Resonance Raman spectra of monolayers of transition metal phthalocyanines reveal specific interaction with the support. To elucidate its mechanism, Raman spectra of zinc phthalocyanine monolayers were studied. The analysis was based largely on the results of MNDO calculations. Calculated wavenumbers turned out to be in good agreement with the experimental results. It seems plausible that the a-nitrogen atoms dominate the interaction with the support. Calculation results also show that the usually assumed D,, geometry does not represent the true energy minimum but must be considered as the 'mean' of two mesomeric forms.
0, reduction in an acid medium has been investigated on a transition metal macrocycle, CoNPc(l,2), impregnated on a carbon black support with a high dibutylphthalate adsorption value, using a rotating disk electrode and voltammetry techniques described previously, combined with X-ray photoelectron spectroscopy measurements. Optimal activity was found for a bilayer coverage (n = 2) at 17%-B% w/w loading. Heat treatment seems to be beneficial for n 6 3: it increases the overall number N of exchanged electrons and improves the electrode wetting. For the most active samples, mixed Co(II1/cdIIIl valencies were displayed.
Raman spectra of zinc phthalocyanine monolayers, adsorbed on gold and on glassy carbon surfaces (electrodes), are presented. These spectra have been recorded with the electrodes inside and outside an electrochemical cell filled with an aqueous electrolyte. A confocal Raman microspectrometer was used. It was demonstrated that, because this spectrometer uses low laser intensities, no damage of the monolayer occurred. The results show that the interaction of the phthalocyanine molecule with gold differs from that with glassy carbon. Because the laser excitation wavelength (660 nm) coincides with a UV-visible absorption band (Q band), a strong resonance-enhanced Raman spectrum was obtained. No signs of surface enhancement (surface-enhanced Raman scattering) effects were detected.
INTRODUCI'IONTransition metal phthalocyanines, especially those with iron and cobalt, are interesting catalysts for the electroreduction of molecular oxygen [l-5]. The redox properties of these compounds adsorbed on carbon supports have been reported [2-61. It has been shown that the interaction between adsorbate and support influences the electrocatalytic activity [3,6], i.e. different carbon supports result in 0022-0728/92/$05.00 0 1992 -Elsevier Sequoia S.A. All rights reserved
The high resolution He 584 8, photoelectron spectra of ten fluorine-substituted diazabenzenes are presented. By means of fluorine substitution the analysis of the photoelectron spectra of the parent compounds can be made more definite. "Lone-pair" ionization potentials are shown to correlate well with data calculated by a modified and iterative version of the extended Hiickel method.
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