title: Electronic ground states of low-spin iron(III) porphyrinoids.
abstract: Six-coordinate low-spin iron(III) porphyrinates adopt either common (d(xy))(2)(d(xz),d(yz))(3) or less common (d(xz),d(yz))(4)(d(xy))(1) ground state. In this review article, three major factors that affect the electronic ground state have been examined. They are (i) nature of the axial ligand, (ii) electronic effect of peripheral substituents, and (iii) deformation of porphyrin ring. On the basis of the (1)H NMR, (13)C NMR, and EPR data, it is now clear that (i) the axial ligands with low-lying pi* orbitals such as tert-butylisocyanide and 4-cyanopyridine, (ii) the electron donating groups at the meso-carbon atoms, and (iii) the ruffled deformation of porphyrin ring stabilize the (d(xz),d(yz))(4)(d(xy))(1) ground state. By manipulating these factors, we are able to prepare various low-spin iron(III) porphyrinates with unusual electronic structures such as bis(imidazole) complexes with the (d(xz),d(yz))(4)(d(xy))(1) ground state or bis(tert-butylisocyanide) complexes with the (d(xy))(2)(d(xz),d(yz))(3) ground state; bis(imidazole) and bis(tert-butylisocyanide) complexes usually adopt the (d(xy))(2)(d(xz),d(yz))(3) and (d(xz),d(yz))(4)(d(xy))(1) ground state, respectively.
authors.affiliation: Department of Chemistry, Faculty of Medicine, Toho University, Ota-ku, Tokyo 143-8540, Japan. mnakamu@med.toho-u.ac.jp
authors.forename: Mikio
authors.initials: M
authors.lastname: Nakamura
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Ohgo
authors.forename: Akira
authors.initials: A
authors.lastname: Ikezaki
mesh_terms: D002384:Catalysis; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D006427:Hemin / Q000737:chemistry* / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008954:Models, Biological; D008958:Models, Molecular; D015394:Molecular Structure
chemical_list: D006427:Hemin; D003577:Cytochrome P-450 Enzyme System