A protecting-deprotecting strategy for structuring robust functional films using aryldiazonium electroreduction

The influences of the size, position, nature of different silyl protecting groups on resulting covalently bound films obtained by electroreduction of ethynyl-aryldiazonium salts were investigated in view of preparing robust and functional interfaces with well-controlled structure and properties. Three different protecting groups where the active function was introduced on one meta position of the aryl ring were considered: trimethylsilyl (TMS), triethylsilyl (TES) and tri(isopropyl)silyl (TIPS). As a general tendency, ultra thin and robust active functional layers were obtained on carbon substrates after deprotection (loss of the silyl group) by treatment with nBu4BF4. Multilayer formation occurs when the protective group is just a TMS but becomes negligible when TIPS is used. Interestingly, the structure of the final layer keeps a memory of the silyl group used during the electrografting that permits a tweaking of the blocking properties and of the layer thicknesses. As a remarkable feature, all layers present large density of active alcyne terminations that remain totally available for further “click chemistry” coupling. These possibilities were tested with a redox label (azidomethylferrocene).