Late first-row transition-metal complexes of texaphyrin.
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.
Hannah
Sharon
S
Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712, USA.
Lynch
Vincent
V
Guldi
Dirk M
DM
Gerasimchuk
Nikolay
N
MacDonald
Charles L B
CL
Magda
Darren
D
Sessler
Jonathan L
JL
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
D005290:Ferric Compounds; D019216:Metals, Heavy; D009942:Organometallic Compounds; D011166:Porphyrins; C442892:texaphyrin; D014867:Water; D003035:Cobalt; D008345:Manganese; D009532:Nickel