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Benzoannelation Stabilizes the dxy1 State of Low-Spin Iron(III) Porphyrinates.

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Title: Benzoannelation Stabilizes the dxy1 State of Low-Spin Iron(III) Porphyrinates.
Authors: Ikeue, Takahisa1, Handa, Makoto1, Chamberlin, Adam2, Ghosh, Abhik2, Ongayi, Owendi3, Vicente, M. Graça H.3, Ikezaki, Akira4, Nakamura, Mikio5
Source: Inorganic Chemistry. 4/18/2011, Vol. 50 Issue 8, p3567-3581. 15p.
Subjects: Iron compounds, Electron paramagnetic resonance spectroscopy, Density functionals, Proton magnetic resonance spectroscopy, Porphyrins, Band gaps, Isomers
Abstract: A series of low-spin, six-coordinate complexes [Fe(TBzTArP)L2]X (1) and [Fe(TBuTArP)L2]X (2) (X = Cl−, BF4−, or Bu4N+), where the axial ligands (L) are HIm, 1-MeIm, DMAP, 4-MeOPy, 4-MePy, Py, and CN−, were prepared. The electronic structures of these complexes were examined by 1H NMR and electron paramagnetic resonance (EPR) spectroscopy as well as density functional theory (DFT) calculations. In spite of the fact that almost all of the bis(HIm), bis(1-MeIm), and bis(DMAP) complexes reported previously (including 2) adopt the (dxy)2(dxz, dyz)3 ground state, the corresponding complexes of 1 show the (dxz, dyz)4(dxy)1 ground state at ambient temperature. At lower temperature, the electronic ground state of the HIm, 1-MeIm, and DMAP complexes of 1 changes to the common (dxy)2(dxz, dyz)3 ground state. All of the other complexes of 1 and 2 carrying 4-MeOPy, 4-MePy, Py, and CN− maintain the (dxz, dyz)4(dxy)1 ground state in the NMR temperature range, i.e., 298−173 K. The EPR spectra taken at 4.2 K are fully consistent with the NMR results because the HIm and 1-MeIm complexes of 1 and 2 adopt the (dxy)2(dxz, dyz)3 ground state, as revealed by the rhombic-type spectra. The DMAP complex of 1 exists as a mixture of two electron-configurational isomers. All of the other complexes adopt the (dxz, dyz)4(dxy)1 ground state, as revealed by the axial-type spectra. Among the complexes adopting the (dxz, dyz)4(dxy)1 ground state, the energy gap between the dxy and dπ orbitals in 1 is always larger than that of the corresponding complex of 2. Thus, it is clear that the benzoannelation of the porphyrin ring stabilizes the (dxz, dyz)4(dxy)1 ground state. The DFT calculation of the bis(Py) complex of analogous iron(III) porphyrinate, [Fe(TPTBzP)(Py)2]+, suggests that the (dxz, dyz)4(dxy)1 state is more stable than the (dxy)2(dxz, dyz)3 state in both ruffled and saddled conformations. The lowest-energy states in the two conformers are so close in energy that their ordering is reversed depending on the calculation methods applied. On the basis of the spectroscopic and theoretical results, we concluded that 1, having 4-MeOPy, 4-MePy, and Py as axial ligands, exists as an equilibrium mixture of saddled and ruffled isomers both of which adopt the (dxz, dyz)4(dxy)1 ground state. The stability of the (dxz, dyz)4(dxy)1 ground state is ascribed to the strong bonding interaction between the iron dxy and porphyrin a1u orbitals in the saddled conformer caused by the high energy of the a1u highest occupied molecular orbital in TBzTArP. Similarly, a bonding interaction occurs between the dxy and a2u orbitals in the ruffled conformer. In addition, the bonding interaction of the dπ orbitals with the low-lying lowest unoccupied molecular orbital, which is an inherent characteristic of TBzTArP, can also contribute to stabilization of the (dxz, dyz)4(dxy)1 ground state. [ABSTRACT FROM AUTHOR]
Copyright of Inorganic Chemistry is the property of American Chemical Society and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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  Data: Benzoannelation Stabilizes the d<subscript>xy</subscript><superscript>1</superscript> State of Low-Spin Iron(III) Porphyrinates.
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  Data: <searchLink fieldCode="AR" term="%22Ikeue%2C+Takahisa%22">Ikeue, Takahisa</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Handa%2C+Makoto%22">Handa, Makoto</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Chamberlin%2C+Adam%22">Chamberlin, Adam</searchLink><relatesTo>2</relatesTo><br /><searchLink fieldCode="AR" term="%22Ghosh%2C+Abhik%22">Ghosh, Abhik</searchLink><relatesTo>2</relatesTo><br /><searchLink fieldCode="AR" term="%22Ongayi%2C+Owendi%22">Ongayi, Owendi</searchLink><relatesTo>3</relatesTo><br /><searchLink fieldCode="AR" term="%22Vicente%2C+M%2E+Graça+H%2E%22">Vicente, M. Graça H.</searchLink><relatesTo>3</relatesTo><br /><searchLink fieldCode="AR" term="%22Ikezaki%2C+Akira%22">Ikezaki, Akira</searchLink><relatesTo>4</relatesTo><br /><searchLink fieldCode="AR" term="%22Nakamura%2C+Mikio%22">Nakamura, Mikio</searchLink><relatesTo>5</relatesTo>
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  Data: <searchLink fieldCode="JN" term="%22Inorganic+Chemistry%22">Inorganic Chemistry</searchLink>. 4/18/2011, Vol. 50 Issue 8, p3567-3581. 15p.
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  Data: <searchLink fieldCode="DE" term="%22Iron+compounds%22">Iron compounds</searchLink><br /><searchLink fieldCode="DE" term="%22Electron+paramagnetic+resonance+spectroscopy%22">Electron paramagnetic resonance spectroscopy</searchLink><br /><searchLink fieldCode="DE" term="%22Density+functionals%22">Density functionals</searchLink><br /><searchLink fieldCode="DE" term="%22Proton+magnetic+resonance+spectroscopy%22">Proton magnetic resonance spectroscopy</searchLink><br /><searchLink fieldCode="DE" term="%22Porphyrins%22">Porphyrins</searchLink><br /><searchLink fieldCode="DE" term="%22Band+gaps%22">Band gaps</searchLink><br /><searchLink fieldCode="DE" term="%22Isomers%22">Isomers</searchLink>
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  Data: A series of low-spin, six-coordinate complexes [Fe(TBzTArP)L2]X (1) and [Fe(TBuTArP)L2]X (2) (X = Cl−, BF4−, or Bu4N+), where the axial ligands (L) are HIm, 1-MeIm, DMAP, 4-MeOPy, 4-MePy, Py, and CN−, were prepared. The electronic structures of these complexes were examined by 1H NMR and electron paramagnetic resonance (EPR) spectroscopy as well as density functional theory (DFT) calculations. In spite of the fact that almost all of the bis(HIm), bis(1-MeIm), and bis(DMAP) complexes reported previously (including 2) adopt the (dxy)2(dxz, dyz)3 ground state, the corresponding complexes of 1 show the (dxz, dyz)4(dxy)1 ground state at ambient temperature. At lower temperature, the electronic ground state of the HIm, 1-MeIm, and DMAP complexes of 1 changes to the common (dxy)2(dxz, dyz)3 ground state. All of the other complexes of 1 and 2 carrying 4-MeOPy, 4-MePy, Py, and CN− maintain the (dxz, dyz)4(dxy)1 ground state in the NMR temperature range, i.e., 298−173 K. The EPR spectra taken at 4.2 K are fully consistent with the NMR results because the HIm and 1-MeIm complexes of 1 and 2 adopt the (dxy)2(dxz, dyz)3 ground state, as revealed by the rhombic-type spectra. The DMAP complex of 1 exists as a mixture of two electron-configurational isomers. All of the other complexes adopt the (dxz, dyz)4(dxy)1 ground state, as revealed by the axial-type spectra. Among the complexes adopting the (dxz, dyz)4(dxy)1 ground state, the energy gap between the dxy and dπ orbitals in 1 is always larger than that of the corresponding complex of 2. Thus, it is clear that the benzoannelation of the porphyrin ring stabilizes the (dxz, dyz)4(dxy)1 ground state. The DFT calculation of the bis(Py) complex of analogous iron(III) porphyrinate, [Fe(TPTBzP)(Py)2]+, suggests that the (dxz, dyz)4(dxy)1 state is more stable than the (dxy)2(dxz, dyz)3 state in both ruffled and saddled conformations. The lowest-energy states in the two conformers are so close in energy that their ordering is reversed depending on the calculation methods applied. On the basis of the spectroscopic and theoretical results, we concluded that 1, having 4-MeOPy, 4-MePy, and Py as axial ligands, exists as an equilibrium mixture of saddled and ruffled isomers both of which adopt the (dxz, dyz)4(dxy)1 ground state. The stability of the (dxz, dyz)4(dxy)1 ground state is ascribed to the strong bonding interaction between the iron dxy and porphyrin a1u orbitals in the saddled conformer caused by the high energy of the a1u highest occupied molecular orbital in TBzTArP. Similarly, a bonding interaction occurs between the dxy and a2u orbitals in the ruffled conformer. In addition, the bonding interaction of the dπ orbitals with the low-lying lowest unoccupied molecular orbital, which is an inherent characteristic of TBzTArP, can also contribute to stabilization of the (dxz, dyz)4(dxy)1 ground state. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of Inorganic Chemistry is the property of American Chemical Society and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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      – Type: doi
        Value: 10.1021/ic1024873
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      – Code: eng
        Text: English
    PhysicalDescription:
      Pagination:
        PageCount: 15
        StartPage: 3567
    Subjects:
      – SubjectFull: Iron compounds
        Type: general
      – SubjectFull: Electron paramagnetic resonance spectroscopy
        Type: general
      – SubjectFull: Density functionals
        Type: general
      – SubjectFull: Proton magnetic resonance spectroscopy
        Type: general
      – SubjectFull: Porphyrins
        Type: general
      – SubjectFull: Band gaps
        Type: general
      – SubjectFull: Isomers
        Type: general
    Titles:
      – TitleFull: Benzoannelation Stabilizes the dxy1 State of Low-Spin Iron(III) Porphyrinates.
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            NameFull: Chamberlin, Adam
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              Text: 4/18/2011
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              Y: 2011
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