Heme/Hydrogen Peroxide Reactivity:  Formation of Paramagnetic Iron Oxophlorin Isomers by Treatment of Iron Porphyrins with Hydrogen Peroxide

Kalish, Heather; Latos-Grażyński, and Lechosław; Balch, Alan L.

doi:10.1021/ja0016405

Cited by 31 publications

(34 citation statements)

References 36 publications

(51 reference statements)

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“…The pyrrole pattern determined for [(5-O-TrPP)Fe(py) 2 ] was found to be very similar to that determined from the rather complex analysis carried out for four (oxophlorin)iron regioisomers obtained from hemes. [26] The relatively large paramagnetic shift of the meso-phenyl resonances dominated by the π-contact mechanism reflects the large spin density at the meso positions, as found previously for other (oxophlorin)-iron complexes. In conclusion, the spin-density distribution in the oxophlorin skeleton is dominated by the location of the oxygenated meso site and that this functional group imposes a basic twofold electronic symmetry that is only moderately perturbed by the presence of other functional groups.…”

Section: Electronic Structure Of [(5-o-trpp)fe(py) 2 ] and [(5-otrpp)supporting

confidence: 66%

“…We have taken into account that porphyrins themselves are not nearly as susceptible to initial meso oxygenation (hydroxylation) as are (porphyrin)iron complexes. [26,46,47] Consequently, the reaction of [(TrPP)Fe II (py) 2 ] with hydrogen peroxide at Ϫ30°C in the absence of dioxygen has been examined. Scheme 2 shows the structures and transformations involved.…”

Section: Reaction Of Hydrogen Peroxide With [(Trpp)fe II (Py) 2 ]mentioning

confidence: 99%

“…[31,56] ester, and protoporphyrin-IX dimethyl ester, respectively). [22,26,46] Based on the chemical shifts measured for the four (deuterooxophlorin)iron isomers [(DeuteroPO)Fe(py) 2 ], the following values are anticipated for (5-oxophlorin)iron or its β-methylated derivative: pyrrole resonances: δ ϭ Ϫ33 (2-H), 27 (3-H), 13 (12-and 13-H) ppm; methyl resonances: δ ϭ 65 (2-CH 3 ), Ϫ14 (3-CH 3 ) ppm. Substitution of a methyl group by a proton is expected to give rise to a resonance that is subject to a hyperfine shift of opposite sign, but a magnitude similar to that of the corresponding methyl group if π-spin delocalization dominates the hyperfine shifts.…”

Section: Electronic Structure Of [(5-o-trpp)fe(py) 2 ] and [(5-otrpp)mentioning

confidence: 99%

“…Consequently, the pyrrole β-H resonances with the largest hyperfine shifts and the methyl resonances with the most upfield shift must originate from a common site (i.e., from a site with similar value and sign of the spin density) within the molecule as has been well documented for four regioisomers of [(DeuteroPO)Fe(py) 2 ]. [26] The four pyrrole protons of [(5-O-TrPP)Fe(py) 2 ] provide direct probes of the spin density around the oxophlorin macrocycle. In principle, this should allow the determination of the differences in the contact shifts for four pyrrole rings avoiding any differences due to the unsymmetrical substitution effect expected for natural porphyrins.…”

Section: Electronic Structure Of [(5-o-trpp)fe(py) 2 ] and [(5-otrpp)mentioning

confidence: 99%

“…[12,27] It is widely accepted that the first step in heme degradation by heme oxygenase results in the meso hydroxylation of heme. [12,23,26,28,29] Direct spectroscopic evidence has been presented showing that meso-hydroxylated heme is formed by heme oxygenase. [30] 1 H NMR spectroscopy provides a uniquely useful probe for studying the structure of (porphyrin)iron complexes in solution.…”

Section: Introductionmentioning

confidence: 99%

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Monomeric and Dimeric Iron(III) Complexes of 5‐Hydroxy‐10,15,20‐triphenylporphyrin: Formation of Cyano and Pyridine Complexes of (5‐Oxo‐10,15,20‐triphenylphlorin)iron

Wojaczyński

Stępień

Latos‐Grażyński

2002

Euro J of Inorganic Chem

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The reaction of [(TrPP)FeII(py)2] (TrPP = dianion of 5,10,15‐triphenylporphyrin) with hydrogen peroxide results in oxygenation of the (porphyrin)iron and the formation of (10,15,20‐triphenyl‐5‐oxophlorin)iron [(5‐O‐TrPP)Fe(py)2]. Coupled oxidation of [(TrPP)FeIIICl] in the presence of ascorbic acid and potassium cyanide in methanol leads to oxidative hydroxylation of the porphyrin ring to form a cyclic dimer [(5‐O‐TrPP)FeIII]2. Three out of four pyrrole 1H NMR resonances of the dimeric complex present the characteristic displacement with respect to the typical position for the high‐spin (tetraphenylporphyrin)iron(III) complexes. The linewidths of the β‐H pyrrole resonances correlate with specific locations of the respective protons within the dimeric structure. Addition of HCl to [(5‐O‐TrPP)FeIII]2 results in cleavage of the dimer producing [(5‐OH‐TrPP)FeIIICl]. [(5‐O‐TrPP)FeIII]2 is also split with acetic anhydride to give (5‐acetoxy‐10,15,20‐triphenylporphyrin)iron(III). In the presence of [D5]pyridine or a large excess of cyanide ion, [(5‐O‐TrPP)FeIII]2 undergoes cleavage to form air‐sensitive [(5‐O‐TrPP)Fe(py)2] or [(5‐O‐TrPP)Fe(CN)2]2−. The pyrrole pattern observed for [(5‐O‐TrPP)Fe(py)2] is similar to that determined on the basis of an analysis carried out for four (oxophlorin)iron regioisomers obtained from hemes. For comparison, the characteristic 1H NMR features of the typical (5‐substituted‐10,15,20‐triphenylporphyrin)iron(III) complexes have been investigated for the series of high‐spin and low‐spin complexes. The spin‐density distribution in the (oxophlorin)iron skeleton is dominated by the radical‐like electronic structure. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

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Section: Electronic Structure Of [(5-o-trpp)fe(py) 2 ] and [(5-otrpp)supporting

confidence: 66%

Section: Reaction Of Hydrogen Peroxide With [(Trpp)fe II (Py) 2 ]mentioning

confidence: 99%

Section: Electronic Structure Of [(5-o-trpp)fe(py) 2 ] and [(5-otrpp)mentioning

confidence: 99%

Section: Electronic Structure Of [(5-o-trpp)fe(py) 2 ] and [(5-otrpp)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Monomeric and Dimeric Iron(III) Complexes of 5‐Hydroxy‐10,15,20‐triphenylporphyrin: Formation of Cyano and Pyridine Complexes of (5‐Oxo‐10,15,20‐triphenylphlorin)iron

Wojaczyński

Stępień

Latos‐Grażyński

2002

Euro J of Inorganic Chem

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Iron Porphyrin Chemistry

Walker¹,

Simonis²

2005

Encyclopedia of Inorganic Chemistry

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This article reviews most aspects of the chemistry of iron porphyrins, from Fe(0) to Fe(V), including occurrence and roles of natural iron porphyrins (hemes) and their synthetic analogs, structures and electron configurations of iron porphyrins of all oxidation and spin states, π electron configuration of the porphyrin ring, synthesis of metal‐free porphyrins and other related macrocycles, insertion of iron into free‐base porphyrins and related macrocycles, the properties, reactions, uses and biological relevance of iron(0), ‐(I), ‐(II) porphyrins (the latter with S = 0, 1, and 2 spin state possibilities), of iron(II) porphyrin π‐cation radicals, of iron(III) porphyrins (with S = 1/2, 3/2, and 5/2 spin state possibilities), of iron(III) porphyrin and corrole π‐cation radicals, of iron(IV) porphyrins (including five‐ and six‐coordinate ferryl (FeO) 2+ , iron(IV) phenyl, carbene and hydrazine complexes, and the bis‐methoxide complex) and a comparison of iron(IV) porphyrins to iron(III) porphyrin π‐cation radicals, of iron(IV) porphyrin π‐cation radicals, and of the possible existence of iron(V) porphyrins. Included in the Fe(II) part are sections on addition of ligands to four‐coordinate iron(II) porphyrins, including equilibrium binding constants, photodissociation of ligands from PFeL 2 complexes, binding of small molecules (O 2 , CO, NO, HNO) to 5‐coordinate iron(II) porphyrins and design of porphyrin ligands that will mimic the active sites of heme proteins such as myoglobin and hemoglobin, the cytochromes P450 and nitric oxide synthases, and the nitrophorins and guanylyl cyclases. Included in the iron(III) part are sections on both 5‐ and 6‐coordinate high‐spin complexes and their similarities and differences, bridged or through‐space magnetically coupled complexes of high‐spin iron(III) porphyrins with other metal complexes as possible models for cytochrome oxidase and the assimilatory sulfite reductases, coupled oxidation of hemes by hydrogen peroxide or its equivalent, and the relationship of this reactivity to the reactions of heme oxygenase, iron(III) porphyrins as reduction catalysts, and photochemistry of iron(III) porphyrins, possible electron configurations of low‐spin iron(III) porphyrins, the phenomenon and possible electronic consequences of ruffling of the porphinato core in iron(III) porphyrins, the preferred orientation of planar axial ligands bound to low‐spin iron(III) porphyrins, NO complexes of iron(III) porphyrins, reduction potentials, equilibrium constants and rates of axial‐ligand addition and exchange, kinetics of axial‐ligand rotation and porphyrin ring inversion, kinetics of reduction and autoreduction of iron(III) porphyrins, electron self‐exchange between low‐spin iron(III) and iron(II) porphyrins, synthetic ferriheme proteins, and synthesis of five‐coordinate low‐spin iron(III) porphyrins having σ‐alkyl or σ‐aryl groups as axial ligands. The iron(IV) and iron(IV) cation radical sections discuss the high‐valent states of cytochromes P450 and related enzymes.

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