TY - JOUR
T1 - Electron configuration of ferric ions in low-spin (dicyano)(meso-tetraarylporphyrinato)iron(III) complexes
AU - Nakamura, Mikio
AU - Ikeue, Takahisa
AU - Ikezaki, Akira
AU - Ohgo, Yoshiki
AU - Fujii, Hiroshi
PY - 1999
Y1 - 1999
N2 - 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.
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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U2 - 10.1021/ic990328x
DO - 10.1021/ic990328x
M3 - Article
AN - SCOPUS:0001466680
SN - 0020-1669
VL - 38
SP - 3857
EP - 3862
JO - Inorganic Chemistry
JF - Inorganic Chemistry
IS - 17
ER -