Selective Nsp2‐ and Csp2‐ Photografting of Au‐Surface by Aryldiazonium Salts and Arylazo Sulfonates

Abstract

AbstractArylazo sulfonates (Ar−N=N−SO3Na) have been found to undergo photografting on gold surface through both Au−Nsp2− and Au−Csp2− bond formation. The functionalized materials have been fully characterized by infrared reflection absorption spectroscopy (IRRAS), Raman, XPS, DFT calculations and UV‐Vis absorption spectroscopy. These methods permit to evidence aromatic substituents (IRRAS), the Au−N=N signature (Raman and XPS spectroscopy), and the bond dissociation energy values of the two linkages (DFT calculation). The grafting proceeds through two competitive paths, namely a stepwise reaction involving an aryl radical (for the formation of the Au−Ar bonds) and a concerted reaction on the surface of gold (for Au−N=N−Ar bond formation). The occurrence of an aryl radical upon irradiation has been fully evidenced by EPR spectroscopy. Finally,E/Zphotoisomerisation of the N=N bonds present on prepared few layer films has been observed by means of UV‐Vis absorption spectroscopy.