A stable octaethyloxophlorin radical

Fuhrhop, J.‐H.; Besecke, S.; Subramanian, J.

doi:10.1039/c39730000001

Cited by 17 publications

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“…Reactions at the periphery of 5-oxophlorins occur preferentially at the electron-rich position-15 [271]. Neutral π-radicals of 5-oxophlorins are easily formed under mild conditions, and were shown to be stabilized by bulky 15-substituents [272, 273].…”

Section: Porphyrin Functionalizationmentioning

confidence: 99%

Syntheses and Functionalizations of Porphyrin Macrocycles

Vicente¹,

Smith²

2014

COS

108

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Porphyrin macrocycles have been the subject of intense study in the last century because they are widely distributed in nature, usually as metal complexes of either iron or magnesium. As such, they serve as the prosthetic groups in a wide variety of primary metabolites, such as hemoglobins, myoglobins, cytochromes, catalases, peroxidases, chlorophylls, and bacteriochlorophylls; these compounds have multiple applications in materials science, biology and medicine. This article describes current methodology for preparation of simple, symmetrical model porphyrins, as well as more complex protocols for preparation of unsymmetrically substituted porphyrin macrocycles similar to those found in nature. The basic chemical reactivity of porphyrins and metalloporphyrin is also described, including electrophilic and nucleophilic reactions, oxidations, reductions, and metal-mediated cross-coupling reactions. Using the synthetic approaches and reactivity profiles presented, eventually almost any substituted porphyrin system can be prepared for applications in a variety of areas, including in catalysis, electron transport, model biological systems and therapeutics.

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Section: Porphyrin Functionalizationmentioning

confidence: 99%

Syntheses and Functionalizations of Porphyrin Macrocycles

Vicente¹,

Smith²

2014

COS

108

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“…Heme oxygenase converts unwanted heme to biliverdin in animals and birds. − Two major intermediates isolated and characterized in this heme oxygenase process or in coupled oxidation model system are oxophlorin and verdoheme − (see Scheme ).…”

Section: Introductionmentioning

confidence: 99%

Effect of Axial Ligand on the Electronic Configuration, Spin States, and Reactivity of Iron Oxophlorin

2012

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Iron-oxophlorin is an intermediate in heme degradation, and the nature of the axial ligand can alter the spin, electron distribution, and reactivity of the metal and the oxophlorin ring. The structure and reactivity of iron-oxophlorin in the presence of imidazole, pyridine, and t-butyl isocyanide as axial ligands was investigated using the B3LYP and OPBE methods with the 6-31+G* and 6-311+G** basis sets. OPBE/6-311+G** has shown that the doublet state of [(Py)(2)Fe(III)(PO)] (where pyridines are in perpendicular planes and PO is the oxophlorin trianion) is 3.45 and 5.27 kcal/mol more stable than the quartet and sextet states, respectively. The ground-state electronic configuration of the aforementioned complex is π(xz)(2) π(yz)(2) a(2u)(2) d(xy)(1) at low temperatures and changes to π(xz)(2) π(yz)(2) d(xy)(2) a(2u)(1) at high temperatures. This latter electronic configuration is consistently seen for the [(t-BuNC)(2)Fe(II)(PO(•))] complex (where PO(•) is the oxophlorin dianion radical). The complex [(Im)(2)Fe(III)(PO)] adopted the d(xy)(2) (π(xz) π(yz))(3) ground state and has low-lying quartet excited state which is readily populated when the temperature is increased.

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“…Heme catabolism is an important physiological process that is carried out by O 2 /NADPH in the presence of heme oxygenase enzyme/HO in animals and birds. Heme oxygenase performs the essential role of destroying unwanted heme. − The coupled oxidation in which heme degradation occurs via O 2 /reducing agent in a coordinating solvent has been widely used as a model for biological heme catabolism. − Three major intermediates isolated and characterized in this heme oxygenase process or in a coupled oxidation model system are α-hydroxyheme, oxophlorin, and verdoheme, ,− Scheme .…”

Section: Introductionmentioning

confidence: 99%

Structure and Redox Behavior of Iron Oxophlorin and Role of Electron Transfer in the Heme Degradation Process

2012

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Iron-oxophlorin is an intermediate in heme degradation, and the metal oxidation number can alter spin, electron distribution, and the reactivity of the metal and the oxophlorin ring. The role of electron transfer in the structure and reactivity of [(Py)(2)Fe(III)(PO)] (PO is the oxophlorin trianion) in different redox states has been investigated using the B3LYP and OPBE methods with the 6-31+G* and 6-311+G** basis sets. A computation study has shown that [(py)(2) Fe(III)(PO)] loses one electron from its a(2u) orbital. Thus the oxidized species, [(Py)(2)Fe(III)(PO(•))](+) (where PO(•) is the oxophlorin dianion radical), has an open-shell-singlet ground state with a d(xy)(2) d(xz)(2) a(2u)(1) d(yz)(1) electronic configuration with closely lying triplet and quintet states which are populated at ambient temperature. The aforementioned complex is highly reactive toward O(2). The reduced species [(Py)(2)Fe(II)(POH)] (where POH is the hydroxyheme) has the closed-shell-singlet ground state (π(xz) π(yz))(4) a(2u)(2) d(xy)(2) electronic configuration in which pyridines have a more π-accepting character and, thus, are tightly bound to iron. This reduced form is considerably less reactive toward O(2). The axial ligands effects (Im, t-BuNC) have also been studied in redox reactions of iron oxophlorin complexes. Complex [(Im)(2)Fe(III)(PO)] shows facile oxidation to form a cation radical and a reduction to form hydroxy while the [(t-BuNC)(2)Fe(II)(PO(•))] has high positive oxidation potential.

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A stable octaethyloxophlorin radical

Abstract: Sutnwzary Octaethyloxophlorin (I) yields the stable radical direct oxidation of the zinc octaethyloxophlorin with (11) on aerial oxidation ; traces of such autoxidation oxygen or bromoacetamide. products are considered to account for the paramagnetism reported for oxophlorins.

Cited by 17 publications

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Syntheses and Functionalizations of Porphyrin Macrocycles

Syntheses and Functionalizations of Porphyrin Macrocycles

Effect of Axial Ligand on the Electronic Configuration, Spin States, and Reactivity of Iron Oxophlorin

Structure and Redox Behavior of Iron Oxophlorin and Role of Electron Transfer in the Heme Degradation Process

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