Hexacoordinate Nickel(II)/(III) Complexes that Mimic the Catalytic Cycle of Nickel Superoxide Dismutase

Chatterjee, Sanjit; Maji, Ram Chandra; Barman, Suman K.; Olmstead, Marilyn M.; Patra, Apurba K.

doi:10.1002/anie.201404133

Cited by 26 publications

(17 citation statements)

References 49 publications

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“… 11 − 13 Over the past two decades, many high-valent metal complexes have been studied to gain fundamental insights into the structural, functional and mechanistic aspects of the enzymes and their counterparts. 14 − 17 Detailed mechanistic studies have shown that ET occurs through either inner-sphere or outer-sphere mechanisms and the M–O 2 •– species is an important reactive intermediate formed via the inner-sphere mechanism. 18 However, another class of effective inhibitors of ROS are antioxidants that are purely organic molecules.…”

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confidence: 99%

Perylene Diimide as a Precise Graphene-like Superoxide Dismutase Mimetic

Jalilov¹,

Nilewski²,

Berka

et al. 2017

ACS Nano

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Here we show that the active portion of a graphitic nanoparticle can be mimicked by a perylene diimide (PDI) to explain the otherwise elusive biological and electrocatalytic activity of the nanoparticle construct. Development of molecular analogues that mimic the antioxidant properties of oxidized graphenes, in this case the poly(ethylene glycolated) hydrophilic carbon clusters (PEG–HCCs), will afford important insights into the highly efficient activity of PEG–HCCs and their graphitic analogues. PEGylated perylene diimides (PEGn–PDI) serve as well-defined molecular analogues of PEG–HCCs and oxidized graphenes in general, and their antioxidant and superoxide dismutase-like (SOD-like) properties were studied. PEGn–PDIs have two reversible reduction peaks, which are more positive than the oxidation peak of superoxide (O2•–). This is similar to the reduction peak of the HCCs. Thus, as with PEG–HCCs, PEGn–PDIs are also strong single-electron oxidants of O2•–. Furthermore, reduced PEGn–PDI, PEGn–PDI•–, in the presence of protons, was shown to reduce O2•– to H2O2 to complete the catalytic cycle in this SOD analogue. The kinetics of the conversion of O2•– to O2 and H2O2 by PEG8–PDI was measured using freeze-trap EPR experiments to provide a turnover number of 133 s–1; the similarity in kinetics further supports that PEG8–PDI is a true SOD mimetic. Finally, PDIs can be used as catalysts in the electrochemical oxygen reduction reaction in water, which proceeds by a two-electron process with the production of H2O2, mimicking graphene oxide nanoparticles that are otherwise difficult to study spectroscopically.

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confidence: 99%

Perylene Diimide as a Precise Graphene-like Superoxide Dismutase Mimetic

Jalilov¹,

Nilewski²,

Berka

et al. 2017

ACS Nano

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“…Thee lectronic absorption spectrum of 1 Cl in CH 3 CN features bands at l max /nm (e/m À1 cm À1 ) = 912 (26), 550 sh (65), 323 (20 576), 294 (17 670) and 237 sh (32 750) comparable to those of reported octahedral Ni II complexes. [22][23][24] Thes low evaporation of aC H 3 CN/CH 2 Cl 2 solution of 1 Cl afforded crystals suitable for X-ray diffraction. TheX -ray structure of 1 Cl revealed it to be am onomer (Figure 1, top [23,24] but is % 0.07 longer than that of the MCR ox1-silent state of the enzyme where the Ni II has N 4 SO coordination and the Ni II -S CoM distance is 2.40 .…”

Section: Resultsmentioning

confidence: 99%

“…[22][23][24] Thes low evaporation of aC H 3 CN/CH 2 Cl 2 solution of 1 Cl afforded crystals suitable for X-ray diffraction. TheX -ray structure of 1 Cl revealed it to be am onomer (Figure 1, top [23,24] but is % 0.07 longer than that of the MCR ox1-silent state of the enzyme where the Ni II has N 4 SO coordination and the Ni II -S CoM distance is 2.40 . [25] TheS ÀSd istance of 1 Cl is in the range of typical SÀSd istances found with Ar-S-S-Ar disulfides.…”

Section: Resultsmentioning

confidence: 99%

“…As a continuing interest in understanding the donor strength dependent stabilization and reactivity of various Ni oxidation states (0, +1, +2 and +3) in an NS donor environment, herein, we report first the Ni‐mediated reversible thiolate/disulfide transformation. This study offers Ni II complexes, [(L S‐S )Ni(Cl)](ClO 4 ) ( 1 Cl ), [(L S‐S )Ni (Solvent)](ClO 4 ) 2 ( 1 Solv ), [Ni(L S ) 2 Ni(L S‐S) )](ClO 4 ) 2 ⋅0.5 Et 2 O ⋅1.5 H 2 O ( 2 ) and [Ni(L S ) 2 Ni(L S )](ClO 4 )⋅CH 3 CO 2 Et ( 3 ), derived from a tridentate N 2 S thiol donor ligand, HL S and its disulfide analogue, L S‐S (Scheme a).…”

Section: Introductionmentioning

confidence: 99%

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Nickel(II)‐Mediated Reversible Thiolate/Disulfide Conversion as a Mimic for a Key Step of the Catalytic Cycle of Methyl‐Coenzyme M Reductase

et al. 2020

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According to the well‐accepted mechanism, methyl‐coenzyme M reductase (MCR) involves Ni‐mediated thiolate‐to‐disulfide conversion that sustains its catalytic cycle of methane formation in the energy saving pathways of methanotrophic microbes. Model complexes that illustrate Ni‐ion mediated reversible thiolate/disulfide transformation are unknown. In this paper we report the synthesis, crystal structure, spectroscopic properties and redox interconversions of a set of NiII complexes comprising a tridentate N2S donor thiol and its analogous N4S2 donor disulfide ligands. These complexes demonstrate reversible NiII‐thiolate/NiII‐disulfide (both bound and unbound disulfide‐S to NiII) transformations via thiyl and disulfide monoradical anions that resemble a primary step of MCR's catalytic cycle.

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“…[46][47] The role of the fifth ligand in the axial position to stabilize the Ni III oxidation state has been also reproduced. 35,[41][42] However, the great majority of the low-molecular weight synthetic Ni II complexes, despite their apparent appropriate redox properties for SOD activity, are not active as catalysts even if they can mimic the partial [40][41] or full 48 catalytic cycle under stoichiometric conditions. Their lack of reactivity has often been rationalized either by their sensitivity to the superoxide or derivatives, or by the irreversibility of the Ni III /Ni II redox process.…”

Section: Scheme 1 Active and Catalysed Reaction Centre By The Nisodmentioning

confidence: 99%

Mononuclear Ni(II) Complexes with a S3O Coordination Sphere Based on a Tripodal Cysteine-Rich Ligand: pH Tuning of the Superoxide Dismutase Activity

et al. 2019

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The superoxyde dismutase (SOD) activity of mononuclear Ni II complexes, whose structures are inspired by the NiSOD, has been investigated. They have been designed with a sulfur-rich pseudo-peptide ligand, derived from nitrilotriacetic acid (NTA), where the three acid functions are grafted with cysteines (L 3S). Two mononuclear complexes, which exist in pH-dependent proportions, have been fully characterized by a combination of spectroscopic techniques including 1 H NMR, UV-vis, CD, and XAS, together with theoretical calculations. They display similar square-planar S3O coordination, with the three thiolates of the three cysteine moieties from L 3S coordinated to the Ni II ion, together with either a water molecule at physiological pH, as [NiL 3S (OH2)]-, or a hydroxo ion in more basic conditions, as [NiL 3S (OH)] 2-. The 1 H NMR study has revealed that contrary to the hydroxo ligand, the bound water molecule is labile. The CV of both complexes displays an irreversible one-electron oxidation process assigned to the Ni II /Ni III redox system with Epa = 0.48 and 0.31 V vs SCE for NiL 3S (OH2) and NiL 3S (OH), respectively. The SOD activity of both complexes has been tested. Based on the xanthine oxidase assay, an IC50 of about 1 µM has been measured at pH 7.4, where NiL 3S (OH2) is mainly present (93% of the Ni II species), while the IC50 is larger than 100 µM at pH 9.6, where NiL 3S (OH) is the major species (92% of the Ni II species). Interestingly, only NiL 3S (OH2) displays SOD activity, suggesting that the presence of a labile ligand is required. The SOD activity has been also evaluated under catalytic conditions at pH 7.75, where the ratio between NiL 3S (OH2) / NiL 3S (OH) is about (86:14), and a rate constant, kcat = 1.8 10 5 M-1 s-1 has been measured. NiL 3S (OH2) is thus the first low-molecular weight, synthetic, bio-inspired Ni complex that displays catalytic SOD activity in water at physiological pH, although it does not contain any N-donor ligand in its first coordination sphere, as in the NiSOD. Overall, the data evidences that a key structural feature is the presence of a labile ligand in the coordination sphere of the Ni II ion, consistent with an inner sphere mechanism for at least one of the redox reactions.

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Hexacoordinate Nickel(II)/(III) Complexes that Mimic the Catalytic Cycle of Nickel Superoxide Dismutase

Cited by 26 publications

References 49 publications

Perylene Diimide as a Precise Graphene-like Superoxide Dismutase Mimetic

Perylene Diimide as a Precise Graphene-like Superoxide Dismutase Mimetic

Nickel(II)‐Mediated Reversible Thiolate/Disulfide Conversion as a Mimic for a Key Step of the Catalytic Cycle of Methyl‐Coenzyme M Reductase

Mononuclear Ni(II) Complexes with a S3O Coordination Sphere Based on a Tripodal Cysteine-Rich Ligand: pH Tuning of the Superoxide Dismutase Activity

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