Resonance Raman spectra of molecular oxygen adducts of N,N'-ethylenebis(salicylideniminato)cobalt(II), [BCo(salen)]2O2 (B = pyridine, pyridine N-oxide, and dimethylformamide)

Nakamoto, K.; Suzuki, Masahiro; Ishiguro, Takeo; Kozuka, Muneteru; Nishida, Yoshihiro; Kida, Sigeo

doi:10.1021/ic50211a066

Cited by 19 publications

(5 citation statements)

References 3 publications

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“…This peak was absent in the IR spectra of the yellow and red decomposition products of the brown product as expected (data not shown). The value for V(02) of 854 cm-1 is in a frequency region expected for ,u-peroxo-dicobalt complexes (28), and it is between frequencies reported for the [pyCo(salen)]202 (salen = salicylideniminato; py = pyridine) complex (888 cm-') (29) and the [(NH3)5CO-(02)Co(NH3)5(NO3)4] complex (800 cm-') (30). It is significantly less than the Raman and IR 0-0 stretching frequencies reported for the ,u-superoxo-dicobalt(III) complexes (=1100 cm-') (31 (22) thermally stable (i.e., it did not release oxygen in the absence of light on the time scale of the experiment), a requirement for our future experiments with biological molecules.…”

Section: Methodssupporting

confidence: 57%

Photodissociation of a (mu-peroxo)(mu-hydroxo)bis[bis(bipyridyl)-cobalt(III)] complex: a tool to study fast biological reactions involving O2.

MacArthur

Sucheta²,

Chong³

et al. 1995

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

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Upon photolysis at 355 nm, dioxygen is released from a (-peroxo)(,-hydroxo)bis[bis(bipyridyl)cobalt- (III)] complex in aqueous solutions and at physiological pH with a quantum yield of 0.04. The [Co(bpy)2(H20)z2+ (bpy = bipyridyl) photoproduct was generated on a nanosecond or faster time scale as determined by time-resolved optical absorption spectroscopy. A linear correspondence between the spectral changes and the oxygen production indicates that 02 is released on the same time scale. Oxyhemoglobin was formed from deoxyhemoglobin upon photodissociation of the (,iperoxo)(,u-hydroxo)bis[bis(bipyridyl)cobalt(III)I complex, verifying that dioxygen is a primary photoproduct. This complex and other related compounds provide a method to study fast biological reactions involving 02, such as the reduction of dioxygen to water by cytochrome oxidase.Many biological reactions involving dioxygen are so fast that studies by conventional stopped-flow techniques are impractical. Initiation of these and other fast reactions by photolysis offers a different approach. For example, the reaction of cytochrome c oxidase with dioxygen can be studied by a flow-flash method in which the reaction is initiated upon photodissociation of carbon monoxide (CO) bound to cytochrome a3 (1, 2). However, this method is potentially compromised by the fate of the photodissociated CO and, therefore, may not represent the physiological reaction of the enzyme under turnover conditions (3, 4). It is also not applicable to nonheme oxygen-activating systems. An alternative involves 02 production in situ by photodissociating synthetic caged dioxygen carriers. An ideal system would involve a direct source of dioxygen that does not react prematurely with the protein of interest but would release oxygen upon photodissociation on any relevant time scale. There should be no electrochemical or chemical reactions of the dioxygen carrier and its photoproduct with the protein, and interference from the photoproduct in the spectral region of the protein should be negligible. High solubility in aqueous solutions at physiological pH and high oxygen quantum yield are also desirable.Synthetic caged dioxygen carriers such as dicobalt ,u-peroxoor ,u-superoxo-bridged derivatives have the potential to fulfill the above requirements. Many of these complexes are soluble in aqueous solutions and are amenable for study by various spectroscopic probes (5-7). The most extensively studied have been cobalt(II) complexes of polyamines (8-13), amino acids (8, 14-16), and dipeptide ligands (8, 15, (11,15,18). The hydroxo bridge has been proposed to "lock in" the peroxo bridge, thereby shifting the equilibrium toward the oxygenated species (18). An advantage of the ,u-peroxo and ,-superoxo cobalt complexes is that such complexes have their major absorbances in the UV region. Therefore, electronic transitions of the protein in the visible region can be investigated without serious interference from transitions due to the cobalt complexes.Several studies of the photochemical...

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Section: Methodssupporting

confidence: 57%

Photodissociation of a (mu-peroxo)(mu-hydroxo)bis[bis(bipyridyl)-cobalt(III)] complex: a tool to study fast biological reactions involving O2.

MacArthur

Sucheta²,

Chong³

et al. 1995

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

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“… − However, the vibrational frequencies of the metal–oxygen bond in metal superoxo or hydroperoxo compounds are reported to be in the 500 cm –1 region with small isotopic shifts, e.g., 12–21 cm –1 , upon 16 O/ 18 O substitution (Table S4, Supporting Information). ,,− For example, in a study reported by Bakac et al, the vibrational frequency of the Cr–O bond was observed at 503 cm –1 by measuring the resonance Raman spectrum of the η 1 -superoxochromium(III) complex, and interestingly, its isotopic shift was only 12 cm –1 upon 16 O/ 18 O substitution. It was proposed that significant coupling of the Cr–O stretch with other vibrational modes (e.g., the Cr–O–O bend) leads to the discrepancy between experiment and the calculation based on a diatomic oscillator model.…”

Section: Discussionmentioning

confidence: 99%

Water Oxidation by a Mononuclear Ruthenium Catalyst: Characterization of the Intermediates

et al. 2011

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A detailed characterization of intermediates in water oxidation catalyzed by a mononuclear Ru polypyridyl complex [Ru(II)-OH(2)](2+) (Ru = Ru complex with one 4-t-butyl-2,6-di-(1',8'-naphthyrid-2'-yl)-pyridine ligand and two 4-picoline ligands) has been carried out using electrochemistry, UV-vis and resonance Raman spectroscopy, pulse radiolysis, stopped flow, and electrospray ionization mass spectrometry (ESI-MS) with H(2)(18)O labeling experiments and theoretical calculations. The results reveal a number of intriguing properties of intermediates such as [Ru(IV)═O](2+) and [Ru(IV)-OO](2+). At pH > 2.9, two consecutive proton-coupled one-electron steps take place at the potential of the [Ru(III)-OH](2+)/[Ru(II)-OH(2)](2+) couple, which is equal to or higher than the potential of the [Ru(IV)═O](2+)/[Ru(III)-OH](2+) couple (i.e., the observation of a two-electron oxidation in cyclic voltammetry). At pH 1, the rate constant of the first one-electron oxidation by Ce(IV) is k(1) = 2 × 10(4) M(-1) s(-1). While pH-independent oxidation of [Ru(IV)═O](2+) takes place at 1420 mV vs NHE, bulk electrolysis of [Ru(II)-OH(2)](2+) at 1260 mV vs NHE at pH 1 (0.1 M triflic acid) and 1150 mV at pH 6 (10 mM sodium phosphate) yielded a red colored solution with a Coulomb count corresponding to a net four-electron oxidation. ESI-MS with labeling experiments clearly indicates that this species has an O-O bond. This species required an additional oxidation to liberate an oxygen molecule, and without any additional oxidant it completely decomposed slowly to form [Ru(II)-OOH](+) over 2 weeks. While there remains some conflicting evidence, we have assigned this species as (1)[Ru(IV)-η(2)-OO](2+) based on our electrochemical, spectroscopic, and theoretical observations alongside a previously reported analysis by T. J. Meyer's group (J. Am. Chem. Soc. 2010, 132, 1545-1557).

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“…Relevant to this consideration is the ν O–O at 1011 cm –1 that was observed in the Raman spectrum of solid oxygenated Co(salen) of the phase that we deduce from the reported preparation was 12 . 58 It is pertinent to compare this value to the ν O–O stretches in the solid-state peroxide-bridged dicobalt complexes {[(NH 3 ) 5 Co] 2 (μ 2 -O 2 )}(SO 4 ) 2 , 59 {[Co(salen)DMF] 2 (μ 2 -O 2 )}, 58 , 60 oxymyoglobin, 61 and Co( TPP )superoxide, 62 which appear at 808, 897, 1103, and 1287 cm –1 , respectively. This is therefore consistent with the bound O 2 in 12 , showing a tendency toward superoxide character.…”

Section: Resultsmentioning

confidence: 99%

“…The lattice structure of 10 may be important for preventing collapse of the channels created on the desorption of the pyridine. Although the orientation of the Co(salen) units is close to ideal for the incorporation of an anti-μ 2 -peroxide ligand, the interatomic Co 58,60 oxymyoglobin, 61 and Co(TPP)superoxide, 62 which appear at 808, 897, 1103, and 1287 cm −1 , respectively. This is therefore consistent with the bound O 2 in 12, showing a tendency toward superoxide character.…”

Section: Class I O 2 Active Phases: γ- δ- and ε-Co(salen)mentioning

confidence: 99%

Structure Activity Relationships for Reversible O₂ Chemisorption by the Solid Phases of Co(salen) and Co(3F-salen)

Møller

McKenzie

2023

JACS Au

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The potential of solid-state materials comprising Co(salen) units for concentrating dioxygen from air was recognized over 80 years ago. While the chemisorptive mechanism at the molecular level is largely understood, the bulk crystalline phase plays important, yet unidentified roles. We have reverse crystal-engineered these materials and can for the first time describe the nanostructuring requisite for achieving reversible O2 chemisorption by Co(3R-salen) R = H or F, the simplest and most effective of the many known derivatives of Co(salen). Of the six phases of Co(salen) identified, α-ζ: α = ESACIO, β = VEXLIU, γ, δ, ε, and ζ (this work), only γ, δ, ε, and ζ are capable of reversible O2 binding. Class I materials (phases γ, δ, and ε) are obtained by desorption (40–80 °C, atmospheric pressure) of the co-crystallized solvent from Co(salen)·(solv), solv = CHCl3, CH2Cl2, or 1.5 C6H6. The oxy forms comprise between 1:5 and 1:3 O2:[Co] stoichiometries. Class II materials achieve an apparent maximum of 1:2 O2:Co(salen) stoichiometries. The precursors for the Class II materials comprise [Co(3R-salen)(L)·(H2O) x ], R = H, L = pyridine, and x = 0; R = F, L = H2O, and x = 0; R = F, L = pyridine, and x = 0; R = F, L = piperidine, and x = 1. Activation of these depends on the desorption of the apical ligand (L) that templates channels through the crystalline compounds with the Co(3R-salen) molecules interlocked in a Flemish bond brick pattern. The 3F-salen system produces F-lined channels proposed to facilitate O2 transport through the materials through repulsive interactions with the guest O2. We postulate that a moisture dependence of the activity of the Co(3F-salen) series is due to a highly specific binding pocket for locking in water via bifurcated hydrogen bonding to the two coordinated phenolato O atoms and the two ortho F atoms.

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Resonance Raman spectra of molecular oxygen adducts of N,N'-ethylenebis(salicylideniminato)cobalt(II), [BCo(salen)]2O2 (B = pyridine, pyridine N-oxide, and dimethylformamide)

Cited by 19 publications

References 3 publications

Photodissociation of a (mu-peroxo)(mu-hydroxo)bis[bis(bipyridyl)-cobalt(III)] complex: a tool to study fast biological reactions involving O2.

Photodissociation of a (mu-peroxo)(mu-hydroxo)bis[bis(bipyridyl)-cobalt(III)] complex: a tool to study fast biological reactions involving O2.

Water Oxidation by a Mononuclear Ruthenium Catalyst: Characterization of the Intermediates

Structure Activity Relationships for Reversible O₂ Chemisorption by the Solid Phases of Co(salen) and Co(3F-salen)

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Resonance Raman spectra of molecular oxygen adducts of N,N'-ethylenebis(salicylideniminato)cobalt(II), [BCo(salen)]2O2 (B = pyridine, pyridine N-oxide, and dimethylformamide)

Cited by 19 publications

References 3 publications

Photodissociation of a (mu-peroxo)(mu-hydroxo)bis[bis(bipyridyl)-cobalt(III)] complex: a tool to study fast biological reactions involving O2.

Photodissociation of a (mu-peroxo)(mu-hydroxo)bis[bis(bipyridyl)-cobalt(III)] complex: a tool to study fast biological reactions involving O2.

Water Oxidation by a Mononuclear Ruthenium Catalyst: Characterization of the Intermediates

Structure Activity Relationships for Reversible O2 Chemisorption by the Solid Phases of Co(salen) and Co(3F-salen)

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Product

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Structure Activity Relationships for Reversible O₂ Chemisorption by the Solid Phases of Co(salen) and Co(3F-salen)