Surface-Enhanced Raman Scattering for Redox-Active Adsorbates: Pentaammineosmium(III)/(II) and Pentaammineruthenium(II) Containing Nitrogen Heterocycle Ligands.
PURDUE UNIV LAFAYETTE IN DEPT OF CHEMISTRY
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Surface-Enhanced Raman Scattering SERS for pentaammineosmium III and pentaamminerutheniumII containing pyridine py, pyrazine pz, or 4,4-bipyridine bpy ligands adsorbed at the silver-aqueous interface has been examined as a function of electrode potential to explore vibrational changes associated with electron transfer involving simple adsorbates. SERS was observed for the pyridine complexes despite their lack of an unshared electron pair for surface binding, although more intense spectra were obtained for the pyrzine and bipyridine complexes which contain a remote nitrogen lone pair. SER vibrational bands for metal-ligand and internal ammine modes were observed in addition to those due to heterocycle ring modes. Marked shifts were observed in the frequency of several, vibrational bands for adsorbed OsNH35py and OsNH35pz as the electrode potential was made more negative that are consistent with the reduction fo OsIII to OsII. The potential-dependent concentrations of adsorbed OsIII and OsII as determined using SERS are in good agreement with those obtained from rapid cyclic voltammetry. The bulk-phase Raman spectra exhibit resonance enhancement.
- Atomic and Molecular Physics and Spectroscopy