Syntheses, NMR and EPR spectroscopy, electrochemical properties, and structural studies of [5,10,15,20- tetrakis(perfluoroalkyl)porphinato]iron(II) and -iron(III) complexes

Kevin T. Moore, James T. Fletcher, Michael J. Therien

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Abstract

Syntheses, structural studies, electrochemistry, and spectroscopy of a number of [5,10,15,20-tetrakis(heptafluoropropyl)porphinato]iron derivatives are presented. The X-ray crystal structure of 5,10,15,20- tetrakis(heptafluoropropyl)porphinato]iron(II)·(pyridine)2 exhibits a substantial S4 distortion of the porphyrin macrocycle, with the meso-carbon atoms displaced more than 0.6 Å above and below the porphyrin mean plane defined by the four central nitrogen atoms; the most notable aspect of this ferrous porphyrin structure is the fact that it exhibits metrical features commonly manifested in crystallographically characterized ferric porphyrin complexes. X-ray data are as follows: P21/n with a = 12.772(1) Å, b = 18.895(2) Å, c = 19.756(2) Å, β = 99.960(6)°, V = 4695.7(8) Å3, Z = 4, and d(calc) = 1.689 g/cm3. 19F NMR spectroscopy confirms the sensitivity of the 19F nucleus as a probe of macrocycle aromaticity and electronic structure, while 1H NMR spectroscopic studies show large isotropic shifts for the β-protons of the (porphinato)iron(III) chloride derivative (δ = 101.5 and 86.4 ppm). Electrochemical data obtained from cyclic voltammetric and spectroelectrochemical experiments reveal that the E(1/2) value for the Fe(II/III) redox couple for 5,10,15,20- tetrakis(heptafluoropropyl)porphinato]iron·(pyridine)2 is shifted by 550 mV relative to that observed for the corresponding (porphinato)iron(III) chloride complex. The cathodic electrochemistry of [5,10,15,20- tetrakis(heptafuoropropyl)porphinato]iron·(pyridine)2 is also unusual in that the first one-electron reduction of this complex produces a largely macrocycle-localized radical anion. EPR spectroscopic data shows that 5,10,15,20-tetrakis(heptafluoropropyl)porphinato]iron(III)·(pyridine)2 manifests a pure axial spectrum (Δ/λ = -26.4; Σg2 = 12.53) congruent with a (d(xz),d(yz))4(d(xy))1 electronic ground state. The extraordinary structural, potentiometric, and spectroscopic properties of these (porphinato)iron species arise from substantially reduced metal-centered electron density effected by the macrocycle's non-π-conjugating, σ- electron-withdrawing meso-perfluoroalkyl substituents.

Original languageEnglish
Pages (from-to)5196-5209
Number of pages14
JournalJournal of the American Chemical Society
Volume121
Issue number22
DOIs
StatePublished - Jun 9 1999
Externally publishedYes

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Electrochemical properties
Paramagnetic resonance
Magnetic Resonance Spectroscopy
Iron
Nuclear magnetic resonance
Spectroscopy
Porphyrins
Pyridine
Electrochemistry
Electrons
Chlorides
X-Rays
Derivatives
X rays
Atoms
Ground state
Nuclear magnetic resonance spectroscopy
Oxidation-Reduction
Electronic structure
Anions

All Science Journal Classification (ASJC) codes

  • Chemistry(all)

Cite this

@article{1bd7b1205bb24c8991b64580c4740ae3,
title = "Syntheses, NMR and EPR spectroscopy, electrochemical properties, and structural studies of [5,10,15,20- tetrakis(perfluoroalkyl)porphinato]iron(II) and -iron(III) complexes",
abstract = "Syntheses, structural studies, electrochemistry, and spectroscopy of a number of [5,10,15,20-tetrakis(heptafluoropropyl)porphinato]iron derivatives are presented. The X-ray crystal structure of 5,10,15,20- tetrakis(heptafluoropropyl)porphinato]iron(II)·(pyridine)2 exhibits a substantial S4 distortion of the porphyrin macrocycle, with the meso-carbon atoms displaced more than 0.6 {\AA} above and below the porphyrin mean plane defined by the four central nitrogen atoms; the most notable aspect of this ferrous porphyrin structure is the fact that it exhibits metrical features commonly manifested in crystallographically characterized ferric porphyrin complexes. X-ray data are as follows: P21/n with a = 12.772(1) {\AA}, b = 18.895(2) {\AA}, c = 19.756(2) {\AA}, β = 99.960(6)°, V = 4695.7(8) {\AA}3, Z = 4, and d(calc) = 1.689 g/cm3. 19F NMR spectroscopy confirms the sensitivity of the 19F nucleus as a probe of macrocycle aromaticity and electronic structure, while 1H NMR spectroscopic studies show large isotropic shifts for the β-protons of the (porphinato)iron(III) chloride derivative (δ = 101.5 and 86.4 ppm). Electrochemical data obtained from cyclic voltammetric and spectroelectrochemical experiments reveal that the E(1/2) value for the Fe(II/III) redox couple for 5,10,15,20- tetrakis(heptafluoropropyl)porphinato]iron·(pyridine)2 is shifted by 550 mV relative to that observed for the corresponding (porphinato)iron(III) chloride complex. The cathodic electrochemistry of [5,10,15,20- tetrakis(heptafuoropropyl)porphinato]iron·(pyridine)2 is also unusual in that the first one-electron reduction of this complex produces a largely macrocycle-localized radical anion. EPR spectroscopic data shows that 5,10,15,20-tetrakis(heptafluoropropyl)porphinato]iron(III)·(pyridine)2 manifests a pure axial spectrum (Δ/λ = -26.4; Σg2 = 12.53) congruent with a (d(xz),d(yz))4(d(xy))1 electronic ground state. The extraordinary structural, potentiometric, and spectroscopic properties of these (porphinato)iron species arise from substantially reduced metal-centered electron density effected by the macrocycle's non-π-conjugating, σ- electron-withdrawing meso-perfluoroalkyl substituents.",
author = "Moore, {Kevin T.} and Fletcher, {James T.} and Therien, {Michael J.}",
year = "1999",
month = "6",
day = "9",
doi = "10.1021/ja9816741",
language = "English",
volume = "121",
pages = "5196--5209",
journal = "Journal of the American Chemical Society",
issn = "0002-7863",
publisher = "American Chemical Society",
number = "22",

}

TY - JOUR

T1 - Syntheses, NMR and EPR spectroscopy, electrochemical properties, and structural studies of [5,10,15,20- tetrakis(perfluoroalkyl)porphinato]iron(II) and -iron(III) complexes

AU - Moore, Kevin T.

AU - Fletcher, James T.

AU - Therien, Michael J.

PY - 1999/6/9

Y1 - 1999/6/9

N2 - Syntheses, structural studies, electrochemistry, and spectroscopy of a number of [5,10,15,20-tetrakis(heptafluoropropyl)porphinato]iron derivatives are presented. The X-ray crystal structure of 5,10,15,20- tetrakis(heptafluoropropyl)porphinato]iron(II)·(pyridine)2 exhibits a substantial S4 distortion of the porphyrin macrocycle, with the meso-carbon atoms displaced more than 0.6 Å above and below the porphyrin mean plane defined by the four central nitrogen atoms; the most notable aspect of this ferrous porphyrin structure is the fact that it exhibits metrical features commonly manifested in crystallographically characterized ferric porphyrin complexes. X-ray data are as follows: P21/n with a = 12.772(1) Å, b = 18.895(2) Å, c = 19.756(2) Å, β = 99.960(6)°, V = 4695.7(8) Å3, Z = 4, and d(calc) = 1.689 g/cm3. 19F NMR spectroscopy confirms the sensitivity of the 19F nucleus as a probe of macrocycle aromaticity and electronic structure, while 1H NMR spectroscopic studies show large isotropic shifts for the β-protons of the (porphinato)iron(III) chloride derivative (δ = 101.5 and 86.4 ppm). Electrochemical data obtained from cyclic voltammetric and spectroelectrochemical experiments reveal that the E(1/2) value for the Fe(II/III) redox couple for 5,10,15,20- tetrakis(heptafluoropropyl)porphinato]iron·(pyridine)2 is shifted by 550 mV relative to that observed for the corresponding (porphinato)iron(III) chloride complex. The cathodic electrochemistry of [5,10,15,20- tetrakis(heptafuoropropyl)porphinato]iron·(pyridine)2 is also unusual in that the first one-electron reduction of this complex produces a largely macrocycle-localized radical anion. EPR spectroscopic data shows that 5,10,15,20-tetrakis(heptafluoropropyl)porphinato]iron(III)·(pyridine)2 manifests a pure axial spectrum (Δ/λ = -26.4; Σg2 = 12.53) congruent with a (d(xz),d(yz))4(d(xy))1 electronic ground state. The extraordinary structural, potentiometric, and spectroscopic properties of these (porphinato)iron species arise from substantially reduced metal-centered electron density effected by the macrocycle's non-π-conjugating, σ- electron-withdrawing meso-perfluoroalkyl substituents.

AB - Syntheses, structural studies, electrochemistry, and spectroscopy of a number of [5,10,15,20-tetrakis(heptafluoropropyl)porphinato]iron derivatives are presented. The X-ray crystal structure of 5,10,15,20- tetrakis(heptafluoropropyl)porphinato]iron(II)·(pyridine)2 exhibits a substantial S4 distortion of the porphyrin macrocycle, with the meso-carbon atoms displaced more than 0.6 Å above and below the porphyrin mean plane defined by the four central nitrogen atoms; the most notable aspect of this ferrous porphyrin structure is the fact that it exhibits metrical features commonly manifested in crystallographically characterized ferric porphyrin complexes. X-ray data are as follows: P21/n with a = 12.772(1) Å, b = 18.895(2) Å, c = 19.756(2) Å, β = 99.960(6)°, V = 4695.7(8) Å3, Z = 4, and d(calc) = 1.689 g/cm3. 19F NMR spectroscopy confirms the sensitivity of the 19F nucleus as a probe of macrocycle aromaticity and electronic structure, while 1H NMR spectroscopic studies show large isotropic shifts for the β-protons of the (porphinato)iron(III) chloride derivative (δ = 101.5 and 86.4 ppm). Electrochemical data obtained from cyclic voltammetric and spectroelectrochemical experiments reveal that the E(1/2) value for the Fe(II/III) redox couple for 5,10,15,20- tetrakis(heptafluoropropyl)porphinato]iron·(pyridine)2 is shifted by 550 mV relative to that observed for the corresponding (porphinato)iron(III) chloride complex. The cathodic electrochemistry of [5,10,15,20- tetrakis(heptafuoropropyl)porphinato]iron·(pyridine)2 is also unusual in that the first one-electron reduction of this complex produces a largely macrocycle-localized radical anion. EPR spectroscopic data shows that 5,10,15,20-tetrakis(heptafluoropropyl)porphinato]iron(III)·(pyridine)2 manifests a pure axial spectrum (Δ/λ = -26.4; Σg2 = 12.53) congruent with a (d(xz),d(yz))4(d(xy))1 electronic ground state. The extraordinary structural, potentiometric, and spectroscopic properties of these (porphinato)iron species arise from substantially reduced metal-centered electron density effected by the macrocycle's non-π-conjugating, σ- electron-withdrawing meso-perfluoroalkyl substituents.

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