Synthesis, characterization, and reactivity of oxomanganese(IV) porphyrin complexes

Groves, John T.; Stern, Michael

doi:10.1021/ja00234a009

Cited by 288 publications

(154 citation statements)

References 1 publication

Supporting

Mentioning

141

Contrasting

Unclassified

Order By: Relevance

“…2g). The great change of the l max (from 477 to 430 nm) indicated the change of the oxidation state of metal and known synthetic high-valent manganese-oxo porphyrins have l max in the range of 420 to 450 nm 6,10 . In addition, Newcomb et al 12 54 .…”

Section: Discussionmentioning

confidence: 99%

“…It exhibits promising catalytic behaviour for a host of oxidative reactions, and so a primary goal of cytochrome P450 research is in the application of these enzymes, or their derivatives, in catalytic oxidation of unactivated C-H bonds, such as the hydroxylation of cyclohexane. Many synthetic metalloporphyrin model compounds have been synthesized to probe the mechanisms of the behaviours of cytochrome P450 oxygenases [3][4][5][6][7][8][9][10][11][12][13] , but the detailed pathways are still elusive, especially for the steps involving highly reactive intermediates. For a long time, it has been believed that oxoiron (IV) porphyrin p-cation radical (named as Compound I) is the unique reactive intermediate in cytochrome P450 catalysed oxidative reactions (Fig.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Spectroscopic observation of iodosylarene metalloporphyrin adducts and manganese(V)-oxo porphyrin species in a cytochrome P450 analogue

Guo

Dong

et al. 2012

Nat Commun

View full text Add to dashboard Cite

Different metalloporphyrin model compounds have been synthesized to study the mechanisms of cytochrome P450s with various terminal oxidants, and numerous intermediates have been reported. However, the detailed mechanism of the oxygen atom transfer from iodosylarene to the substrates remains unclear. Here we report the direct ultraviolet-visible spectroscopic observation of the soluble iodosylarene-manganese porphyrin adduct following catalytic oxidation using 2,4,6-tri-tert-butylphenol as the reductant. When the reductant is changed to cisstilbene, the rate-determining step also changes. Both the iodosylarene-manganese porphyrin adduct and [(porphyrin)Mn(V) ¼ O] species may be simultaneously observed. In the absence of reductant, the adduct of iodosylarene with sterically hindered [Mn(meso-tetrakis(2,6-dichlorophenyl)porphinato)Cl] is immediately formed, and smoothly converted into a highvalent [(porpyrinato)Mn ¼ O]. Electrospray ionization mass spectrometry analysis of the reaction further confirms the transformation between these species. This study provides an insight into the mechanism of oxygen transfer within the haem-containing enzymatic systems.

show abstract

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Spectroscopic observation of iodosylarene metalloporphyrin adducts and manganese(V)-oxo porphyrin species in a cytochrome P450 analogue

Guo

Dong

et al. 2012

Nat Commun

View full text Add to dashboard Cite

show abstract

“…An alternative approach to exploring possible intermediates in O−O bond formation is to develop synthetic systems with Mn-oxo species and investigate spectroscopically whether they support either a Mn V -oxo state or a Mn IV -oxyl state (16)(17)(18). We have thus prepared a series of monomeric Mn-oxo complexes [Mn n H 3 buea(O)] m (n = 3+ to 5+; m = 2− to 0) in which [H 3 buea] 3− provides a strong anionic ligand field while maintaining local C 3 symmetry around the manganese centers ( Fig.…”

Section: IIImentioning

confidence: 99%

High-spin Mn–oxo complexes and their relevance to the oxygen-evolving complex within photosystem II

Gupta

Taguchi

Lassalle‐Kaiser

et al. 2015

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

134

162

View full text Add to dashboard Cite

The structural and electronic properties of a series of manganese complexes with terminal oxido ligands are described. The complexes span three different oxidation states at the manganese center (III-V), have similar molecular structures, and contain intramolecular hydrogen-bonding networks surrounding the Mn-oxo unit. Structural studies using X-ray absorption methods indicated that each complex is mononuclear and that oxidation occurs at the manganese centers, which is also supported by electron paramagnetic resonance (EPR) studies. This gives a high-spin Mn V -oxo complex and not a Mn IV -oxy radical as the most oxidized species. In addition, the EPR findings demonstrated that the Fermi contact term could experimentally substantiate the oxidation states at the manganese centers and the covalency in the metal-ligand bonding. Oxygen-17-labeled samples were used to determine spin density within the Mn-oxo unit, with the greatest delocalization occurring within the Mn V -oxo species (0.45 spins on the oxido ligand). The experimental results coupled with density functional theory studies show a large amount of covalency within the Mn-oxo bonds. Finally, these results are examined within the context of possible mechanisms associated with photosynthetic water oxidation; specifically, the possible identity of the proposed high valent Mn-oxo species that is postulated to form during turnover is discussed.metal-oxo complexes | water oxidation | inorganic chemistry | photosynthesis | oxygen-evolving complex P hotosynthetic water oxidation is an essential chemical reaction that is responsible for producing Earth's aerobic environment. Dioxygen production occurs at the active site of the enzyme photosystem II, referred to as the oxygen-evolving complex (OEC), which contains a unique Mn 4 CaO cluster (1, 2). Several features of the OEC are known, including an approximate arrangement of the metal ions within the cluster (Fig. 1A) (3, 4), its structural flexibility during turnover (5, 6), and its ability to store oxidizing equivalents via five photo-induced redox states (S i , i = 0-4 and known as the Kok cycle) (7). Substrate water molecules bind to the cluster and, upon oxidation, are coupled to produce dioxygen and 4 eq of protons. There is agreement that formation of the O-O bond occurs in the highest oxidized state of the Mn 4 CaO 5 cluster (S 4 ), after which the cluster reverts to the most reduced state, S 0 (1-6, 8-10). The transient S 4 state has eluded detection, making it difficult to experimentally probe the structural and physical requirements necessary to promote dioxygen production. Magnetic resonance and density functional theory (DFT) studies of the S 2 and S 3 states have been used to infer that the beginning and ending oxidation states of the Kok cycle are Mn 3 III Mn IV (S 0 ) and Mn 3 IV Mn V or Mn 3 IV Mn IV O • (S 4 ) (11-14). The location of the Mn V center within the cluster is not certain, yet one possibility is the dangling Mn A4 site, which is coordinated to anionic donors and is surrounded by a ne...

show abstract

“…Here we extend this work into the domain of chemically active metalloporphyrins that are known to catalyze oxygen transfer reactions in solution. [14][15][16][17][18][19][20][21] As explained above, this is the next step towards the creation of hybrid heterogeneous selective oxidation catalysts. Our aim was to deposit the acetyl-protected porphyrin [SAc] 4 P-Mn(III)Cl ( Figure 1) on Ag(100), deprotect it by removal of the acetyl groups thus enabling covalent tethering to the surface by Ag-S bonds, and finally activate it by removal of the axial chlorine ligand.…”

Section: Introductionmentioning

confidence: 99%

“…In regard to their homogenous chemistry, manganese porphyrins are well known for their effectiveness as selective oxidation catalysts when used in conjunction with a single-oxygen donor. [14][15][16][17][18][19][20][21] In the present case, the silver surface bearing oxygen adatoms is envisaged as the entity that will act the single oxygen donor. Temperature programmed desorption experiments were conducted in Cambridge in an ultra-high vacuum chamber operated at a base pressure of 1×10 -10 torr.…”

Section: Introductionmentioning

confidence: 99%

Deprotection, Tethering, and Activation of a Catalytically Active Metalloporphyrin to a Chemically Active Metal Surface: [SAc]₄P−Mn(III)Cl on Ag(100)

et al. 2009

View full text Add to dashboard Cite

The adsorption and subsequent thermal chemistry of the acetyl-protected manganese porphyrin,[SAc] 4 P-Mn(III)Cl on Ag(100) have been studied by high resolution XPS and temperature programmed desorption. The de-protection event, leading to formation of the covalently bound thio-porphyrin, has been characterized and the conditions necessary for removal of the axial chlorine ligand have been determined, thus establishing a methodology for creating tethered activated species that could serve as catalytic sites for delicate oxidation reactions. Surface-mediated acetyl deprotection occurs at 298 K, at which temperature porphyrin diffusion is limited. At temperatures above ~ 425 K porphyrin desorption, diffusion and deprotection occur and at > 470 K axial chlorine ligand is removed.

show abstract

Synthesis, characterization, and reactivity of oxomanganese(IV) porphyrin complexes

Cited by 288 publications

References 1 publication

Spectroscopic observation of iodosylarene metalloporphyrin adducts and manganese(V)-oxo porphyrin species in a cytochrome P450 analogue

Spectroscopic observation of iodosylarene metalloporphyrin adducts and manganese(V)-oxo porphyrin species in a cytochrome P450 analogue

High-spin Mn–oxo complexes and their relevance to the oxygen-evolving complex within photosystem II

Deprotection, Tethering, and Activation of a Catalytically Active Metalloporphyrin to a Chemically Active Metal Surface: [SAc]₄P−Mn(III)Cl on Ag(100)

Contact Info

Product

Resources

About

Synthesis, characterization, and reactivity of oxomanganese(IV) porphyrin complexes

Cited by 288 publications

References 1 publication

Spectroscopic observation of iodosylarene metalloporphyrin adducts and manganese(V)-oxo porphyrin species in a cytochrome P450 analogue

Spectroscopic observation of iodosylarene metalloporphyrin adducts and manganese(V)-oxo porphyrin species in a cytochrome P450 analogue

High-spin Mn–oxo complexes and their relevance to the oxygen-evolving complex within photosystem II

Deprotection, Tethering, and Activation of a Catalytically Active Metalloporphyrin to a Chemically Active Metal Surface: [SAc]4P−Mn(III)Cl on Ag(100)

Contact Info

Product

Resources

About

Deprotection, Tethering, and Activation of a Catalytically Active Metalloporphyrin to a Chemically Active Metal Surface: [SAc]₄P−Mn(III)Cl on Ag(100)