Surface-Enhanced Raman Spectroscopic (SERS and FT-SERS) Investigation of the Complex Ion [Fe2(CN)10L]6- (L = 4,4'-Bipyridine and Pyrazine) Adsorbed on Silver and Gold Electrodes

  • Rubim J
  • Temperini M
  • Corio P
 et al. 
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Abstract

The spectroelectrochem. behavior of binuclear [Fe2(CN)10L]6-, where L is the bridging ligands 4,4'-bipyridine (bipy) or pyrazine (pz), was studied by surface-enhanced Raman spectroscopy, in the visible and in the near-IR, on silver and gold electrodes. The vibrational frequencies of bipy were the same whether II or III was the oxidn. state of the metal ions. However, shifts to higher energies of the nCN bands for both complexes were obsd. as the oxidn. states of the metal ions changed from II to III. The SERS frequencies were also higher than the values obsd. in the normal Raman spectra of the complexes in soln. For potentials more neg. than -1.2 V, the ligands were reduced and the SER and FT-SER spectra presented marked changes with the appearance of new bands. In the case where bipy was the bridge ligand, vibrational modes involving the bridge ligand and the CN or Fe-CN bonds were enhanced while for pz only the latter vibrational modes were obsd. This unlike behavior was assigned to differences in the structure of the ligand in relation to metal surface. The dependence of nCN frequency on the applied potential showed that this mode is enhanced by a charge transfer mechanism, ligand (CN) to metal, while the dependence of the SERS intensity on the applied potential and laser excitation energy showed that a charge transfer mechanism, metal to a p* orbital of bipy ligand, is responsible for the enhancement of the bipy vibrational modes. Through the use of the data obtained from the plot of Vmax (potential of max. SERS intensity) vs. laser energy, an energy diagram for the adsorbed [Fe2(CN)10bipy]6- complex is proposed. [on SciFinder (R)]

Author-supplied keywords

  • adsorbed iron bipyridine pyrazine electrode Raman
  • gold electrode iron bipyridine pyrazine Raman
  • iron cyano bipyridine pyrazine electrode Raman
  • silver electrode iron bipyridine pyrazine Raman

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Authors

  • J C Rubim

  • M L a Temperini

  • P Corio

  • O Sala

  • a H Jubert

  • M E Chacon-Villalba

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