Selective N_sp2‐ and C_sp2‐ Photografting of Au‐Surface by Aryldiazonium Salts and Arylazo Sulfonates

Abstract

Arylazo sulfonates (ArÀ N=NÀ SO 3 Na) have been found to undergo photografting on gold surface through both AuÀ N sp2 À and AuÀ C sp2 À 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 AuÀ 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 AuÀ Ar bonds) and a concerted reaction on the surface of gold (for AuÀ N=NÀ Ar bond formation). The occurrence of an aryl radical upon irradiation has been fully evidenced by EPR spectroscopy. Finally, E/Z photoisomerisation of the N=N bonds present on prepared few layer films has been observed by means of UV-Vis absorption spectroscopy.

Nanometrology based control: taming radical grafting reactions with attoliter precision

“…16–20 Moreover, aryl-radicals are relatively stable and thus able to diffuse for at least a few tens of nanometers before reacting, 21,22 often leading to resolution loss and decreasing the fabrication precision. The benefits of developing controlled aryl-radical addition is however high, motivating considerable efforts towards methodologies for their generation 23,24 and surface addition control. 22,25–29 Indeed, several precursors have emerged for triggering aryl radicals formation, such as aryl halides, aryltriflates, 8 aryl iodonium salts, 30 arylazosulfonates, 24 etc .…”

“…The benefits of developing controlled aryl-radical addition is however high, motivating considerable efforts towards methodologies for their generation 23,24 and surface addition control. 22,25–29 Indeed, several precursors have emerged for triggering aryl radicals formation, such as aryl halides, aryltriflates, 8 aryl iodonium salts, 30 arylazosulfonates, 24 etc .…”

Visible photons as ideal reagents for the activation of coloured organic compounds

“…Arylazo sulfones (Scheme 1f) 35,36 and arylazo sulfonates 68 show an absorption band in the 400–450 nm range, arising from a nπ* transition. Irradiating these sulfones with blue light induces the homolytic cleavage of the N–S bond, resulting in the subsequent formation of aryldiazenyl, sulfonyl and aryl radicals, 35 making these compounds ideal candidates for the uncatalyzed formation of C–C bonds.…”