An investigation on catalytic nitrite reduction reaction by bioinspired Cu<sup>II</sup> complexes

Chang, Yu‐Lun; Chen, Hsing-Yin; Chen, Sihong; Kao, Ching Huei; Michael, Y. Chiang; Hsu, Sodio C. N.

doi:10.1039/d1dt04102a

Cited by 8 publications

(9 citation statements)

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“…In contrast, a reaction of the nonheme-Fe II (dinitrite) complex with RSH affording disulfide (RSSR) and NO has been shown to proceed through an initial protonation of the nitrite moiety . Although the transformation of NO 2 – to NO at various redox-active transition metals such as Fe/Co/Ni/Cu has been relatively well explored in the presence of a diverse array of exogenous reductants (e.g., phosphine, CO, VCl 3 , thiol, phenol, and ene-diols), − the examples of analogous reactions at a redox-inactive [Zn II ] site and the underlying factors for promoting the reaction remain poorly understood. Notably, the NO-releasing reactions of [Zn II ]–nitrite complexes in the presence of external reductants like benzylthiol and 3,5-di- tert -butylcatechol have been reported to be slow. , Herein, this report investigates the thiol reactivity of a previously reported CA-model bound to nitrite, namely [( Bn 3 Tren )Zn II (κ 2 - O : O′ -nitrite)](ClO 4 ) ( 1 ) (Figure ), aiming to disclose biologically relevant conditions for an efficient transformation of nitrite-to-NO at a zinc(II) site.…”

Section: Introductionmentioning

confidence: 99%

NO Generation from Nitrite at Zinc(II): Role of Thiol Persulfidation in the Presence of Sulfane Sulfur

Sahana,

Valappil,

Amma

et al. 2023

ACS Org. Inorg. Au

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Nitrite-to-NO transformation is of prime importance due to its relevance in mammalian physiology. Although such a one-electron reductive transformation at various redox-active metal sites (e.g., Cu and Fe) has been illustrated previously, the reaction at the [Zn II ] site in the presence of a sacrificial reductant like thiol has been reported to be sluggish and poorly understood. Reactivity of [(Bn 3 Tren)Zn II −ONO](ClO 4 ) (1), a nitrite-bound model of the tripodal active site of carbonic anhydrase (CA), toward various organic probes, such as 4-tert-butylbenzylthiol ( t BuBnSH), 2,4-di-tert-butylphenol (2,4-DTBP), and 1-fluoro-2,4-dinitrobenzene (F-DNB), reveals that the ONO-moiety in the [Zn II ]−nitrite coordination motif of complex 1 acts as a mild electrophile. t BuBnSH reacts mildly with nitrite at a [Zn II ] site to provide S-nitrosothiol t BuBnSNO prior to the release of NO in 10% yield, whereas the phenolic substrate 2,4-DTBP does not yield the analogous O-nitrite compound (ArONO). The presence of sulfane sulfur (S 0 ) species such as elemental sulfur (S 8 ) and organic polysulfides ( t BuBnS n Bn t Bu) during the reaction of t BuBnSH and [Zn II ]−nitrite (1) assists the nitrite-to-NO conversion to provide NO yields of 65% (for S 8 ) and 76% (for t BuBnS n Bn t Bu). High-resolution mass spectrometry (HRMS) analyses on the reaction of [Zn II ]−nitrite (1), t BuBnSH, and S 8 depict the formation of zinc(II)-persulfide species [(Bn 3 Tren)Zn II −S n −Bn t Bu] + (where n = 2, 3, 4, 5, and 6). Trapping of the persulfide species ( t BuBnSS − ) with 1-fluoro-2,4-dinitrobenzene (F-DNB) confirms its intermediacy. The significantly higher nucleophilicity of persulfide species (relative to thiol/thiolate) is proposed to facilitate the reaction with the mildly electrophilic [Zn II ]−nitrite (1) complex. Complementary analyses, including multinuclear NMR, electrospray ionization-MS, UV−vis, and trapping of reactive S-species, provide mechanistic insights into the sulfane sulfur-assisted reactions between thiol and nitrite at the tripodal [Zn II ]-site. These findings suggest the critical influential roles of various reactive sulfur species, such as sulfane sulfur and persulfides, in the nitrite-to-NO conversion.

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Section: Introductionmentioning

confidence: 99%

NO Generation from Nitrite at Zinc(II): Role of Thiol Persulfidation in the Presence of Sulfane Sulfur

Sahana,

Valappil,

Amma

et al. 2023

ACS Org. Inorg. Au

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“…The reactivity of various Cu-(I) 20−30 and Cu(II) 22,26−29,31−41 model compounds with nitrite was investigated, and several Cu(II)−NO 27,42−44 and Cu(I)−NO 45−47 studies by Fujii and co-workers showed that a stepwise protonation mechanism is operative in dichloromethane, 23,25 and work by Hsu and co-workers sheds light on the possible formation of HNO 2 at low pH. 38 In recent years, bio-inspired CuNiRs are also studied using electrochemical methods in both organic 34,48,49 and aqueous solutions. 11−14,37,50−52 The first electrochemical studies on nitrite reduction were reported in 1993 and 1995 by the group of Komeda.…”

Section: ■ Introductionmentioning

confidence: 99%

“…The one-electron reduction of NO 2 – to NO is the second step of the denitrification process and occurs in the metalloenzyme nitrite reductase (NiR), containing either iron or copper in its active site. , In CuNiRs, reduction of NO 2 – takes place at a mononuclear type 2 Cu site (Figure a). , Inspired by the enzymatic process, nitrite reduction is studied using bio-inspired CuNiRs. The reactivity of various Cu(I) − and Cu(II) ,− ,− model compounds with nitrite was investigated, and several Cu(II)–NO ,− and Cu(I)–NO − complexes were characterized. In addition, studies by Fujii and co-workers showed that a stepwise protonation mechanism is operative in dichloromethane, , and work by Hsu and co-workers sheds light on the possible formation of HNO 2 at low pH …”

Section: Introductionmentioning

confidence: 99%

“…The reactivity of various Cu(I) − and Cu(II) ,− ,− model compounds with nitrite was investigated, and several Cu(II)–NO ,− and Cu(I)–NO − complexes were characterized. In addition, studies by Fujii and co-workers showed that a stepwise protonation mechanism is operative in dichloromethane, , and work by Hsu and co-workers sheds light on the possible formation of HNO 2 at low pH …”

Section: Introductionmentioning

confidence: 99%

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Elucidation of the Electrocatalytic Nitrite Reduction Mechanism by Bio-Inspired Copper Complexes

et al. 2023

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Mononuclear copper complexes relevant to the active site of copper nitrite reductases (CuNiRs) are known to be catalytically active for the reduction of nitrite. Yet, their catalytic mechanism has thus far not been resolved. Here, we provide a complete description of the electrocatalytic nitrite reduction mechanism of a bio-inspired CuNiR catalyst Cu(tmpa) (tmpa = tris(2-pyridylmethyl)amine) in aqueous solution. Through a combination of electrochemical studies, reaction kinetics, and density functional theory (DFT) computations, we show that the protonation steps take place in a stepwise manner and are decoupled from electron transfer. The rate-determining step is a general acid-catalyzed protonation of a copper-ligated nitrous acid (HNO 2 ) species. In view of the growing urge to convert nitrogencontaining compounds, this work provides principal reaction parameters for efficient electrochemical nitrite reduction. This contributes to the investigation and development of nitrite reduction catalysts, which is crucial to restore the biogeochemical nitrogen cycle.

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“…Several studies on the reduction of NO 2 – by Cu complexes have been reported. Spectroscopic studies and X-ray crystal structure determinations have revealed important aspects of NO 2 – reduction at Cu active centers. – Woollard-Shore et al reported the synthesis, characterization, and catalytic properties of four Cu(II) complexes as catalytic agents for NO 2 – reduction . Their crystallographic study revealed three different coordination modes: η 1 -NO 2 , η 1 -ONO, and η 2 -ONO.…”

Section: Introductionmentioning

confidence: 99%

Mechanistic Study of Reduction of Nitrite to NO by the Copper(II) Complex: Different Concerted Proton–Electron Transfer Reactivity between Nitrite and Nitro Complexes

Kametani,

Ikeda,

Yoshizawa

et al. 2023

Inorg. Chem.

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The literature contains numerous reports of copper complexes for nitrite (NO 2 − ) reduction. However, details of how protons and electrons arrive and how nitric oxide (NO) is released remain unknown. The influence of the coordination mode of nitrite on reactivity is also under debate. Kundu and co-workers have reported nitrite reduction by a copper(II) complex [J. Am. Chem. Soc. 2020, 142, 1726−1730. In their report, the copper(II) complex reduced nitrite using a phenol derivative as a reductant, resulting in NO, a hydroxyl copper(II) complex, and the corresponding biphenol. Also, the involvement of proton-coupled electron transfer was proposed by mechanistic studies. Herein, density functional theory calculations were performed to determine a mechanism for reduction of nitrite by a copper(II) complex. As a result of geometry optimization of an initial complex, two possible structures were obtained: Cu−ONO and Cu−NO 2 . Two possible reaction pathways initiated from Cu−ONO or Cu−NO 2 were then considered. The calculation results indicated that the Cu−ONO pathway is energetically favorable. When changes in the electronic structure were considered, both pathways were found to involve concerted proton−electron transfer (CPET). In addition, an intrinsic reaction coordinate analysis revealed that the two pathways were achieved by different types of CPET. Furthermore, an intrinsic bond orbital analysis clearly indicated that, in the Cu−ONO pathway, the chemical events involved proceeded concertedly yet asynchronously.

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An investigation on catalytic nitrite reduction reaction by bioinspired Cu^II complexes

Abstract: Catalytic nitrite reductions by CuII complexes containing anionic Me2Tp, neutral Me2Tpm, or neutral iPrTIC ligands in the presence of L-ascorbic acid, which served as an electron donor and proton source,...

Cited by 8 publications

References 53 publications

NO Generation from Nitrite at Zinc(II): Role of Thiol Persulfidation in the Presence of Sulfane Sulfur

NO Generation from Nitrite at Zinc(II): Role of Thiol Persulfidation in the Presence of Sulfane Sulfur

Elucidation of the Electrocatalytic Nitrite Reduction Mechanism by Bio-Inspired Copper Complexes

Mechanistic Study of Reduction of Nitrite to NO by the Copper(II) Complex: Different Concerted Proton–Electron Transfer Reactivity between Nitrite and Nitro Complexes

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An investigation on catalytic nitrite reduction reaction by bioinspired CuII complexes

Abstract: Catalytic nitrite reductions by CuII complexes containing anionic Me2Tp, neutral Me2Tpm, or neutral iPrTIC ligands in the presence of L-ascorbic acid, which served as an electron donor and proton source,...

Cited by 8 publications

References 53 publications

NO Generation from Nitrite at Zinc(II): Role of Thiol Persulfidation in the Presence of Sulfane Sulfur

NO Generation from Nitrite at Zinc(II): Role of Thiol Persulfidation in the Presence of Sulfane Sulfur

Elucidation of the Electrocatalytic Nitrite Reduction Mechanism by Bio-Inspired Copper Complexes

Mechanistic Study of Reduction of Nitrite to NO by the Copper(II) Complex: Different Concerted Proton–Electron Transfer Reactivity between Nitrite and Nitro Complexes

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An investigation on catalytic nitrite reduction reaction by bioinspired Cu^II complexes