ANYL 139 |
| Electrochemical and surface spectroscopic techniques (surface-enhanced Raman spectroscopy, SERS, cyclic voltammetric technique, thin-layer spectroelectrochemical technique and the UV visible absorption spectroscopy) are used to investigate the pH dependent aggregation state of Iron(III) tetrakis(N,N,N-trimethyl-4-aniliniumyl) porphyrin (FeTAP), as well as its reductive electrochemistry. UV-Visible absorption spectroscopy at pH 3 indicates that FeTAP exists as the monomer while at pH 11.5, the porphyrin exists as the dimer. Voltammetric studies on Ag electrode indicate a reductive peak at –1.0 V at pH 3; reductive peaks at -0.40 V, and -0.70 V on Ag electrode at pH 11.5. Potential-dependent shifts in the 398 nm UV/vis absorbance band to 424nm at –0.8V on a gold minigrid electrode indicate that reduction of the porphyrin central metal from FeIII to FeII occurs at this potential. FeIII peak at 406 nm characterizes UV-vis spectrum of FeTAP at pH 11.5. Potential reduction of FeTAP at this pH is characterized by the emergence of persistent FeII peak at 442 nm. Both peaks remain in the UV-vis spectra. Finally, the symmetric Fe-O-Fe stretching vibration for the u-oxo dimer adsorbed on a silver electrode is assigned to the 420 cm-1 band, which is observed in the SERS spectra of FeTAP at pH 11.5. Shifts in the wavenumber of the oxidation state marker band allowed for the determination of the oxidation state of the adsorbed FeTAP from the potential dependent SERS studies. |
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General Papers
7:00 PM-9:00 PM, Sunday, 28 August 2005 Washington DC Convention Center -- Hall A, Poster
Division of Analytical Chemistry |