title: Late first-row transition-metal complexes of texaphyrin.
abstract: The preparation of first-row transition-metal complexes of texaphyrin, a porphyrin-like, monoanionic penta-aza macrocyclic ligand, is reported. Specifically, the synthesis of organic-soluble Mn(II) (1), Co(II) (2), Ni(II) (3), Zn(II) (4), and Fe(III) (5) texaphyrin derivatives and their water-soluble counterparts (6-10) from appropriate metal-free, nonaromatic macrocyclic precursors is described. It was found that metal cations of sufficient reduction potential could act to oxidize the nonaromatic macrocyclic precursor in the course of metal insertion. Complexes were characterized by X-ray diffraction analysis, electrochemistry, flash photolysis, and EPR spectroscopy. The structural and electronic properties of these "expanded porphyrin" complexes are compared with those of analogous porphyrins. Notably, the texaphyrin ligand is found to support the complexation of cations in a lower valence and a higher spin state than do porphyrins. Interactions between the coordinated cation and the ligand pi system appear to contribute to the overall bonding. Texaphyrin complexes of Mn(II), Co(II), and Fe(III) in particular may possess sufficient aqueous stability to permit their use in pharmaceutical applications.
authors.affiliation: Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Sharon
authors.initials: S
authors.lastname: Hannah
authors.forename: Vincent
authors.initials: V
authors.lastname: Lynch
authors.forename: Dirk M
authors.initials: DM
authors.lastname: Guldi
authors.forename: Nikolay
authors.initials: N
authors.lastname: Gerasimchuk
authors.forename: Charles L B
authors.initials: CL
authors.lastname: MacDonald
authors.forename: Darren
authors.initials: D
authors.lastname: Magda
authors.forename: Jonathan L
authors.initials: JL
authors.lastname: Sessler
mesh_terms: D003035:Cobalt / Q000737:chemistry; D004563:Electrochemistry; D004578:Electron Spin Resonance Spectroscopy; D005290:Ferric Compounds / Q000737:chemistry; D008345:Manganese / Q000737:chemistry; D019216:Metals, Heavy / Q000737:chemistry*; D015394:Molecular Structure; D009532:Nickel / Q000737:chemistry; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D011166:Porphyrins / Q000737:chemistry*; D012995:Solubility; D013056:Spectrophotometry, Ultraviolet; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D005290:Ferric Compounds; D019216:Metals, Heavy; D009942:Organometallic Compounds; D011166:Porphyrins; C442892:texaphyrin; D014867:Water; D003035:Cobalt; D008345:Manganese; D009532:Nickel