Electrochemical Properties and Reactivity Study of [Mn<sup>V</sup>(O)(μ-OR–Lewis Acid)] Cores

Gupta, Geetika; Bera, Moumita; Paul, S.; Paria, Sayantan

doi:10.1021/acs.inorgchem.1c02601

Cited by 13 publications

(16 citation statements)

References 78 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A Δ S ‡ value of −23 and ca. −20 cal K –1 mol –1 has been reported for a HAT reaction between Ru IV O or Mn V O and BNAH, respectively. In the occurrence of a hydride atom transfer pathway, a more negative Δ S ‡ value would be expected because of the formation of a more ordered transition state, as reported for the oxidation of 2-propanol .…”

Section: Resultsmentioning

confidence: 97%

Structural and Spectroscopic Characterization of Copper(III) Complexes and Subsequent One-Electron Oxidation Reaction and Reactivity Studies

et al. 2023

Self Cite

View full text Add to dashboard Cite

The formation of Cu(III) species are often invoked as the key intermediate in Cu-catalyzed organic transformation reactions. In this study, we synthesized Cu(II) (1) and Cu(III) (3) complexes supported by a bisamidate−bisalkoxide ligand consisting of an ortho-phenylenediamine (o-PDA) scaffold and characterized them through an array of spectroscopic techniques, including UV−visible, electron paramagnetic resonance, X-ray crystallography, and 1 H nuclear magnetic resonance (NMR) and X-ray absorption spectroscopy. The Cu−N/O bond distances in 3 are ∼0.1 Å reduced compared to 1, implying a significant increase in 3's overall effective nuclear charge. Further, a Cu(III) complex (4) of a bisamidate−bisalkoxide ligand containing a transcyclohexane-1,2-diamine moiety exhibits nearly identical Cu−N/O bond distances to that of 3, inferring that the redox-active o-PDA backbone is not oxidized upon one-electron oxidation of the Cu(II) complex (1). In addition, a considerable difference in the 1s → 4p and 1s → 3d transition energy was observed in the X-ray absorption near-edge structure data of 3 vs 1, which is typical for the metal-centered oxidation process. Electrochemical measurements of the Cu(II) complex (1) in acetonitrile exhibited two consecutive redox couples at −0.9 and 0.4 V vs the Fc + /Fc reference electrode. One-electron oxidation reaction of 3 further resulted in the formation of a ligand-oxidized Cu complex (3a), which was characterized in depth. Reactivity studies of species 3 and 3a were explored toward the activation of the C−H/O−H bonds. A bond dissociation free energy (BDFE) value of ∼69 kcal/mol was estimated for the O−H bond of the Cu(II) complex formed upon transfer of hydrogen atom to 3. The study represents a thorough spectroscopic characterization of high-valent Cu complexes and sheds light on the PCET reactivity studies of Cu(III) complexes.

show abstract

Section: Resultsmentioning

confidence: 97%

Structural and Spectroscopic Characterization of Copper(III) Complexes and Subsequent One-Electron Oxidation Reaction and Reactivity Studies

et al. 2023

Self Cite

View full text Add to dashboard Cite

show abstract

“…A crystal structure of a mononuclear manganese(V)-oxo complex, [(HMPAB)Mn V (O)] − (H 4 HMPAB = 1,2-bis(2-hydroxy-2-methylpropanamido)benzene), revealed that a Mn–O term distance is 1.566(4) Å as shown in Figure . The reaction of [(HMPAB)Mn V (O)] − with redox-inactive metal ions (M n + = Li + , Ca 2+ , Mg 2+ , Y 3+ , and Sc 3+ ) resulted in the formation of [(HMPAB)Mn V (O)] − -M n + adducts, which were characterized by UV–vis, 1 H NMR, cyclic voltammetry, and in situ IR spectroscopy . Theoretical calculations suggested that the alkoxide oxygen atoms in the ligand scaffold are the most energetically favorable for coordinating the M n + ion at [(HMPAB)Mn V (O)] − (Figure ).…”

Section: Metal-oxygen Intermediatesmentioning

confidence: 99%

“…X-ray crystal structure of [(HMPAB)Mn V (O)] − , showing the binding mode of metal ions (M n + ) confirmed by DFT caculations …”

Section: Metal-oxygen Intermediatesmentioning

confidence: 99%

Reaction Intermediates in Artificial Photosynthesis with Molecular Catalysts

et al. 2022

View full text Add to dashboard Cite

In nature, water oxidation is catalyzed by Mn4Ca clusters in the oxygen-evolving complex (OEC) of photosystem II (PSII), in which a manganese(V)-oxo species acts as an active reaction intermediate. Electrons and protons taken from water in PSII are used to reduce plastoquinone to plastoquinol via photoinduced charge separation in the photosynthetic reaction center. In photosystem I (PSI), NADP+ coenzyme is reduced by plastoquinol via photoinduced charge separation in the photosynthetic reaction center to produce NADPH, which is used as a reductant to reduce CO2 to carbohydrates in the Calvin cycle. Extensive efforts have so far been made to mimic functions of PSII and PSI for photocatalytic water oxidation and reduction to produce O2 and H2, respectively. Characterization and reactivity of high-valent metal-oxo, -hydroperoxo, -peroxo, and -superoxo intermediates have been investigated to clarify the mechanisms of water oxidation. Metal hydride complexes have also been studied in relation with the catalytic reactivity for water reduction to produce H2 as well as NAD+ reduction to NADH. This Review is intended to provide an overview on the functional model reactions of PSII and PSI for the photocatalytic water oxidation and reduction, respectively. The roles of high-valent metal-oxo, -hydroperoxo, -peroxo, and -superoxo complexes as the reaction intermediates in photocatalytic water oxidation are focused in relation with the catalytic mechanisms of water oxidation. The roles of metal hydride complexes are also discussed in relation with the catalytic mechanisms of hydrogen evolution and NAD+ reduction to NADH. The combination of functional model reactions of PSII and PSI leads to construct molecular artificial photosynthetic systems in which water is split to H2 and O2 in a 2:1 ratio, providing a way to realize artificial photosynthesis in molecular levels.

show abstract

“…However, those studies are scarce and explored in a limited number of examples. ,− Recently, we examined the electrocatalytic WO reaction by molecular copper complexes supported by redox-active bis-amidate-bis-alkoxide ligands (L 1 and L 2 ) . We also noted that the ligand system (Chart ) is suitable for stabilizing metastable reaction intermediates for spectroscopic interrogation. − In this study, we set out to explore the electrocatalytic WO activity of Co complexes supported by L 1 and L 2 and characterize the reaction intermediates involved in the WO reaction. Here, we report the electrocatalytic WO by molecular Co complexes, [Co(L 1 )] − ( 1 ) and [Co(L 2 )] − ( 2 ), in 0.1 M phosphate buffer solution (PBS) at pH 8.0 and in acetonitrile.…”

Section: Introductionmentioning

confidence: 99%

Characterization of Reaction Intermediates Involved in the Water Oxidation Reaction of a Molecular Cobalt Complex

et al. 2022

Self Cite

View full text Add to dashboard Cite

Molecular cobalt(III) complexes of bis-amidate-bis-alkoxide ligands, (Me4N)[CoIII(L1)] (1) and (Me4N)[CoIII(L2)] (2), are synthesized and assessed through a range of characterization techniques. Electrocatalytic water oxidation activity of the Co complexes in a 0.1 M phosphate buffer solution revealed a ligand-centered 2e–/1H+ transfer event at 0.99 V followed by catalytic water oxidation (WO) at an onset overpotential of 450 mV. By contrast, 2 reveals a ligand-based oxidation event at 0.9 V and a WO onset overpotential of 430 mV. Constant potential electrolysis study and rinse test experiments confirm the homogeneous nature of the Co complexes during WO. The mechanistic investigation further shows a pH-dependent change in the reaction pathway. On the one hand, below pH 7.5, two consecutive ligand-based oxidation events result in the formation of a CoIII(L2–)(OH) species, which, followed by a proton-coupled electron transfer reaction, generates a CoIV(L2–)(O) species that undergoes water nucleophilic attack to form the O–O bond. On the other hand, at higher pH, two ligand-based oxidation processes merge together and result in the formation of a CoIII(L2–)(OH) complex, which reacts with OH– to yield the O–O bond. The ligand-coordinated reaction intermediates involved in the WO reaction are thoroughly studied through an array of spectroscopic techniques, including UV–vis absorption spectroscopy, electron paramagnetic resonance, and X-ray absorption spectroscopy. A mononuclear CoIII(OH) complex supported by the one-electron oxidized ligand, [CoIII(L3–)(OH)]−, a formal CoIV(OH) complex, has been characterized, and the compound was shown to participate in the hydroxide rebound reaction, which is a functional mimic of Compound II of Cytochrome P450.

show abstract

Electrochemical Properties and Reactivity Study of [Mn^V(O)(μ-OR–Lewis Acid)] Cores

Cited by 13 publications

References 78 publications

Structural and Spectroscopic Characterization of Copper(III) Complexes and Subsequent One-Electron Oxidation Reaction and Reactivity Studies

Structural and Spectroscopic Characterization of Copper(III) Complexes and Subsequent One-Electron Oxidation Reaction and Reactivity Studies

Reaction Intermediates in Artificial Photosynthesis with Molecular Catalysts

Characterization of Reaction Intermediates Involved in the Water Oxidation Reaction of a Molecular Cobalt Complex

Contact Info

Product

Resources

About

Electrochemical Properties and Reactivity Study of [MnV(O)(μ-OR–Lewis Acid)] Cores

Cited by 13 publications

References 78 publications

Structural and Spectroscopic Characterization of Copper(III) Complexes and Subsequent One-Electron Oxidation Reaction and Reactivity Studies

Structural and Spectroscopic Characterization of Copper(III) Complexes and Subsequent One-Electron Oxidation Reaction and Reactivity Studies

Reaction Intermediates in Artificial Photosynthesis with Molecular Catalysts

Characterization of Reaction Intermediates Involved in the Water Oxidation Reaction of a Molecular Cobalt Complex

Contact Info

Product

Resources

About

Electrochemical Properties and Reactivity Study of [Mn^V(O)(μ-OR–Lewis Acid)] Cores