. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 207–214, 1998.

Manganese(II)−Superoxide Complex in Aqueous Solution

Mn(II)aq−superoxide complex, MnO2+, was formed in pulse radiolysis by three distinct routes: Mn(I) + O2, Mn(II) + O2- and Mn(III) + H2O2. The stability of this complex was found to be governed by the two equilibria: Mn2+ + O2- ⇌ MnO2+ (1,−1) and Mn2+ + HO2 ⇌ MnO2+ + H+ (6,−6). Both forward and reverse rate constants of the reactions involved in these equilibria were determined: k1 = (1.5 ± 0.2) × 108 M-1 s-1, k-1 = (6.5 ± 1.0) × 103 s-1; k6 = (1.1 ± 0.2) × 106 M-1 s-1, k-6 = (6.5 ± 1.0) × 106 M-1 s-1, yielding K1,-1 = (2.3 ± 0.5) × 104 M-1 and K6,-6 = 0.17 ± 0.06. The metal−oxy complex MnO2+ decays by self-reaction with k(MnO2+ + MnO2+) = (6.0 ± 1.0) × 106 M-1 s-1 and in acid solutions also by reaction with HO2, k(MnO2+ + HO2) = (1.0 ± 0.3) × 107 M-1 s-1. In both cases stoichiometric amounts of H2O2 are formed as the end product. Mn(I) was formed by reduction of Mn2+ with H atoms. It has an absorption spectra with maxima at 290 and 340 nm with e290 = 1300 ± 200 M-1 cm-1 and e340 = 1000 ± 150 M-1 cm-1. ...

Effect of paraquat on the malondialdehyde level in rat liver microsomes (in vitro).

Toxicosis due to paraquat, a redox cycling xenobiotic, is still a subject of much debate. In the present study on lipid peroxidation, paraquat had a biphasic effect on the malondialdehyde (MDA) level in rat liver microsomes; stimulation at the initial stage (within 10 min) and depression at the later stage. Although paraquat increased the initial rate of NADPH oxidation dose-dependently, the rate was not necessarily parallel with the increase in the MDA level. The MDA level increased linearly up to 0.1 mM paraquat added, but then it attained a plateau. The stimulation obtained by paraquat within 10 min was absolutely dependent on exogenous Fe2+ ion and NADPH, and the stimulation was entirely SOD sensitive, while the iron-driven increase in MDA was 20% sensitive. Thus, there were different mechanisms between iron-driven lipid peroxidation and paraquat-modified peroxidation. Catalase increased the level, but mannitol, a scavenger of OH, had no effect. EPR spectra showed that superoxide was formed dose-dependently up to 0.1 mM paraquat and that it attained a plateau at the same as MDA level described above. From these results, we concluded that paraquat stimulates lipid peroxidation through a mechanism dependent on the superoxide complex involving Fe2+ ion.

Synthesis, characterization and reactivity of Claus' blue, a superoxodirhodium(III,III) species long said to contain Rh VI

Spectroscopic study of the ill defined Claus' blue, ‘[RhVIO4]2–’, and the better characterized [RhIII2(OH)2(H2O)n(µ-O2)]3+ ion has revealed that the two ostensibly very different syntheses involved both give aquasuperoxorhodium(III) species; the properties of the two products are compared and contrasted. The O–O link in Claus' blue derives from the oxidation of co-ordinated hydroxide to give a peroxo-, then a superoxo-form. The properties of Claus' blue are rationalized in terms of its synthesis. The [RhIII(O2)RhIII]5+ core can be utilized to form other rhodium(III) superoxide complexes.

Electrochemical and photoelectrochemical characterization of naturally grown oxide layers on copper in sodium acetate solutions with and without benzotriazole

The aim of this work is the characterization of as-grown oxide layers of copper in aerated sodium acetate solutions, in relation to the understanding of the mechanism of protection in the presence of benzotriazole, which is a well known inhibitor of corrosion. The growth and the characteristics of the film at rest potential are studied using cathodic stripping analysis in a deaerated solution. Its properties are determined by using the photoelectrochemical technique. It is shown that in BTA solution, the photoactive layer is the same as without BTA, giving the same optical indirect transitions at 2.6 and 1.9 eV, its thickness being in the range of a few nm. Both cathodic and anodic photocurrents are generated and the particular dependence of the spectral response as a function of potential is evidenced and explained. At the rest potential both photocurrents are superimposed. The layer is attributed to cuprous oxide, weakly modified with BTA. In the presence of BTA, changes in the reduction curves are observed and special attention is paid to a cathodic wave in excess, specific to BTA-aerated solutions. The formation of a polymeric copper(I)-BTA outer film is suggested for the formation of a Cu(II)-superoxide complex related to the uptake of molecular dioxygen.

Kinetics of a rapid, luminol dependent chemiluminescence signal induced in HL-60 cells by amphotericin B and other stimulants

Addition of the polyene antibiotic amphotericin B or tissue culture medium to nondifferentiated HL-60 cells in the presence of luminol induces a chemiluminescence signal that reaches a peak value within a few seconds and decays exponentially in less than a minute. The kinetics of the signal and its modulation by superoxide dismutase, catalase, and horseradish peroxidase are consistent with a series of solution biochemical processes with a rate-determining step corresponding to the disproportionation of a luminol-superoxide complex. The effects of the enzymes demonstrate that superoxide is a precursor to the rate-determining intermediate and that both catalase and peroxide enhance a reaction that competes with the rate-limiting process.

Autoxidation of the serotonergic neurotoxin 5,7-dihydroxytryptamine

The indolic neurotoxin 5,7-dihydroxytryptamine (5,7-DHT) has been widely speculated to express its neurodegenerative effects as a result of intraneuronol autoxidation. Until recently, it was believed that autoxidation led to reactive electrophilic quinone imine species which alkylated neuronal membrane proteins and that byproducts of the autoxidation reaction were cytotoxic reduced-oxygen species. This study reveals that at physiological pH carbanions of 5,7-DHT act as the primary electron-donor species to yield C(4)- and C(6)-centered free radical superoxide complexes in a 1:2 ratio. The C(4)-centered complex reacts to yield, ultimately, 5-hydroxytryptamine-4,7-dione which has been shown to be a significantly more powerful neurotoxin than 5,7-DHT. The C(6)-centered radical superoxide complexes react to give 6,6'-bis(5-hydroxytryptamine-4,7-dione). It is likely that the latter reaction yields O2.- as a cytotoxic byproduct.

ChemInform Abstract: ESR Evidence of the Formation of a New Superoxide Complex of Tetra‐p‐tolylporphyrinatocobalt(II) in Aprotic Solvents.

AbstractESR studies on the reactions of the title complex (I) show that in the absence of oxygen in DMSO solution the adduct (II) is formed.

ESR evidence of the formation of a new superoxide complex of tetra- p-tolyporphyrinatocobalt(II) in aprotic solvents

The reactions of the superoxide ion (O 2 −) with tetra- p-tolyporphyrinatocobalt(II) [Co(II)TTP] in dimethyl sulfoxide(DMSO) have been investigated by use of electron spin resonance (ESR) spectroscopy. In the absence of oxygen, Co(II)TTP in DMSO gives the DMSO adduct, Co(II)(TPP)(DMSO). When this DMSO adduct is exposed to air, an oxygen complex, Co(II)(TTP)(DMSO)(O 2), is formed in which the binding state between Co(II) and O 2 has been considered formally as Co(III)O 2 −. When the superoxide ion (O 2 − is added to this oxygen complex, a new superoxide complex, Co(II)(TTP)(O 2 −) 2, is formed. The same superoxide adduct is formed by the reaction of O 2 − with Co(II)TTP in the absence of oxygen.

Superoxide complexes of tetrakis(.mu.-2-anilinopyridinato)dirhodium(II,II) and -dirhodium(II,III): the one-electron catalytic reduction of dioxygen

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSuperoxide complexes of tetrakis(.mu.-2-anilinopyridinato)dirhodium(II,II) and -dirhodium(II,III): the one-electron catalytic reduction of dioxygenJohn L. Bear, C. L. Yao, F. J. Capdevielle, and K. M. KadishCite this: Inorg. Chem. 1988, 27, 21, 3782–3785Publication Date (Print):October 1, 1988Publication History Published online1 May 2002Published inissue 1 October 1988https://doi.org/10.1021/ic00294a022RIGHTS & PERMISSIONSArticle Views117Altmetric-Citations23LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (461 KB) Get e-Alerts Get e-Alerts

Catalytic oxidation of reduced sulfur compounds by homogeneous and heterogeneous Co(II) phthalocyanine complexes

An overview of the kinetics and mechanisms of the reactions of reduced sulfur compounds and other reductants with molecular oxygen as catalyzed by homogeneous and heterogeneous metal phthalocyanine complexes is presented. Catalysis of the autoxidation of S(IV) by Co(II) tetrasulfophthalocyanine was characterized in terms of an ordered ternary-complex mechanism in which S(IV) and oxygen are simultaneously bound to the Co(II)/Co(III) metal center. Hydrogen peroxide was identified as an intermediate reduction product of bound dioxygen. The reaction was examined by spectrophotometric and EPR methods and was found to proceed via a sulfito-cobalt(III)-superoxide complex that subsequently combines with a second sulfite molecule to produce sulfate and a sulfito-cobalt(III)-peroxide. The catalytic cycle is closed by the regeneration of the cobalt(II) complex via the production of H 2O 2. Direct evidence for he active sulfito-cobalt(III)-superoxide intermediate was obtained.

Interaction between copper(II)-arginine complexes and HO2/O2- radicals, a pulse radiolysis study

Superoxide radicals were shown to react with all four Cu(II)-arginine complexes that exist between pH 1.5 and 12.5; k/sub 10/(O/sub 2//sup -/ + CuArgH/sup 2 +/) = 3.3 x 10/sup 9/ M/sup -1/ s/sup -1/, k/sub 12/(O/sub 2//sup -/ + Cu(ArgH)/sub 2//sup 2 +/) = 1.3 x 10/sup 7/ M/sup -1/ s/sup -1/, k/sub 13/(O/sub 2//sup -/ + CuArg/sub 2/H/sup +/) = 1 x 10/sup 6/ M/sup -1/ s/sup -1/, k/sub 14/(O/sub 2//sup -/ + CuArg/sup +/) = 1 x 10/sup 8/ M/sup -1/ s/sup -1/. The system was studied in detail at pH 2.0 and pH greater than or equal to7. At low pH the mechanism was shown to proceed via a CuO/sub 2/H/sup 2 +/ complex while at higher pH a superoxide complex of the Cu(II)-arginine complexes was formed. The results are discussed in terms of the currently accepted mechanism by which SOD-Cu/sup 2 +/ dismutates O/sub 2//sup -/ radicals.

Catalytic oxidation of epinephrine at pH 8; conversions of the catalyst-Co-complex of porphin

1. A diamagnetic oxygen complex of a cobalt porphyrinate, probably possessing a peroxide tructure, was detected in aqueous solution. The coordination of epinephrine or DMFA causes a breakdown of this compound with the formation of a paramagnetic Superoxide complex. 2. The breakdown of the porphyrin macrocycle in the course of the oxidation of epinephrine occurs under the action of its oxidation products.

Copper-dioxygen chemistry. Synthesis, spectroscopy, and properties of a copper(II) superoxide complex

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCopper-dioxygen chemistry. Synthesis, spectroscopy, and properties of a copper(II) superoxide complexJeffery S. ThompsonCite this: J. Am. Chem. Soc. 1984, 106, 14, 4057–4059Publication Date (Print):July 1, 1984Publication History Published online1 May 2002Published inissue 1 July 1984https://doi.org/10.1021/ja00326a043RIGHTS & PERMISSIONSArticle Views277Altmetric-Citations35LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (402 KB) Get e-Alerts Get e-Alerts

Electrochemistry and Reactions of Transition Metal and Oxygen Ions in Dimethyl Sulfoxide

Electrochemical studies of oxygen and transition metal ions in dimethyl sulfoxide solution indicate that the , Cu2+/Cu+, and Fe3+/Fe2+ couples are reversible while the Fe2+/Fe, Co2+/Co, Ni2+/Ni, Cu+/Cu, and Mn2+/Mn couples are irreversible. The Cr3+/Cr2+ and Mn3+/Mn2+ systems are difficult to characterize and formed from undergoes slow degradation. As predicted from the electrode potentials, Cu2+ and Fe3+ are able to oxidize to oxygen. However, the reactions stop with the formation of mixed oxidation state superoxide complexes in solution. Cr3+ does not react with but forms an insoluble compound with .

Resonance Raman studies of transition metal peroxo complexes: 4‐The potassium μ‐Peroxo‐bis[pentacyanocobaltate(III)], K6[(CN)5CoO2Co(CN)5]·H2O and μ‐superoxo‐bis‐[pentacyanocobaltate(III)], K5[(CN)5CoO2Co(CN)5]·H2O complexes

AbstractResonance Raman spectra for the peroxide K6[(CN)5CoO2Co(CN)5]·H2O and superoxide K5[(CN)5CoO2Co(CN)5]·H2O complexes have been determined using several different excitation wavelengths. The peroxide spectrum shows a number of strong resonance bands at 141, 174, 408, 602, 804, 1594 and 2369 cm−1 which are assigned to the vibrational modes of the central unit CCoO2CoC (C of the axial CN) as δ(OCoC), δ(CoO2), ν(CoC), ν(CoO), ν(OO), 2ν(OO) and 3ν(OO), respectively. This is confirmed by the measurements of the 18O‐enriched complex. Intensity excitation profiles of these bands demonstrate that the resonance effect is associated with a CT transition of the type O22− ‐Co3+ assigned at 327 nm and that the carbon atoms of the two trans axial cyanides are involved in this electronic transition. The ν(OO) harmonic frequency (ω1) and anharmonicity constant (X11) are shown to be 818 and −7 cm−1, respectively. The superoxide spectrum shows a band at ∼1100 cm−1 assigned to the ν(OO) mode. The resonance effect of this band is shown to be associated with the O2− ‐Co3+ CT transition assigned at 485 nm. For both complexes, plots of [IJcorr]1/2 against the Shorygin function [1+ (νexc/νe)2]/[‐(νexc/νe)2]2 give straight lines from which the value of α′ for OO band in the superoxide is calculated to be twice as big as that in the peroxide complex. This is in agreement with the calculated force constants which show that the superoxide link is ∼1.93 times stronger than the peroxide link, while the CoO is ∼1.4 times weaker in the superoxide complex. Infrared absorption measurements show no bands that are related to ν(OO) or ν (CoO) in either of the complexes.