Characterization of a true intermediate-spin (porphinato)iron(III) complex

Toney, G. E.; Terhaar, L. W.; Savrin, J. E.; Gold, A.; Hatfield, William E.; Sangaiah, R.

doi:10.1021/ic00185a004

Cited by 32 publications

(32 citation statements)

References 2 publications

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“…We note, however, the many examples of similar phenomena in iron(III) porphyrins. In contrast to the case of halo-coordinated Fe(III) porphyrins, which are purely high spin ( S = 5 / 2 ), in all perchlorato derivatives the metal is intermediate spin to some degree, ranging from S = 5 / 2 , S = 3 / 2 spin admixtures to purely S = 3 / 2 …”

Section: Resultsmentioning

confidence: 81%

Spin Transition in a Manganese(III) Porphyrin Cation Radical, Its Transformation to a Dichloromanganese(IV) Porphyrin, and Chlorination of Hydrocarbons by the Latter

et al. 1997

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Chemical oxidation of (TMP)Mn(III)(Cl) (TMP = the tetramesitylporphyrinato dianion) by Fe(ClO(4))(3) leads to the porphyrin-oxidized product (TMP(*)(+))Mn(III)(ClO(4))(2). Magnetic measurements and EPR spectroscopy show that the total spin of the complex changes from S = (5)/(2) at high temperature to S = (3)/(2) at low temperature. Ligand exchange of the perchlorato ligands in (TMP(*)(+))Mn(III)(ClO(4))(2) by chloride anions is accompanied by a change of the oxidation site from porphyrin to metal, resulting in (TMP)Mn(IV)(Cl)(2). This high-valent-metal complex can effect chlorine atom transfer to olefins, as well as to dimedone and chlorodimedone, natural substrates of chloroperoxidases.

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Section: Resultsmentioning

confidence: 81%

Spin Transition in a Manganese(III) Porphyrin Cation Radical, Its Transformation to a Dichloromanganese(IV) Porphyrin, and Chlorination of Hydrocarbons by the Latter

et al. 1997

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“…The axial ligands and the nature of the porphyrin are the primary determinants of the spin state. Pure 4-coordinate Fe(III) porphyrins without axial coordination are intermediate spin ( S = 3 / 2 ) 17 . Axial coordination of two oxygen ligands gives rise to an admixed-spin state ( S = 3 / 2 , 5 / 2 ) if they are weak, or a high-spin species ( S = 5 / 2 ) if they are strong.…”

Section: Resultsmentioning

confidence: 99%

Light-controlled switching of the spin state of iron(III)

et al. 2018

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Controlled switching of the spin state of transition metal ions, particularly of FeII and FeIII, is a prerequisite to achieve selectivity, efficiency, and catalysis in a number of metalloenzymes. Here we report on an iron(III) porphyrin with a photochromic axial ligand which, upon irradiation with two different wavelengths reversibly switches its spin state between low-spin (S = 1/2) and high-spin (S = 5/2) in solution (DMSO-acetone, 2:598). The switching efficiency is 76% at room temperature. The system is neither oxygen nor water sensitive, and no fatigue was observed after more than 1000 switching cycles. Concomitant with the spin-flip is a change in redox potential by ~60 mV. Besides serving as a simple model for the first step of the cytochrome P450 catalytic cycle, the spin switch can be used to switch the spin-lattice relaxation time T1 of the water protons by a factor of 15.

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“…It is known that many Fe III (P)ClO 4 complexes adopt the spin-admixed or intermediate spin electronic configuration ( S = 3 / 2 ). For intermediate-spin complexes, the 1 H NMR spectra show the pyr-H resonance near −30 ppm and an ESR signal at g = 4.2. 22a,b We have, however, examined the ESR spectrum of Fe III (TMP)ClO 4 in CH 2 Cl 2 at 110 K, which reveals that it is predominantly high spin, since it exhibits a typical signal at g = 6. 22b,c It has been suggested 22d that the isotropic shifts of the pyr-H resonances in the 1 H NMR spectra of Fe III (P)L complexes are due to M → L σ-spin transfer. The observed signals for the pyr-H of this series of complexes show a monotonic shift, implying the following order of ligand σ-donor strength: F - > Cl - > AcO - > trif - > ClO 4 - (i.e., δ pyr = 81.5, 80.3, 79.6, 52.6, and 29.2 ppm, respectively).…”

Section: Resultsmentioning

confidence: 99%

Direct Resonance Raman Evidence for a Trans Influence on the Ferryl Fragment in Models of Compound I Intermediates of Heme Enzymes

et al. 1996

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Resonance Raman (RR) spectra are reported for a series of ferric complexes of meso-tetramesitylporphyrin XFeIII(TMP) (where X = F-, Cl-, m-chlorobenzoate (mCB-), CF3O2SO- (trif-) and ClO4 -) and their oxidized derivatives, OFeIV(TMP•+)(X). Mode assignments are made by RR studies of the β-pyrrole-deuterated and 18O-labeled analogues. The results demonstrate that the oxo−iron bond strength is sensitive to the nature of the trans-axial ligand (X), the ν(FeO) stretching mode appearing near 800 cm-1 for the F-, Cl-, and mCB- complexes and near 835 cm-1 for the trif- and ClO4 - complexes. The high-frequency marker modes and the 1H chemical shifts are consistent with stronger electron donation by the former three anions. An explanation for the apparent absence of a correlation between the ν(FeO) stretching frequencies and the previously reported rate constants for substrate epoxidation is also suggested.

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Characterization of a true intermediate-spin (porphinato)iron(III) complex

Cited by 32 publications

References 2 publications

Spin Transition in a Manganese(III) Porphyrin Cation Radical, Its Transformation to a Dichloromanganese(IV) Porphyrin, and Chlorination of Hydrocarbons by the Latter

Spin Transition in a Manganese(III) Porphyrin Cation Radical, Its Transformation to a Dichloromanganese(IV) Porphyrin, and Chlorination of Hydrocarbons by the Latter

Light-controlled switching of the spin state of iron(III)

Direct Resonance Raman Evidence for a Trans Influence on the Ferryl Fragment in Models of Compound I Intermediates of Heme Enzymes

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