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

A. M. RICCI; L. P. MENDEZ DE LEO; F. J. WILLIAMS; E. J. CALVO

Chemphyschem

WILEY-V C H VERLAG GMBH

Lugar: Weinheim; Año: 2012 vol. 13 p. 2119 - 2127

1439-4235

Molecular films obtained by electrochemical reduction of diaz- oniuim 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 X- ray photoelectron (XPS) and polarization-modulation infrared reflection absorption spectroscopy (PM-IRRAS). The spectro- scopic evidence suggests the formation of N=N bonds tether- ing the complexes to Au. 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 spectros- copy. Similar electron transfer-rate constants were measured for both fluorinated and non fluorinated benzene-linked Os complexes.