Laser Flash Photolysis Generation and Kinetic Studies of Porphyrin−Manganese−Oxo Intermediates. Rate Constants for Oxidations Effected by Porphyrin−Mn<sup>V</sup>−Oxo Species and Apparent Disproportionation Equilibrium Constants for Porphyrin−Mn<sup>IV</sup>−Oxo Species

Zhang, Rui; Horner, John H.; Newcomb, Martin

doi:10.1021/ja045042s

Cited by 169 publications

(223 citation statements)

References 32 publications

Supporting

Mentioning

209

Contrasting

Order By: Relevance

“…Reflections collected 2358 According to earlier works 12 and more recent studies, 13,27,28 axial ligands in aqueous systems. 11,12 In the latter case the Mn(II) species formed in the primary photochemical step (Eq.…”

Section: -7mentioning

confidence: 99%

Functionalization of the benzobicyclo[3.2.1]octadiene skeleton via photocatalytic oxygenation of thiophene and furan derivatives: The impact of the type and position of the heteroatom

Vuk

Kikaš

Molčanov

et al. 2014

Journal of Molecular Structure

View full text Add to dashboard Cite

Photocatalytic oxygenations of a furan and two thiophene derivatives of benzobicyclo[3.2.1]octadiene have been realized by using anionic and cationic manganese(III) porphyrins as catalysts. The replace of oxygen with sulfur in the heteroaromatic ring considerably decreased the reactivity of these heterocyclic compounds, probably due to the increased aromaticity. The end-products of the oxygenation of the thiophene derivatives significantly deviated from most of those formed from the corresponding furan compounds; the lower reactivity of the thiophene ring enhanced the role of the out-of-ring carbon atom in the reaction pathways. Besides, deviating from the behavior of the furan compounds, the types of the end-products formed from the corresponding thiophene derivatives did not depend on the charge of the photocatalyst, neither on the oxygen concentration. However, also in this case, the position of the heteroatom in the aromatic ring strongly affects the formation of the end-products.

show abstract

Section: -7mentioning

confidence: 99%

Functionalization of the benzobicyclo[3.2.1]octadiene skeleton via photocatalytic oxygenation of thiophene and furan derivatives: The impact of the type and position of the heteroatom

Vuk

Kikaš

Molčanov

et al. 2014

Journal of Molecular Structure

View full text Add to dashboard Cite

show abstract

“…

[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.

…”

mentioning

confidence: 99%

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

et al. 2013

View full text Add to dashboard Cite

[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 ...

show abstract

“…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%

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

Laser Flash Photolysis Generation and Kinetic Studies of Porphyrin−Manganese−Oxo Intermediates. Rate Constants for Oxidations Effected by Porphyrin−Mn^V−Oxo Species and Apparent Disproportionation Equilibrium Constants for Porphyrin−Mn^IV−Oxo Species

Cited by 169 publications

References 32 publications

Functionalization of the benzobicyclo[3.2.1]octadiene skeleton via photocatalytic oxygenation of thiophene and furan derivatives: The impact of the type and position of the heteroatom

Functionalization of the benzobicyclo[3.2.1]octadiene skeleton via photocatalytic oxygenation of thiophene and furan derivatives: The impact of the type and position of the heteroatom

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

Contact Info

Product

Resources

About

Laser Flash Photolysis Generation and Kinetic Studies of Porphyrin−Manganese−Oxo Intermediates. Rate Constants for Oxidations Effected by Porphyrin−MnV−Oxo Species and Apparent Disproportionation Equilibrium Constants for Porphyrin−MnIV−Oxo Species

Cited by 169 publications

References 32 publications

Functionalization of the benzobicyclo[3.2.1]octadiene skeleton via photocatalytic oxygenation of thiophene and furan derivatives: The impact of the type and position of the heteroatom

Functionalization of the benzobicyclo[3.2.1]octadiene skeleton via photocatalytic oxygenation of thiophene and furan derivatives: The impact of the type and position of the heteroatom

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

Contact Info

Product

Resources

About

Laser Flash Photolysis Generation and Kinetic Studies of Porphyrin−Manganese−Oxo Intermediates. Rate Constants for Oxidations Effected by Porphyrin−Mn^V−Oxo Species and Apparent Disproportionation Equilibrium Constants for Porphyrin−Mn^IV−Oxo Species