Some Evidence for the Formation of an Azo Bond during the Electroreduction of Diazonium Salts on Au Substrates

RICCI, ALEJANDRA M.; MENDEZ DE LEO, LUCILA PAULA; WILLIAMS, FEDERICO J.; CALVO, ERNESTO J.

Chemphyschem

WILEY-V C H VERLAG GMBH

Año: 2012 vol. 13 p. 2119 - 2127

1439-4235

Molecular films obtained by electrochemical reduction of diazoniuim tetrafluoroborate salts [4-carboxybenzene (PhCOOH) and 4-amino-(2,3,5,6-tetrafluoro)-carboxybenzene (PhF4COOH)] on Au substrates and post-functionalization with an osmium pyridil-bipyridine complex are studied by a combination of Xray photoelectron (XPS) and polarization-modulation infrared reflection absorption spectroscopy (PM-IRRAS). The spectroscopic evidence suggests the formation of N=N bonds tethering the complexes to Au&&ok?&&. The surface coverage of the azo-bonded osmium complexes strongly depends on the electrode potential. The resulting tethered osmium redox centres were characterized by cyclic voltammetry and impedance spectroscopy. Similar electron transfer-rate constants were measured for both fluorinated and non fluorinated benzenelinked Os complexes.