Electronic structures of five-coordinate iron(III) porphyrin complexes with highly ruffled porphyrin ring

Takanori Sakai, Yoshiki Ohgo, Akito Hoshino, Takahisa Ikeue, Takashi Saitoh, Masashi Takahashi, Mikio Nakamura

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Abstract

The spin states of the iron(III) complexes with a highly ruffled porphyrin ring, [Fe(TEtPrP)X] where X = F-, Cl-, Br-, l-, and ClO4-, have been examined by 1H NMR, 13C NMR, EPR, and Mössbauer spectroscopy. While the F-, Cl-, and Br- complexes adopt a high-spin (S = 5/2) state, the l- complex exhibits an admixed intermediate-spin (S = 5/2, 3/2) state in CD2Cl2 solution. The l- complex shows, however, a quite pure high-spin state in toluene solution as well as in the solid. The results contrast those of highly saddled [Fe(OETPP)X] where the l- complex exhibits an essentially pure intermediate-spin state both in solution and in the solid. In contrast to the halide-ligated complexes, the ClO4- complex shows a quite pure intermediate-spin state. The 13C NMR spectra of [Fe(TEtPrP)-ClO4] are characterized by the downfield and upfield shifts of the meso and pyrrole-α carbon signals, respectively: δ(meso) = +342 and δ(α-py) = -287 ppm at 298 K. The data indicate that the meso carbon atoms of [Fe-(TEtPrP)ClO4] have considerable amounts of positive spin, which in turn indicate that the iron has an unpaired electron in the dxy orbital; the unpaired electron in the dxy orbital is delocalized to the meso positions due to the iron (dxy)-porphyrin(a2u) interaction. Similar results have been obtained in analogous [Fe(TiPrP)X] though the intermediate-spin character of [Fe(TiPrP)X] is much larger than that of the corresponding [Fe(TEtPrP)X]. On the basis of these results, we have concluded that the highly ruffled intermediate-spin complexes such as [Fe(TEtPrP)-ClO 4] and [Fe(TiPrP)ClO4] adopt a novel (d xz, dyz)3(dxy)1(dz 2)1 electron configuration; the electron configuration of the intermediate-spin complexes reported previously is believed to be (d xy)2(dxz, dyz)2(d z2)1.

Original languageEnglish
Pages (from-to)5034-5043
Number of pages10
JournalInorganic Chemistry
Volume43
Issue number16
DOIs
Publication statusPublished - 2004 Aug 9

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Porphyrins
porphyrins
Electronic structure
Iron
electronic structure
iron
rings
Electrons
Nuclear magnetic resonance
Carbon
Pyrroles
Toluene
nuclear magnetic resonance
Paramagnetic resonance
electrons
perchlorate
Spectroscopy
orbitals
Atoms
carbon

ASJC Scopus subject areas

  • Inorganic Chemistry

Cite this

Sakai, T., Ohgo, Y., Hoshino, A., Ikeue, T., Saitoh, T., Takahashi, M., & Nakamura, M. (2004). Electronic structures of five-coordinate iron(III) porphyrin complexes with highly ruffled porphyrin ring. Inorganic Chemistry, 43(16), 5034-5043. https://doi.org/10.1021/ic049825q

Electronic structures of five-coordinate iron(III) porphyrin complexes with highly ruffled porphyrin ring. / Sakai, Takanori; Ohgo, Yoshiki; Hoshino, Akito; Ikeue, Takahisa; Saitoh, Takashi; Takahashi, Masashi; Nakamura, Mikio.

In: Inorganic Chemistry, Vol. 43, No. 16, 09.08.2004, p. 5034-5043.

Research output: Contribution to journalArticle

Sakai, T, Ohgo, Y, Hoshino, A, Ikeue, T, Saitoh, T, Takahashi, M & Nakamura, M 2004, 'Electronic structures of five-coordinate iron(III) porphyrin complexes with highly ruffled porphyrin ring', Inorganic Chemistry, vol. 43, no. 16, pp. 5034-5043. https://doi.org/10.1021/ic049825q
Sakai, Takanori ; Ohgo, Yoshiki ; Hoshino, Akito ; Ikeue, Takahisa ; Saitoh, Takashi ; Takahashi, Masashi ; Nakamura, Mikio. / Electronic structures of five-coordinate iron(III) porphyrin complexes with highly ruffled porphyrin ring. In: Inorganic Chemistry. 2004 ; Vol. 43, No. 16. pp. 5034-5043.
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abstract = "The spin states of the iron(III) complexes with a highly ruffled porphyrin ring, [Fe(TEtPrP)X] where X = F-, Cl-, Br-, l-, and ClO4-, have been examined by 1H NMR, 13C NMR, EPR, and M{\"o}ssbauer spectroscopy. While the F-, Cl-, and Br- complexes adopt a high-spin (S = 5/2) state, the l- complex exhibits an admixed intermediate-spin (S = 5/2, 3/2) state in CD2Cl2 solution. The l- complex shows, however, a quite pure high-spin state in toluene solution as well as in the solid. The results contrast those of highly saddled [Fe(OETPP)X] where the l- complex exhibits an essentially pure intermediate-spin state both in solution and in the solid. In contrast to the halide-ligated complexes, the ClO4- complex shows a quite pure intermediate-spin state. The 13C NMR spectra of [Fe(TEtPrP)-ClO4] are characterized by the downfield and upfield shifts of the meso and pyrrole-α carbon signals, respectively: δ(meso) = +342 and δ(α-py) = -287 ppm at 298 K. The data indicate that the meso carbon atoms of [Fe-(TEtPrP)ClO4] have considerable amounts of positive spin, which in turn indicate that the iron has an unpaired electron in the dxy orbital; the unpaired electron in the dxy orbital is delocalized to the meso positions due to the iron (dxy)-porphyrin(a2u) interaction. Similar results have been obtained in analogous [Fe(TiPrP)X] though the intermediate-spin character of [Fe(TiPrP)X] is much larger than that of the corresponding [Fe(TEtPrP)X]. On the basis of these results, we have concluded that the highly ruffled intermediate-spin complexes such as [Fe(TEtPrP)-ClO 4] and [Fe(TiPrP)ClO4] adopt a novel (d xz, dyz)3(dxy)1(dz 2)1 electron configuration; the electron configuration of the intermediate-spin complexes reported previously is believed to be (d xy)2(dxz, dyz)2(d z2)1.",
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T1 - Electronic structures of five-coordinate iron(III) porphyrin complexes with highly ruffled porphyrin ring

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AU - Saitoh, Takashi

AU - Takahashi, Masashi

AU - Nakamura, Mikio

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N2 - The spin states of the iron(III) complexes with a highly ruffled porphyrin ring, [Fe(TEtPrP)X] where X = F-, Cl-, Br-, l-, and ClO4-, have been examined by 1H NMR, 13C NMR, EPR, and Mössbauer spectroscopy. While the F-, Cl-, and Br- complexes adopt a high-spin (S = 5/2) state, the l- complex exhibits an admixed intermediate-spin (S = 5/2, 3/2) state in CD2Cl2 solution. The l- complex shows, however, a quite pure high-spin state in toluene solution as well as in the solid. The results contrast those of highly saddled [Fe(OETPP)X] where the l- complex exhibits an essentially pure intermediate-spin state both in solution and in the solid. In contrast to the halide-ligated complexes, the ClO4- complex shows a quite pure intermediate-spin state. The 13C NMR spectra of [Fe(TEtPrP)-ClO4] are characterized by the downfield and upfield shifts of the meso and pyrrole-α carbon signals, respectively: δ(meso) = +342 and δ(α-py) = -287 ppm at 298 K. The data indicate that the meso carbon atoms of [Fe-(TEtPrP)ClO4] have considerable amounts of positive spin, which in turn indicate that the iron has an unpaired electron in the dxy orbital; the unpaired electron in the dxy orbital is delocalized to the meso positions due to the iron (dxy)-porphyrin(a2u) interaction. Similar results have been obtained in analogous [Fe(TiPrP)X] though the intermediate-spin character of [Fe(TiPrP)X] is much larger than that of the corresponding [Fe(TEtPrP)X]. On the basis of these results, we have concluded that the highly ruffled intermediate-spin complexes such as [Fe(TEtPrP)-ClO 4] and [Fe(TiPrP)ClO4] adopt a novel (d xz, dyz)3(dxy)1(dz 2)1 electron configuration; the electron configuration of the intermediate-spin complexes reported previously is believed to be (d xy)2(dxz, dyz)2(d z2)1.

AB - The spin states of the iron(III) complexes with a highly ruffled porphyrin ring, [Fe(TEtPrP)X] where X = F-, Cl-, Br-, l-, and ClO4-, have been examined by 1H NMR, 13C NMR, EPR, and Mössbauer spectroscopy. While the F-, Cl-, and Br- complexes adopt a high-spin (S = 5/2) state, the l- complex exhibits an admixed intermediate-spin (S = 5/2, 3/2) state in CD2Cl2 solution. The l- complex shows, however, a quite pure high-spin state in toluene solution as well as in the solid. The results contrast those of highly saddled [Fe(OETPP)X] where the l- complex exhibits an essentially pure intermediate-spin state both in solution and in the solid. In contrast to the halide-ligated complexes, the ClO4- complex shows a quite pure intermediate-spin state. The 13C NMR spectra of [Fe(TEtPrP)-ClO4] are characterized by the downfield and upfield shifts of the meso and pyrrole-α carbon signals, respectively: δ(meso) = +342 and δ(α-py) = -287 ppm at 298 K. The data indicate that the meso carbon atoms of [Fe-(TEtPrP)ClO4] have considerable amounts of positive spin, which in turn indicate that the iron has an unpaired electron in the dxy orbital; the unpaired electron in the dxy orbital is delocalized to the meso positions due to the iron (dxy)-porphyrin(a2u) interaction. Similar results have been obtained in analogous [Fe(TiPrP)X] though the intermediate-spin character of [Fe(TiPrP)X] is much larger than that of the corresponding [Fe(TEtPrP)X]. On the basis of these results, we have concluded that the highly ruffled intermediate-spin complexes such as [Fe(TEtPrP)-ClO 4] and [Fe(TiPrP)ClO4] adopt a novel (d xz, dyz)3(dxy)1(dz 2)1 electron configuration; the electron configuration of the intermediate-spin complexes reported previously is believed to be (d xy)2(dxz, dyz)2(d z2)1.

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