Formation of trimethylsilylated open-cage oligomeric azidophenylsilsesquioxanes

Formation of open-cage oligomeric azidophenylsilsesquioxane was surprisingly discovered in the successive reduction and azidation reactions starting from octa(nitrophenyl)octasilsesquioxane. The mixture of oligomeric products was characterized after end-capping with trimethylsilyl groups. The IR spectra confirmed the introduction of azide function to aromatic moiety, and trimethylsilyl group on silsesquioxane framework. Together with the GPC result, NMR analysis revealed the introduction of different number of trimethylsilyl groups in the structure. Some of them maintained the cage-like silsesquioxane structure characterized by XRD analysis. Their TGA profiles gave a unique pattern with clear two-step mass loss with the first mass loss of about 8–10 wt% from 180 to 225 °C corresponding to a thermal decomposition of azide groups.

The formation of oligomeric azido-functionalized phenylsilsesquioxane with ring-opened structure was surprisingly discovered by using tert-butyl nitrite and azidotrimethylsilane on octa(aminophenyl)octasilsesquioxane.Figure optionsDownload as PowerPoint slideHighlights
► Azidation reaction on octa(aminophenyl)octasilsesquioxane by t-BuONO and TMSN3 results in the organo-transformation from amino to azide groups.
► The products with a number of end-capping trimethylsilyl groups in silsesquioxane framework have been isolated.
► The latter action is due to a catalytic ring-opening of inorganic Si-O-Si cores on silsesquioxane framework by the trace of water and nucleophilic azide.