The electrochemistry of short-lived intermediate species

Benderskiĭ, V. A.; Krivenko, A. G.

doi:10.1070/rc1990v059n01abeh003506

Cited by 38 publications

(84 citation statements)

References 20 publications

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“…The reduction potential of NO measured by the photoelectrochemical technique has been reported as E 0 (NO͞NO Ϫ ) ϭ Ϫ0.81 V vs. NHE without specifying the NO Ϫ spin state (21). This value is consistent with the upper limit E 0 (NO͞NO Ϫ ) Ͻ Ϫ0.7 V vs. NHE that can be inferred from the onset of the irreversible NO reduction wave observed in controlled-potential coulometry (20).…”

Section: Resultssupporting

confidence: 73%

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Nitroxyl and its anion in aqueous solutions: Spin states, protic equilibria, and reactivities toward oxygen and nitric oxide

Shafirovich

Lymar

2002

Proc. Natl. Acad. Sci. U.S.A.

409

496

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The thermodynamic properties of aqueous nitroxyl (HNO) and its anion (NO ؊ ) have been revised to show that the ground state of NO ؊ is triplet and that HNO in its singlet ground state has much lower acidity, pKa( 1 HNO͞ 3 NO ؊ ) Ϸ 11.4, than previously believed. These conclusions are in accord with the observed large differences between 1 HNO and 3 NO ؊ in their reactivities toward O2 and NO. Laser flash photolysis was used to generate 1 HNO and 3 NO ؊ by photochemical cleavage of trioxodinitrate (Angeli's anion). The spin-allowed addition of 3 O2 to 3 NO ؊ produced peroxynitrite with nearly diffusion-controlled rate (k ‫؍‬ 2.7 ؋ 10 9 M ؊1 ⅐s ؊1 ). In contrast, the spin-forbidden addition of 3 O2 to 1 HNO was not detected (k Ͻ Ͻ 3 ؋ 10 5 M ؊1 ⅐s ؊1 N itroxyl (HNO, also known as nitrosyl hydride) and its anion, NO Ϫ , are the simplest molecules with nitrogen in the ϩ1 oxidation state and yet their aqueous chemistry is not well understood. Recent suggestions that these redox neighbors of the biologically important NO radical may play a role in cellular metabolism (1-4) and in aerobic environments may be precursors to cytotoxic peroxynitrite, ONOO Ϫ , (5, 6) have engendered considerable interest in the chemistry of HNO͞NO Ϫ . The characterization of these species is complicated by their instability with respect to formation of nitrous oxide (7,8). In most cases where nitroxyl has been invoked as an intermediate, the rate-determining step was its generation, a situation that allows little insight into the properties and reactivities of HNO͞NO Ϫ themselves. The NO Ϫ anion is isoelectronic with O 2 and, like O 2 , should have a triplet ground state, whereas the ground state of HNO should be a singlet. Indeed, these ground state assignments have been well established for HNO͞NO Ϫ in the gas phase (9, 10).A frequently used source for aqueous HNO͞NO Ϫ is trioxodinitrate (N 2 O 3 2Ϫ , also known as Angeli's anion), whose conjugate acid (H 2 N 2 O 3 ) has consecutive pKa values of 2.5 and 9.7 (11). It is widely accepted (7, 8) that slow decomposition of the monoprotonated anion occurs through heterolytic NON bond cleavageSubsequent addition of O 2 could yield peroxynitriteHowever, nitrate, which is the peroxynitrite decomposition product, was not detected among the end products of HN 2 O 3 Ϫ decay (12). This result was interpreted as evidence against the occurrence of reaction 2. On the other hand, the same researchers reported peroxynitrite formation during N 2 O 3 2Ϫ photolysis in alkaline solution (13). To reconcile the data, it was suggested that thermal reaction 1 followed by deprotonation of HNO produces singlet NO Ϫ , which is the ground state in water, and that 1 NO Ϫ is unreactive toward O 2 . In contrast, photochemical cleavage of N 2 O 3 2Ϫ was thought to generate the long-lived triplet excited state of NO Ϫ , which reacted with O 2 . However, it seems unlikely that hydration can reverse a gas-phase energy gap of about 70 kJ͞mol between the ground state 3 NO Ϫ and the excited state 1 NO Ϫ (10). Moreover, by ana...

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Section: Resultssupporting

confidence: 73%

“…The estimates for the reduction potential of the NO͞NO Ϫ couple based on this value (19) are almost a volt higher than those obtained by electrochemical techniques (20,21); this discrepancy has never been addressed. Recent ab initio calculations placed the pKa of HNO at 7.2 (22).…”

mentioning

confidence: 78%

Nitroxyl and its anion in aqueous solutions: Spin states, protic equilibria, and reactivities toward oxygen and nitric oxide

Shafirovich

Lymar

2002

Proc. Natl. Acad. Sci. U.S.A.

409

496

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“…2. Theoretical calculations [26,28] as well as physical measurements [29] demonstrated a low potential ca. À0.8 V (at 1 M versus NHE) for the reduction of NO to nitroxyl anion ( 3 NO À ), a substantial revision of the widely cited values of +0.39 V and À0.…”

Section: Hno Revisitedmentioning

confidence: 98%

Coordination chemistry of the HNO ligand with hemes and synthetic coordination complexes

Farmer

Sulc

2005

Journal of Inorganic Biochemistry

138

179

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“…( Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002) formed by an oxidative pathway, due to the low reduction potential of the · NO/NO ؊ couple (E ϭ Ϫ0.80 V in water vs. SCE). [18] · NO derivatives are more reactive: peroxynitrite (ONOO ؊ ) is, in fact, a strong oxidant (E°O NOO -/ · NO2 ϭ 1.60 V in water) [19,20] and nitrosodioxidanyl (ONOO · ) could act as hydrogen abstractor, the BDE of HϪONOO being 423.22 kJ/mol, but is not a very good oxidant: the reduction potential for the ONOO · /ONOO ؊ couple is E 1/2 ϭ 0.35 Ϯ 0.02 V vs. SSCE. [21] Nitrosodioxidanyl rapidly reacts with · NO to afford two molecules of · NO 2 .…”

Section: Introductionmentioning

confidence: 99%

On the Role of Nitrogen Monoxide (Nitric Oxide) in the Nitration of a Tyrosine Derivative and Model Compounds

Giorgini¹,

Petrucci

Astolfi³

et al. 2002

Eur. J. Org. Chem.

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The nitration of tyrosine derivatives with nitrogen monoxide (nitric oxide) occurs only in the presence of dioxygen, and the hypothesized mechanism involves nitrogen dioxide (·NO2). For better understanding of the reaction mechanism, the nitration of model compounds − such as 1‐ and 2‐naphthols and their corresponding 2‐ and 1‐nitroso derivatives − with nitrogen monoxide in the presence and in the absence of dioxygen was studied. The results described here show that tyrosine and naphthols do not undergo nitrosation when they react with ·NO, and so nitrosation of tyrosine in biological systems is highly unlikely. In addition, the oxidation of nitrosonaphthols ←⇄ isonitrosonaphthols by nitric oxide and its derivatives to the corresponding nitro derivatives does not involve the oxoammonium ion, as reported previously. The mechanistic proposals are supported mainly by ESR investigation and electrochemical data. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

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The electrochemistry of short-lived intermediate species

Cited by 38 publications

References 20 publications

Nitroxyl and its anion in aqueous solutions: Spin states, protic equilibria, and reactivities toward oxygen and nitric oxide

Nitroxyl and its anion in aqueous solutions: Spin states, protic equilibria, and reactivities toward oxygen and nitric oxide

Coordination chemistry of the HNO ligand with hemes and synthetic coordination complexes

On the Role of Nitrogen Monoxide (Nitric Oxide) in the Nitration of a Tyrosine Derivative and Model Compounds

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