Ligand-aided photoreduction of iron-porphyrin complexes probed by resonance Raman spectroscopy
Photoreduction has been observed for the first time for an iron porphyrin with a biologically relevant axial ligand by using resonance Raman (RR) spectroscopy (for Fe/sup III/(OEP)(2-MeIm), OEP = octaethylporphyrin and 2-MeIm = 2-methylimidazole). The action spectrum for the photoreduction obtained by visible absorption spectra exhibited a broad maximum around 420-460 nm, which was appreciably shifted from the Soret band of Fe/sup III/(OEP)(2-MeIm) at 395 nm. Similar photoreduction was observed for Fe/sup III/(OEP)(1,2-Me/sub 2/Im) (1,2-Me/sub 2/Im = 1,2-dimethylimidazole) but not for Fe/sup III/(OEP)L/sub 2/ (L = imidazole and 1-methylimidazole) and Fe/sup III/(OEP)X (X = F, Cl, Br, I, and ClO/sub 4/). The coincidence of the RR spectrum of the photoreduced species with that of the ferrous porphyrin rules out the possibility of ring reduction to a porphyrin anion radical or chlorin. The dependence of the photoreduction on the concentration of 2-MeIm suggested that the ligand-free Fe/sup II/(OEP) is a likely intermediate and thus that the light-induced charge transfer from the axial ligand to the iron ion is the primary process of photoreduction.
- Research Organization:
- Jikei Univ. School of Medicine, Tokyo, Japan
- OSTI ID:
- 5889860
- Journal Information:
- J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 109:19; ISSN JACSA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400500* -- Photochemistry
ABSORPTION SPECTROSCOPY
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
CHEMISTRY
COMPLEXES
DATA
EFFICIENCY
EXPERIMENTAL DATA
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
INFORMATION
IRON COMPLEXES
LASER SPECTROSCOPY
LIGANDS
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOCHEMISTRY
PORPHYRINS
QUANTITY RATIO
QUANTUM EFFICIENCY
RAMAN SPECTROSCOPY
REACTION INTERMEDIATES
REDUCTION
SPECTRA
SPECTROSCOPY
TRANSITION ELEMENT COMPLEXES
VISIBLE SPECTRA