Electronic and Magnetic Structures of Iron Porphyrin Complexes

The following sections are included:

• I. Introduction

• II. NMR and EPR Methods to Determine the Electronic Structures

  • A. Orbital Interactions

  • B. NMR Spectroscopy

    • 1. ¹H NMR Spectroscopy

    • 2. ¹³C NMR Spectroscopy

  • C. EPR Spectroscopy

• III. Low-Spin Iron(III) Porphyrins

  • A. General Considerations

  • B. Factors Affecting the Electronic Ground States

    • 1. Axial Ligands

    • 2. Electronic Effects of Peripheral Substituents

    • 3. Deformation of the Porphyrin Ring

      • a. Ruffled Deformation

      • b. Saddled Deformation

    • 4. Solvent Effects

  • C. Low-Spin Complexes with a Rare Electronic Ground State

    • 1. Bis-Imidazole Complexes that Adopt the (d_xz′ d_yz)⁴(d_xy)¹ Ground State

    • 2. A Bis-Tert-Butylisocyanide Complex Adopting the (d_xy)²(d_xz′ d_yz)₃ Ground State

• IV. Mixed High-Spin and Intermediate-Spin Complexes

  • A. General Considerations

  • B. Formation of Pure Intermediate-Spin Complexes

    • 1. Axial Ligands with Extremely Weak Field Strength

      • a. Magnetochemical Series

      • b. Four-Coordinate Iron(III) Porphyrin Cation

    • 2. Deformation of the Porphyrin Ring

      • a. Ruffled Deformation

        • i. Five-Coordinate Complexes

        • ii. Six-Coordinate Complexes

      • b. Saddled Deformation

        • i. Five-Coordinate Complexes

        • ii. Six-Coordinate Complexes

  • C. Electronic Ground State in Intermediate-Spin Complexes

• V. Spin Crossover in Iron(III) Porphyrins

  • A. General Considerations

  • B. Spin Crossover Between S = 3/2 and S = 1/2

    • 1. [Fe(OETPP)L₂]⁺

    • 2. [Fe(OMTPP)L₂]⁺ and [Fe(TBTXP)L₂]⁺

    • 3. [Fe(MAzP)L₂]^± and [Fe(OEP)L₂]^±

    • 4. Structural Consequences of Spin Crossover

  • C. Spin Crossover Between S = 3/2 and S = 5/2

    • 1. Monoaqua Complexes of Saddled Porphyrins

    • 2. Monoazide Complexes

  • D. Spin Crossover in Monoimidazole Complexes

    • 1. [Fe(TMP)L]⁺ and [Fe(TMTMP)L]⁺

    • 2. [Fe(OETPP)L]⁺

• VI. Oxidized Products of Iron(III) Porphyrin Complexes

  • A. One-Electron-Oxidized Products

    • 1. Iron(III) Porphyrin Cation Radicals

      • a. High-Spin Iron(III) Porphyrin Cation Radicals

      • b. Mixed High-Spin and Intermediate-Spin Iron(III) Porphyrin Cation Radicals

      • c. Low-Spin Iron(III) Porphyrin Cation Radicals

        • i. Iron(III) with the (d_xy)²(d_xz′ d_yz)³ Electron Configuration

        • ii. Iron(III) with the (d_xz′ d_yz)⁴(d_xy)¹ Electron Configuration

    • 2. Iron(IV) Porphyrin Complexes

      • a. Iron(IV) porphyrins with an Fe^IV=O bond

      • b. Iron(IV) porphyrins without an Fe=O bond

  • B. Two-Electron-Oxidized Products of Iron(III) Porphyrins

    • 1. Oxoiron(IV) Porphyrin Cation Radicals

    • 2. Iron(III) Porphyrin N-Oxides

    • 3. Iron(III) Porphyrin Dications

    • 4. Iron(V) Porphyrins

• VII. Acknowledgments

• VIII. References