Phenol Reduces Nitrite to NO at Copper(II): Role of a Proton-Responsive Outer Coordination Sphere in Phenol Oxidation

Mondal, Aditesh; Reddy, Kiran P.; Bertke, Jeffery A.; Kundu, Subrata

doi:10.1021/jacs.9b11597

Cited by 27 publications

(68 citation statements)

References 37 publications

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“…By contrast, d-d transition bands of 1H-NO 2 include a maximum at 660 nm with two lower energy shoulders at 780 nm and 930 nm. The analogous d-d absorption features of 1-NO 2 are very similar to that of 1H-NO 2 but with minor differences in the relative intensities (Figure 4), which is attributed to the extent of the unsymmetrical nature of the k 2 -O,O' binding mode of nitrite as evident from the CuÀ O bond distances in the previously reported crystal structures [42] of 1-NO 2 and 1H-NO 2 (Table 1). The subtle differences in relative intensities of the d-d transition bands are indicative of different symmetry of the copper site.…”

Section: Complexsupporting

confidence: 68%

A Copper(II)‐Nitrite Complex Hydrogen‐Bonded to a Protonated Amine in the Second‐Coordination‐Sphere

et al. 2022

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Nitrous acid (HONO) plays pivotal roles in various metal‐free as well as metal‐mediated routes relevant to biogeochemistry, atmospheric chemistry, and mammalian physiology. While the metastable nature of HONO hinders the detailed investigations into its reactivity at a transition metal site, this report herein utilizes a heteroditopic copper(II) cryptate [oC]CuII featuring a proton‐responsive second‐coordination‐sphere located at a suitable distance from a [CuII](ONO) core, thereby enabling isolation of a [CuII](κ1‐ONO⋅⋅⋅H+) complex (2H‐NO2). A set of complementary analytical studies (UV‐vis, 14N/15N FTIR, 15N NMR, HRMS, EPR, and CHN) on 2H‐NO2 and its 15N‐isotopomer (2H‐15NO2) reveals the formulation of 2H‐NO2 as {[oCH]CuII(κ1‐ONO)}(ClO4)2. Non‐covalent interaction index (NCI) based on reduced density gradient (RDG) analysis on {[oCH]CuII(κ1‐ONO)}2+ discloses a H‐bonding interaction between the apical 3° ammonium site and the nitrite anion bound to the copper(II) site. The FTIR spectra of [CuII](κ1‐ONO⋅⋅⋅H+) species (2H‐NO2) shows a shift of ammonium NH vibrational feature to a lower wavenumber due to the H‐bonding interaction with nitrite. The reactivity profile of [CuII](κ1‐ONO⋅⋅⋅H+) species (2H‐NO2) towards anaerobic nitration of substituted phenol (2,4‐DTBP) is distinctly different relative to that of the closely related tripodal [CuII]‐nitrite complexes (1‐NO2/3‐NO2/4‐NO2).

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Section: Complexsupporting

confidence: 68%

A Copper(II)‐Nitrite Complex Hydrogen‐Bonded to a Protonated Amine in the Second‐Coordination‐Sphere

et al. 2022

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“…Then, the mixture was stirred and irradiated with 6 × 3 W blue LEDs (λ max = 450-465 nm) for 12 h. After the reaction completed, the solvent was removed under reduced pressure. The residue was purified by silica gel flash column chromatography to give cross-coupling products 5 a-g. Homo-coupling products 3,3',5,5'-tetra-tert-butyl-2,2'-biphenol (2 a): [20] mp 196-197 °C. According to the general procedure, purification via silica gel column chromatography (ethyl acetate/petroleum ether, 1/20) afforded a colorless solid.…”

Section: Methodsmentioning

confidence: 99%

“…3,3′,5,5′‐tetra‐tert‐butyl‐2,2′‐biphenol ( 2 a ): [20] mp 196–197 °C. According to the general procedure, purification via silica gel column chromatography (ethyl acetate/petroleum ether, 1/20) afforded a colorless solid.…”

Section: Methodsmentioning

confidence: 99%

Visible‐Light‐Driven di‐t‐Butyl Peroxide‐Promoted the Oxidative Homo‐ and Cross‐Coupling of Phenols

Jia

Yang

et al. 2022

Eur J Org Chem

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The visible-light-induced oxidative homo-and cross-coupling of phenols by di-t-butyl peroxide (DTBP) are described. These reactions occur with metal-free process and feature high chemo-and regioselectivity under mild reaction conditions. DTBP is an inexpensive, benign, stable at room temperature, and commercially available oxidizer. It can be irradiated by blue LEDs to generate tert-butoxyl radical ( t BuO•), which induces the oxidative homo-coupling of phenols and the cross-coupling of phenols with naphthols, respectively.

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“…Stimulated by the metalloenzyme active sites for nitrate and nitrite reductions, the previously reported strategies primarily employ transition‐metal‐based coordination complexes as the active site models [10–12] . For example, an iron(II) complex [N(afa Cy ) 3 Fe(OTf)](OTf) with amino‐azafulvene ligand arms has been shown to reduce both NO 3 − and NO 2 − to afford NO [10, 11a] .…”

Section: Figurementioning

confidence: 99%

Metal‐free Transformations of Nitrogen‐Oxyanions to Ammonia via Oxoammonium Salt

Sahana

Mondal

et al. 2021

Angew Chem Int Ed

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Transformations of nitrogen‐oxyanions (NOx−) to ammonia impart pivotal roles in sustainable biogeochemical processes. While metal‐mediated reductions of NOx− are relatively well known, this report illustrates proton‐assisted transformations of NOx− anions in the presence of electron‐rich aromatics such as 1,3,5‐trimethoxybenzene (TMB−H, 1 a) leading to the formation of diaryl oxoammonium salt [(TMB)2N+=O][NO3−] (2 a) via the intermediacy of nitrosonium cation (NO+). Detailed characterizations including UV/Vis, multinuclear NMR, FT‐IR, HRMS, X‐ray analyses on a set of closely related metastable diaryl oxoammonium [Ar2N+=O] species disclose unambiguous structural and spectroscopic signatures. Oxoammonium salt 2 a exhibits 2 e− oxidative reactivity in the presence of oxidizable substrates such as benzylamine, thiol, and ferrocene. Intriguingly, reaction of 2 a with water affords ammonia. Perhaps of broader significance, this work reveals a new metal‐free route germane to the conversion of NOx to NH3.

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Phenol Reduces Nitrite to NO at Copper(II): Role of a Proton-Responsive Outer Coordination Sphere in Phenol Oxidation

Cited by 27 publications

References 37 publications

A Copper(II)‐Nitrite Complex Hydrogen‐Bonded to a Protonated Amine in the Second‐Coordination‐Sphere

A Copper(II)‐Nitrite Complex Hydrogen‐Bonded to a Protonated Amine in the Second‐Coordination‐Sphere

Visible‐Light‐Driven di‐t‐Butyl Peroxide‐Promoted the Oxidative Homo‐ and Cross‐Coupling of Phenols

Metal‐free Transformations of Nitrogen‐Oxyanions to Ammonia via Oxoammonium Salt

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