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

Abstract

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. The surface coverage of the azobonded 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 benzene-linked Os complexes.4COOH)] 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. The surface coverage of the azobonded 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 benzene-linked Os complexes.=N bonds tethering the complexes to Au. The surface coverage of the azobonded 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 benzene-linked Os complexes.