Synthesis of Diazonium Tetrachloroaurate(III) Precursors for Surface Grafting

Abstract

The synthesis of diazonium tetrachloroaurate(III) complexes [R-4-C6H4N≡N]AuCl4 involves protonation of anilines CN-4-C6H4NH2, C8F17-4-C6H4NH2, and C6H13-4-C6H4NH2 with tetrachloroauric acid H[AuCl4] 3H2O in acetonitrile followed by one-electron oxidation using [NO]PF6. FT-IR shows the diazonium stretching frequency at 2277 cm−1 (CN), 2305 cm−1 (C8F17), and 2253 cm−1 (C6H13). Thermogravimetric Analysis (TGA) shows the high stabilities of the electron-withdrawing substituents C8F17 and CN compared with the electron-donating substituent C6H13. Residual Gas Analysis (RGA) shows the release of molecular nitrogen as the main gas residue among other small molecular weight chlorinated hydrocarbons and chlorobenzene. Temperature-Dependent X-Ray Powder Diffraction (TD-XRD) shows the thermal decomposition in C6H13 diffraction patterns at low temperature of 80 °C which supports the TGA and RGA (TGA-MS) conclusions. X-ray structure shows N≡N bond distance of approximately 1.10 Å and N≡N-C bond angle of 178°.

Keywords

• diazonium
• tetrachloroaurate(III)
• X-ray