Chapter 4 - Jacobs University

Chapter 8
Collaborative Work
Chapter 8
Collaborative work
8.1 Electrochemistry
The electrochemical studies on polyanions 1, 3 and 5 were performed by the group of Professor
L. Nadjo from the Laboratoire de Chimie Physique, UMR 8000, CNRS, Equipe d’Electrochimie
et Photoe´lectrochimie, Université Paris-Sud, Bâtiment 420, 91405 Orsay Cedex, France. For
more detailed info please check Electrochem. Comm. 2005, 7, 841; Chem. Eur. J. 2008, 14, 1186
and Angew. Chem. Int. Ed. 2008, 47, 793 inAppendix.
8.1.1 - Electrochemistry of [Cu 20 Cl(OH) 24 (H 2 O) 12 (P 8 W 48 O 184 )] 25- (1)
The polyanion 1 was studied by cyclic voltammetry and controlled potential coulometry in pH 0
and pH 5 media. In the two media, the cyclic voltammograms are dominated by the current
intensities of processes attributed to the reduction of Cu 2+ centers. In the pH 0 medium, the first
two waves of the lacunary heteropolyanion are practically engulfed in the tail of the overall l
copper reduction process. A much better separation is obtained in the pH 5 medium and is
attributed to the large sensitivity of tungsten centers to pH variations. The supramolecular
complex shows a strong catalytic activity towards nitrate and nitrite. Comparison with the
activity per copper atom of previously studied copper-substituted heteropolyanions indicates the
supramolecular complex to be significantly more efficient, a feature that reinforces the notion
that accumulation of transition metals within polyoxometalates should be beneficial for the
relevant catalytic processes.
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