Effect of meso substituents on exchange-coupling interactions in μ-oxo iron(III) porphyrin dimers

Jeffrey H. Helms, Leonard W. Ter Haar, William E. Hatfield, David L. Harris, K. Jayaraj, Glen E. Toney, Avram Gold, Tabitha D. Mewborn, Jeanne E Pemberton

Research output: Contribution to journalArticle

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Abstract

The μ-oxo iron(III) porphyrin dimers [(TPP)Fe]2O, [(TPP(4-OCH3))Fe]2O, [(TPP(4-CF3))Fe]2O, and [(TPP(F5))Fe]2O (where TPP is meso-tetraphenylporphyrin, TPP(4-OCH3) is meso-tetrakis(4-methoxyphenyl)porphyrin, TPP(4-CF3) is meso-tetrakis(4-(trifluoromethyl)phenyl)porphyrin, and TPP(F5) is meso-tetrakis(pentafluorophenyl)porphyrin) have been studied to determine the effect of peripheral substituents on the porphyrin rings on properties of the molecules. Variable-temperature magnetic susceptibility studies on solid samples yielded the following exchange-coupling constants for the antiferromagnetically coupled iron(III) ions: -146.8 cm-1, [(TPP(4-OCH3))Fe]2O; -135.7 cm-1, [(TPP)Fe]2O; -136.4 cm-1, [(TPP(4-CF3))Fe]2O; -146.9 cm-1, [(TPP(F5))Fe]2O. Variable-temperature 13C NMR studies of dichloromethane solutions yield exchange-coupling constants of -150 cm-1 for [(TPP(4-OCH3))Fe]2O, -145 cm-1 for [(TPP)Fe]2O, and -129 cm-1 for [(TPP(F5))Fe]2O. Raman spectra were collected in the region of the energy of the outer-ring stretching modes found at approximately 1560 cm-1. The position of this band is empirically related to the porphyrin core size, and the data indicate that the porphyrin center-pyrrole nitrogen (Ct-N) distances increase in the order [(TPP(F5))Fe]2O < [(TPP(4-CF3))Fe]2O < [(TPP)Fe]2O < [(TPP(4-OCH3))Fe]2O. The data support the hypothesis that the porphyrin ring core size increases as the electron-releasing capability of the peripheral substituent increases. For the para-substituted complexes, increasing core size correlates with stronger axial binding, reflected in stronger antiferromagnetic coupling. The anomalous behavior of [(TPP(F5))Fe]2O may result from distortions caused by steic interactions of the o-fluorines.

Original languageEnglish (US)
Pages (from-to)2334-2337
Number of pages4
JournalInorganic Chemistry
Volume25
Issue number14
StatePublished - 1986

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Exchange coupling
Porphyrins
porphyrins
Dimers
Iron
dimers
iron
interactions
rings
Pyrroles
Fluorine
Methylene Chloride
Magnetic susceptibility
releasing
pyrroles
Stretching
Raman scattering
Nitrogen
fluorine
Nuclear magnetic resonance

ASJC Scopus subject areas

  • Inorganic Chemistry

Cite this

Helms, J. H., Ter Haar, L. W., Hatfield, W. E., Harris, D. L., Jayaraj, K., Toney, G. E., ... Pemberton, J. E. (1986). Effect of meso substituents on exchange-coupling interactions in μ-oxo iron(III) porphyrin dimers. Inorganic Chemistry, 25(14), 2334-2337.

Effect of meso substituents on exchange-coupling interactions in μ-oxo iron(III) porphyrin dimers. / Helms, Jeffrey H.; Ter Haar, Leonard W.; Hatfield, William E.; Harris, David L.; Jayaraj, K.; Toney, Glen E.; Gold, Avram; Mewborn, Tabitha D.; Pemberton, Jeanne E.

In: Inorganic Chemistry, Vol. 25, No. 14, 1986, p. 2334-2337.

Research output: Contribution to journalArticle

Helms, JH, Ter Haar, LW, Hatfield, WE, Harris, DL, Jayaraj, K, Toney, GE, Gold, A, Mewborn, TD & Pemberton, JE 1986, 'Effect of meso substituents on exchange-coupling interactions in μ-oxo iron(III) porphyrin dimers', Inorganic Chemistry, vol. 25, no. 14, pp. 2334-2337.
Helms JH, Ter Haar LW, Hatfield WE, Harris DL, Jayaraj K, Toney GE et al. Effect of meso substituents on exchange-coupling interactions in μ-oxo iron(III) porphyrin dimers. Inorganic Chemistry. 1986;25(14):2334-2337.
Helms, Jeffrey H. ; Ter Haar, Leonard W. ; Hatfield, William E. ; Harris, David L. ; Jayaraj, K. ; Toney, Glen E. ; Gold, Avram ; Mewborn, Tabitha D. ; Pemberton, Jeanne E. / Effect of meso substituents on exchange-coupling interactions in μ-oxo iron(III) porphyrin dimers. In: Inorganic Chemistry. 1986 ; Vol. 25, No. 14. pp. 2334-2337.
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abstract = "The μ-oxo iron(III) porphyrin dimers [(TPP)Fe]2O, [(TPP(4-OCH3))Fe]2O, [(TPP(4-CF3))Fe]2O, and [(TPP(F5))Fe]2O (where TPP is meso-tetraphenylporphyrin, TPP(4-OCH3) is meso-tetrakis(4-methoxyphenyl)porphyrin, TPP(4-CF3) is meso-tetrakis(4-(trifluoromethyl)phenyl)porphyrin, and TPP(F5) is meso-tetrakis(pentafluorophenyl)porphyrin) have been studied to determine the effect of peripheral substituents on the porphyrin rings on properties of the molecules. Variable-temperature magnetic susceptibility studies on solid samples yielded the following exchange-coupling constants for the antiferromagnetically coupled iron(III) ions: -146.8 cm-1, [(TPP(4-OCH3))Fe]2O; -135.7 cm-1, [(TPP)Fe]2O; -136.4 cm-1, [(TPP(4-CF3))Fe]2O; -146.9 cm-1, [(TPP(F5))Fe]2O. Variable-temperature 13C NMR studies of dichloromethane solutions yield exchange-coupling constants of -150 cm-1 for [(TPP(4-OCH3))Fe]2O, -145 cm-1 for [(TPP)Fe]2O, and -129 cm-1 for [(TPP(F5))Fe]2O. Raman spectra were collected in the region of the energy of the outer-ring stretching modes found at approximately 1560 cm-1. The position of this band is empirically related to the porphyrin core size, and the data indicate that the porphyrin center-pyrrole nitrogen (Ct-N) distances increase in the order [(TPP(F5))Fe]2O < [(TPP(4-CF3))Fe]2O < [(TPP)Fe]2O < [(TPP(4-OCH3))Fe]2O. The data support the hypothesis that the porphyrin ring core size increases as the electron-releasing capability of the peripheral substituent increases. For the para-substituted complexes, increasing core size correlates with stronger axial binding, reflected in stronger antiferromagnetic coupling. The anomalous behavior of [(TPP(F5))Fe]2O may result from distortions caused by steic interactions of the o-fluorines.",
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T1 - Effect of meso substituents on exchange-coupling interactions in μ-oxo iron(III) porphyrin dimers

AU - Helms, Jeffrey H.

AU - Ter Haar, Leonard W.

AU - Hatfield, William E.

AU - Harris, David L.

AU - Jayaraj, K.

AU - Toney, Glen E.

AU - Gold, Avram

AU - Mewborn, Tabitha D.

AU - Pemberton, Jeanne E

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N2 - The μ-oxo iron(III) porphyrin dimers [(TPP)Fe]2O, [(TPP(4-OCH3))Fe]2O, [(TPP(4-CF3))Fe]2O, and [(TPP(F5))Fe]2O (where TPP is meso-tetraphenylporphyrin, TPP(4-OCH3) is meso-tetrakis(4-methoxyphenyl)porphyrin, TPP(4-CF3) is meso-tetrakis(4-(trifluoromethyl)phenyl)porphyrin, and TPP(F5) is meso-tetrakis(pentafluorophenyl)porphyrin) have been studied to determine the effect of peripheral substituents on the porphyrin rings on properties of the molecules. Variable-temperature magnetic susceptibility studies on solid samples yielded the following exchange-coupling constants for the antiferromagnetically coupled iron(III) ions: -146.8 cm-1, [(TPP(4-OCH3))Fe]2O; -135.7 cm-1, [(TPP)Fe]2O; -136.4 cm-1, [(TPP(4-CF3))Fe]2O; -146.9 cm-1, [(TPP(F5))Fe]2O. Variable-temperature 13C NMR studies of dichloromethane solutions yield exchange-coupling constants of -150 cm-1 for [(TPP(4-OCH3))Fe]2O, -145 cm-1 for [(TPP)Fe]2O, and -129 cm-1 for [(TPP(F5))Fe]2O. Raman spectra were collected in the region of the energy of the outer-ring stretching modes found at approximately 1560 cm-1. The position of this band is empirically related to the porphyrin core size, and the data indicate that the porphyrin center-pyrrole nitrogen (Ct-N) distances increase in the order [(TPP(F5))Fe]2O < [(TPP(4-CF3))Fe]2O < [(TPP)Fe]2O < [(TPP(4-OCH3))Fe]2O. The data support the hypothesis that the porphyrin ring core size increases as the electron-releasing capability of the peripheral substituent increases. For the para-substituted complexes, increasing core size correlates with stronger axial binding, reflected in stronger antiferromagnetic coupling. The anomalous behavior of [(TPP(F5))Fe]2O may result from distortions caused by steic interactions of the o-fluorines.

AB - The μ-oxo iron(III) porphyrin dimers [(TPP)Fe]2O, [(TPP(4-OCH3))Fe]2O, [(TPP(4-CF3))Fe]2O, and [(TPP(F5))Fe]2O (where TPP is meso-tetraphenylporphyrin, TPP(4-OCH3) is meso-tetrakis(4-methoxyphenyl)porphyrin, TPP(4-CF3) is meso-tetrakis(4-(trifluoromethyl)phenyl)porphyrin, and TPP(F5) is meso-tetrakis(pentafluorophenyl)porphyrin) have been studied to determine the effect of peripheral substituents on the porphyrin rings on properties of the molecules. Variable-temperature magnetic susceptibility studies on solid samples yielded the following exchange-coupling constants for the antiferromagnetically coupled iron(III) ions: -146.8 cm-1, [(TPP(4-OCH3))Fe]2O; -135.7 cm-1, [(TPP)Fe]2O; -136.4 cm-1, [(TPP(4-CF3))Fe]2O; -146.9 cm-1, [(TPP(F5))Fe]2O. Variable-temperature 13C NMR studies of dichloromethane solutions yield exchange-coupling constants of -150 cm-1 for [(TPP(4-OCH3))Fe]2O, -145 cm-1 for [(TPP)Fe]2O, and -129 cm-1 for [(TPP(F5))Fe]2O. Raman spectra were collected in the region of the energy of the outer-ring stretching modes found at approximately 1560 cm-1. The position of this band is empirically related to the porphyrin core size, and the data indicate that the porphyrin center-pyrrole nitrogen (Ct-N) distances increase in the order [(TPP(F5))Fe]2O < [(TPP(4-CF3))Fe]2O < [(TPP)Fe]2O < [(TPP(4-OCH3))Fe]2O. The data support the hypothesis that the porphyrin ring core size increases as the electron-releasing capability of the peripheral substituent increases. For the para-substituted complexes, increasing core size correlates with stronger axial binding, reflected in stronger antiferromagnetic coupling. The anomalous behavior of [(TPP(F5))Fe]2O may result from distortions caused by steic interactions of the o-fluorines.

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