Electron configuration of ferric ions in low-spin (dicyano)(meso-tetraarylporphyrinato)iron(III) complexes

Mikio Nakamura, Takahisa Ikeue, Akira Ikezaki, Yoshiki Ohgo, Hiroshi Fujii

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Abstract

The electron configuration of a series of low-spin (dicyano){meso-tetrakis(2,4,6-trialkylphenyl)porphyrinato}iron(III) complexes, [Fe(R-TPP)(CN)2]- where R = Me, Et, or iPr, together with the parent [Fe(TPP)(CN)2]-, has been examined in dichloromethane-methanol solution by 1H NMR, 13C NMR, and EPR spectroscopies. While the ferric ion of [Fe(TPP)(CN)2]- has shown a common (dxy)2(dxzdyz)3 configuration, the ferric ions of the alkyl-substituted complexes [Fe(R-TPP)(CN)2]- have exhibited the preference of a less common (dxz,dyz)4(dxy)1 configuration. Spectroscopic characteristics of the complexes in which ferric ions take the (dxz,dyz)4(dxy)1 configuration are (i) axial type EPR spectra, (ii) downfield shifted pyrrole and meta signals in 1H NMR spectra, and (iii) downfield shifted meso-caibon signals in 13C NMR spectra. Occurrence of the less common (dxz,dyz)4(dxy)1 configuration in [Fe(R-TPP)(CN)2]- has been ascribed to the electronic interaction between iron(dπ) and cyanide(pπ*) orbitals. The interaction stabilizes the dπ orbitals and induces (dxzdyz)4(dxy)1 configuration. Since the electron configuration of (dicyano){meso-tetrakis(2,6-dichlorophenyI)porphyrinato}iron(III), [Fe(Cl-TPP)(CN)2]-, which carries bulky electronegative chlorine atoms at the ortho positions, is presented as a common (dxy)2(dxzdyz)3, the less common (dxz,dyz)4(dxy)1 configuration in [Fe(R-TPP)(CN)2]- can be ascribed, at least partially, to the electron-donating ability of the meso-aryl groups.

Original languageEnglish
Pages (from-to)3857-3862
Number of pages6
JournalInorganic Chemistry
Volume38
Issue number17
Publication statusPublished - 1999

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ferric ions
Iron
Nuclear magnetic resonance
Ions
iron
Electrons
configurations
Paramagnetic resonance
electrons
nuclear magnetic resonance
Pyrroles
Methylene Chloride
Chlorine
Cyanides
Methanol
Spectroscopy
orbitals
Atoms
cyanides
pyrroles

ASJC Scopus subject areas

  • Inorganic Chemistry

Cite this

Nakamura, M., Ikeue, T., Ikezaki, A., Ohgo, Y., & Fujii, H. (1999). Electron configuration of ferric ions in low-spin (dicyano)(meso-tetraarylporphyrinato)iron(III) complexes. Inorganic Chemistry, 38(17), 3857-3862.

Electron configuration of ferric ions in low-spin (dicyano)(meso-tetraarylporphyrinato)iron(III) complexes. / Nakamura, Mikio; Ikeue, Takahisa; Ikezaki, Akira; Ohgo, Yoshiki; Fujii, Hiroshi.

In: Inorganic Chemistry, Vol. 38, No. 17, 1999, p. 3857-3862.

Research output: Contribution to journalArticle

Nakamura, M, Ikeue, T, Ikezaki, A, Ohgo, Y & Fujii, H 1999, 'Electron configuration of ferric ions in low-spin (dicyano)(meso-tetraarylporphyrinato)iron(III) complexes', Inorganic Chemistry, vol. 38, no. 17, pp. 3857-3862.
Nakamura, Mikio ; Ikeue, Takahisa ; Ikezaki, Akira ; Ohgo, Yoshiki ; Fujii, Hiroshi. / Electron configuration of ferric ions in low-spin (dicyano)(meso-tetraarylporphyrinato)iron(III) complexes. In: Inorganic Chemistry. 1999 ; Vol. 38, No. 17. pp. 3857-3862.
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abstract = "The electron configuration of a series of low-spin (dicyano){meso-tetrakis(2,4,6-trialkylphenyl)porphyrinato}iron(III) complexes, [Fe(R-TPP)(CN)2]- where R = Me, Et, or iPr, together with the parent [Fe(TPP)(CN)2]-, has been examined in dichloromethane-methanol solution by 1H NMR, 13C NMR, and EPR spectroscopies. While the ferric ion of [Fe(TPP)(CN)2]- has shown a common (dxy)2(dxzdyz)3 configuration, the ferric ions of the alkyl-substituted complexes [Fe(R-TPP)(CN)2]- have exhibited the preference of a less common (dxz,dyz)4(dxy)1 configuration. Spectroscopic characteristics of the complexes in which ferric ions take the (dxz,dyz)4(dxy)1 configuration are (i) axial type EPR spectra, (ii) downfield shifted pyrrole and meta signals in 1H NMR spectra, and (iii) downfield shifted meso-caibon signals in 13C NMR spectra. Occurrence of the less common (dxz,dyz)4(dxy)1 configuration in [Fe(R-TPP)(CN)2]- has been ascribed to the electronic interaction between iron(dπ) and cyanide(pπ*) orbitals. The interaction stabilizes the dπ orbitals and induces (dxzdyz)4(dxy)1 configuration. Since the electron configuration of (dicyano){meso-tetrakis(2,6-dichlorophenyI)porphyrinato}iron(III), [Fe(Cl-TPP)(CN)2]-, which carries bulky electronegative chlorine atoms at the ortho positions, is presented as a common (dxy)2(dxzdyz)3, the less common (dxz,dyz)4(dxy)1 configuration in [Fe(R-TPP)(CN)2]- can be ascribed, at least partially, to the electron-donating ability of the meso-aryl groups.",
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AB - The electron configuration of a series of low-spin (dicyano){meso-tetrakis(2,4,6-trialkylphenyl)porphyrinato}iron(III) complexes, [Fe(R-TPP)(CN)2]- where R = Me, Et, or iPr, together with the parent [Fe(TPP)(CN)2]-, has been examined in dichloromethane-methanol solution by 1H NMR, 13C NMR, and EPR spectroscopies. While the ferric ion of [Fe(TPP)(CN)2]- has shown a common (dxy)2(dxzdyz)3 configuration, the ferric ions of the alkyl-substituted complexes [Fe(R-TPP)(CN)2]- have exhibited the preference of a less common (dxz,dyz)4(dxy)1 configuration. Spectroscopic characteristics of the complexes in which ferric ions take the (dxz,dyz)4(dxy)1 configuration are (i) axial type EPR spectra, (ii) downfield shifted pyrrole and meta signals in 1H NMR spectra, and (iii) downfield shifted meso-caibon signals in 13C NMR spectra. Occurrence of the less common (dxz,dyz)4(dxy)1 configuration in [Fe(R-TPP)(CN)2]- has been ascribed to the electronic interaction between iron(dπ) and cyanide(pπ*) orbitals. The interaction stabilizes the dπ orbitals and induces (dxzdyz)4(dxy)1 configuration. Since the electron configuration of (dicyano){meso-tetrakis(2,6-dichlorophenyI)porphyrinato}iron(III), [Fe(Cl-TPP)(CN)2]-, which carries bulky electronegative chlorine atoms at the ortho positions, is presented as a common (dxy)2(dxzdyz)3, the less common (dxz,dyz)4(dxy)1 configuration in [Fe(R-TPP)(CN)2]- can be ascribed, at least partially, to the electron-donating ability of the meso-aryl groups.

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