Oxygen atom transfer promoted nitrate to nitric oxide transformation: a step-wise reduction of nitrate → nitrite → nitric oxide

Kulbir,; Das, Sandip Kumar; Devi, Tarali; Goswami, Mrigaraj; Yenuganti, Mahesh; Bhardwaj, Prabhakar; Ghosh, Somnath; Sahoo, Subash Chandra; Kumar, Pankaj

doi:10.1039/d1sc00803j

Cited by 30 publications

(22 citation statements)

References 78 publications

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“…Evans method analysis in CD 3 CN at 298 K provides the solution magnetic moment of 2 as 4.40 μ B , which suggests the presence of a high-spin Co II site (d 7 , S = 3/2) in 2 . In the absence of a crystal structure of 2 , we propose an O -bound nitrite at the Co II site in accordance with the previous reports on cobalt(II)-nitrite and metal(II)-nitrite complexes supported by amine-donor ligands. ,,, …”

Section: Resultssupporting

confidence: 91%

“…For assessing the relatively lower yield of NO gas from the reaction of 1 , the FT-IR spectrum of the ( Bz 3 Tren )Co end-product was inspected for the possible formation of cobalt-nitrosyl species {CoNO} 8 . In the absence of any distinct vibrational feature around ∼1700 cm –1 , we rule out the generation of {CoNO} 8 (Figure S21). Furthermore, in contrast to the previously illustrated N 2 O formation from the reaction of AH 2 and nitrite at a porphyrazine-Co II and Cu II sites, , gas-phase FT-IR analyses of the headspace on ( 1 + AH 2 /DTBC) reaction mixtures do not show any detectable N 2 O (Figure S27).…”

Section: Resultsmentioning

confidence: 97%

“…A cobalt-tripeptide complex serves as a functional mimic of cytochrome c nitrite reductase and exhibits efficient electrocatalytic reduction of nitrite to ammonium selectively at a near neutral pH . Oxygen-atom-transfer-mediated transformation of cobalt-nitrite to cobalt-nitrosyl has been depicted recently in the presence of strong oxophilic VCl 3 . The previous illustrations of chemical reductions of nitrite typically employ exogenous reducing agents such as thiols, phosphines, H 2 S, phenols, and catechol. − However, the insights into ene-diol-mediated nitrite reduction remain in its infancy. − Herein, this report employs mononuclear cobalt(III)- and cobalt(II)-nitrite complexes ( 1 and 2 ) of a tripodal ligand Bz 3 Tren to illustrate NO generation from the cross-talks between nitrite and ene-diols such as l -ascorbic acid (AH 2 ), gallic acid (GAH 2 ), and 3,5-di- tert -butylcatechol (DTBC) (Scheme ).…”

Section: Introductionmentioning

confidence: 99%

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NO Generation from the Cross-Talks between Ene-diol Antioxidants and Nitrite at Metal Sites

et al. 2022

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The one-electron reduction of nitrite (NO 2 − ) to nitric oxide (NO) and ene-diol oxidation are two important biochemical transformations. Employing mononuclear cobalt-nitrite complexes with Co III and Co II oxidation states, [(Bz 3 Tren)Co III (nitrite) 2 ](ClO 4 ) (1) and [(Bz 3 Tren)Co II (nitrite)](ClO 4 ) (2), this report illustrates NO release coupled to stepwise oxidation of ene-diol antioxidants such as L-ascorbic acid (AH 2 ) and catechol. Analysis of the AH 2 end-product reveals that the reaction with complex 1 affords dehydroascorbic acid. Intriguingly, a controlled oxidation of AH 2 with complex 2 results in a [Co II ]-bound ascorbyl radical-anion (8). Finally, NO release with the concomitant generation of metal-bound 3,5-di-tert-butyl-semiquinone radical anion from the reactions of 3,5-di-tert-butyl-catechol and [(Bz 3 Tren)-M II (nitrite)](ClO 4 ) (2, M = Co; 4, M = Zn) provides mechanistic insights into the cross-talk between nitrite and ene-diols at the metal sites.

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Section: Resultssupporting

confidence: 91%

Section: Resultsmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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NO Generation from the Cross-Talks between Ene-diol Antioxidants and Nitrite at Metal Sites

et al. 2022

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“…Electrocatalytic NO 3 – reduction by [Cr(cyclam)Cl 2 ] + has been proposed to involve the [Cr V ]-oxo intermediate . A set of recent reports illustrates deoxygenation of NO 3 – at relatively less oxophilic transition metal sites (e.g., Co and Ni) typically in the presence of a wide range of oxophilic reagents including CO, (Bpin) 2 (pyrazine), and VCl 3 . − While the reduction of NO 3 – at late transition metal sites remains rare and commonly realized with the usage of oxophilic reagents, − the developments of metal-based NO 3 – reducing processes are challenging due to weakly coordinating and the chemically inert nature of NO 3 – . In contrast, NO 2 – anion exhibits stronger binding affinity toward metal and offers more diverse reactivity patterns in comparison to NO 3 – . − Accordingly, the reductions of nitrite at metal sites have been demonstrated in the presence of a wide range of reducing agents including thiols, − H 2 S, phosphines, − phenols, − and ene-diols. − It is noteworthy that the reaction of hydrazine (N 2 H 4 ) and nitrate in the presence of copper(II) salts has been known in the literature for several decades. , More specifically, N 2 H 4 in alkaline conditions leads to copper(II)-mediated transformation of nitrate to nitrite in good yield, thereby enabling estimation of nitrate in water samples .…”

Section: Introductionmentioning

confidence: 99%

Nitrate and Nitrite Reductions at Copper(II) Sites: Role of Noncovalent Interactions from Second-Coordination-Sphere

et al. 2022

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Reductions of nitrate and nitrite (NO x –) are of prime importance in combatting water pollution arising from the excessive use of N-rich fertilizers. While examples of NO x – reductions are known, this report illustrates hydrazine (N2H4)-mediated transformations of NO x – to nitric oxide (NO)/nitrous oxide (N2O). For nitrate reduction to NO, initial coordination of the weakly coordinating NO3 – anion at [(mC)CuII]2+ cryptate has been demonstrated to play a crucial role. A set of complementary analyses (X-ray diffraction and Fourier-transform infrared spectroscopy (FTIR), UV–vis, and NMR spectroscopies) on NO3 –-bound metal-cryptates [(mC)MII(NO3)](ClO4) (1-M, M = Cu/Zn) demonstrates the binding of NO3 – through noncovalent (NH···O, CH···O, and anion···π) and metal–ligand coordinate interactions. Subsequently, reactions of [(mC)CuII(14/15NO3)](ClO4) (1-Cu or 1-Cu/ 15 N) with N2H4·H2O have been illustrated to reduce 14/15NO3 – to 14/15NO. Intriguingly, in the absence of the second-coordination-sphere interactions, a closely related coordination motif [(Bz 3 Tren)CuII]2+ (in 3-Cu) does not bind NO3 – and is unable to assist in N2H4·H2O-mediated NO3 – reduction. In contrast, nitrite coordinates at the tripodal CuII sites in both [(mC)CuII]2+ and [(Bz 3 Tren)CuII]2+ irrespective of the additional noncovalent interactions, and hence, the N2H4 reactions of the copper(II)-nitrite complexes [(mC)CuII(O14/15NO)]+ and [(Bz 3 Tren)CuII(O14/15NO)]+ (in 2-Cu/4-Cu) result in a mixture of 14/15NO and N14/15NO.

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“…The increase in anthropogenically derived nitrogen oxyanions has led to a variety of economic and environmental problems, including large algal blooms in eutrophic bodies of water, inducing hypoxia and often leading to dead zones. − Mitigation of this eutrophication has been approached through photochemical, − electrochemical, − and chemical reduction of nitrogen oxyanions. − One approach involves reductive borylation (Scheme ) where equimolar bis(boryl)pyrazine reagent removes oxygen, as (Bpin) 2 O, because of the affinity of boron for oxygen. Our group has recently shown several examples of reductive deoxygenation using reduced N-heterocycles, − including deoxygenation of a nickel complex to induce N–N bond formation …”

Section: Introductionmentioning

confidence: 99%

An Integrated View of Nitrogen Oxyanion Deoxygenation in Solution Chemistry and Electrospray Ion Production

et al. 2021

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There has been an increasing interest in chemistry involving nitrogen oxyanions, largely due to the environmental hazards associated with increased concentrations of these anions leading to eutrophication and aquatic “dead zones”. Herein, we report the synthesis and characterization of a suite of MNO x complexes (M = Co, Zn: x = 2, 3). Reductive deoxygenation of cobalt bis(nitrite) complexes with bis(boryl)pyrazine is faster for cobalt than previously reported nickel, and pendant O-bound nitrito ligand is still readily deoxygenated, despite potential implication of an isonitrosyl primary product. Deoxygenation of zinc oxyanion complexes is also facile, despite zinc being unable to stabilize a nitrosyl ligand, with liberation of nitric oxide and nitrous oxide, indicating N–N bond formation. X-ray photoelectron spectroscopy is effective for discriminating the types of nitrogen in these molecules. ESI mass spectrometry of a suite of M(NO x ) y (x = 2, 3 and y = 1, 2) shows that the primary form of ionization is loss of an oxyanion ligand, which can be alleviated via the addition of tetrabutylammonium (TBA) as a nonintuitive cation pair for the neutral oxyanion complexes. We have shown these complexes to be subject to deoxygenation, and there is evidence for nitrogen oxyanion reduction in several cases in the ESI plume. The attractive force between cation and neutral is explored experimentally and computationally and attributed to hydrogen bonding of the nitrogen oxyanion ligands with ammonium α-CH2 protons. One example of ESI-induced reductive dimerization is mimicked by bulk solution synthesis, and that product is characterized by X-ray diffraction to contain two Co(NO)2 + groups linked by a highly conjugated diazapolyene.

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Oxygen atom transfer promoted nitrate to nitric oxide transformation: a step-wise reduction of nitrate → nitrite → nitric oxide

Abstract: Nitrate reductases (NRs) are molybdoenzymes that reduce nitrate (NO3−) to nitrite (NO2−) in both mammals and plants. In mammals, the salival microbes take part in the generation of the NO2−...

Cited by 30 publications

References 78 publications

NO Generation from the Cross-Talks between Ene-diol Antioxidants and Nitrite at Metal Sites

NO Generation from the Cross-Talks between Ene-diol Antioxidants and Nitrite at Metal Sites

Nitrate and Nitrite Reductions at Copper(II) Sites: Role of Noncovalent Interactions from Second-Coordination-Sphere

An Integrated View of Nitrogen Oxyanion Deoxygenation in Solution Chemistry and Electrospray Ion Production

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