Isolation, purification, and characterization of intermediate (iodosylbenzene)metalloporphyrin complexes from the (tetraphenylporphinato)manganese(III)-iodosylbenzene catalytic hydrocarbon functionalization system

Smegal, John A.; Schardt, Bruce C.; Hill, Craig L.

doi:10.1021/ja00349a024

Cited by 125 publications

(58 citation statements)

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“…As shown in Table S . [19,20] The reaction was found to be zero order with respect to the terminal oxidant (Table S-4, Supporting Information). This implies that the formation of the active oxidant cannot be rate-determining.…”

Section: Saturation Kineticsmentioning

confidence: 99%

Kinetics of (Porphyrin)manganese(III)‐Catalyzed Olefin Epoxidation with a Soluble Iodosylbenzene Derivative

et al. 2006

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We examined the kinetics of a well-behaved system for homogeneous porphyrin-catalyzed olefin epoxidation with a soluble iodosylbenzene derivative 1 as the terminal oxidant and Mn(TPFPP)Cl (2) as the catalyst. The epoxidation rates were measured by using the initial rate method, and the epoxidation products were determined by gas chromatography. The epoxidation rate was found to be first order with respect to the porphyrin catalyst and zero order on the terminal oxidant. In addition, we found the rate law to be sensitive to the nature and concentration of olefin substrates. Saturation kinetics were observed with all olefin substrates at high olefin concentrations, and the kinetic data are consistent with a Michaelis-Menten kinetic model. According to the observed saturation kinetic results, we propose that there is a complexation between the active oxidant and the substrate, and the rate-determining step is thought to be the breakdown of this putative substrate-oxidant complex that

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Section: Saturation Kineticsmentioning

confidence: 99%

Kinetics of (Porphyrin)manganese(III)‐Catalyzed Olefin Epoxidation with a Soluble Iodosylbenzene Derivative

et al. 2006

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“…An overview of the possible reaction pathways involving manganese porphyrins and oxygen, based on the literature [1][2][3]18,[20][21][22][23][24][25][26][27][28][29] and the observations described here, is depicted in Figure 1. A reduction of the manganese centre of the porphyrin from Mn(III) to Mn(II) with loss of the counterion 20 is a requirement for the binding of an oxygen molecule to give a dioxygen adduct 21 .…”

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confidence: 99%

“…Subsequently, the oxygen-oxygen bond of the resulting species can be cleaved following two possible pathways: (i) a reaction with Mn(II) to form two Mn(IV)-oxo complexes 18,22,23 ; (ii) a reaction with an electron and two protons to generate water and a [Mn(V)-oxo] + species [1][2][3] . The Mn(IV)-oxo species is active in the epoxidation of alkenes 3,24 , and in the absence of such substrates it can connect to an additional Mn(II) porphyrin to give a µ-oxo bridged Mn(III) dimer [25][26][27][28] In a first experiment we deposited a droplet of a ~10 −5 M solution of Mn1Cl in 1-octanoic acid at the basal plane of a freshly cleaved highly oriented pyrolytic graphite (HOPG) sample under ambient conditions. Related alkyl-functionalised free base porphyrin molecules are known to form well-ordered monolayers on the same substrate 30,31 .…”

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confidence: 99%

Detection of different oxidation states of individual manganese porphyrins during their reaction with oxygen at a solid/liquid interface

et al. 2013

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[4][5][6][7] . The majority of these studies use ensemble techniques in solution, such as electrochemistry and absorption, electron paramagnetic resonance and nuclear magnetic resonance spectroscopy. The scanning tunneling microscope (STM) has proven to be a promising tool to study reactions at the molecular level [8][9][10][11][12] , and initial experiments have been reported in which the reactive properties of metal porphyrins were studied on a surface at the single molecule level by STM in ultrahigh vacuum (UHV) [13][14][15][16][17] and under ambient conditions 18,19 .Here we report detailed STM studies of the complex redox chemistry of reactions between 10,15,R,R,porphyrin manganese(III) chloride (Mn1Cl, Fig. 2a) and different oxygen donors at a solid/liquid interface. Although the dynamic nature of the molecules at this interface complicates the use of techniques that are typically being used under UHV conditions, such as X-ray 3 Photoelectron Spectroscopy (XPS), STM can provide extremely high spatial resolution and insight into changes in the electronic properties of molecules with a liquid medium over them.These liquid conditions make the system far more comparable with processes taking place in biological systems than the UHV conditions, where solvent-mediated factors such as the diffusion and concentration of reactants are fully absent. It is in principle possible with STM to monitor single molecules at the highest detail while they are involved in multistep chemical reactions with STM, and to image and identify reactants, intermediates and products in the most direct way, i.e. by imaging. This approach allows the study of reaction dynamics in realspace and real-time, which may provide unique information about reaction mechanisms that remains hidden in ensemble measurements at the macroscopic scale. STM may reveal variations in reactivity of single molecules, the relation of these variations to molecular adsorption geometry, and cooperativity effects at the nanometre scale.An overview of the possible reaction pathways involving manganese porphyrins and oxygen, based on the literature 1-3,18,20-29 and the observations described here, is depicted in Figure 1 In a first experiment we deposited a droplet of a ~10 −5 M solution of Mn1Cl in 1-octanoic acid at the basal plane of a freshly cleaved highly oriented pyrolytic graphite (HOPG) sample under ambient conditions. Related alkyl-functionalised free base porphyrin molecules are known to form well-ordered monolayers on the same substrate 30,31 . STM revealed the 5 instantaneous self-assembly of the molecules of Mn1Cl in extended lamellar arrays, in which the porphyrin planes are adsorbed parallel to the surface and the alkyl chains interdigitated (Fig. 2B). The orientation of the lamellae and the alkyl chains with respect to the main crystallographic directions of the graphite surface is identical to that observed for the corresponding free base derivative. 30 When the surface was scanned under ambient conditions at a negative bias voltage of −800 mV and ...

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“…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.…”

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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

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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.

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Isolation, purification, and characterization of intermediate (iodosylbenzene)metalloporphyrin complexes from the (tetraphenylporphinato)manganese(III)-iodosylbenzene catalytic hydrocarbon functionalization system

Cited by 125 publications

References 0 publications

Kinetics of (Porphyrin)manganese(III)‐Catalyzed Olefin Epoxidation with a Soluble Iodosylbenzene Derivative

Kinetics of (Porphyrin)manganese(III)‐Catalyzed Olefin Epoxidation with a Soluble Iodosylbenzene Derivative

Detection of different oxidation states of individual manganese porphyrins during their reaction with oxygen at a solid/liquid interface

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

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