Synthesis improvement and characterization of polyhedral oligomeric octa (aminophenyl) silsesquioxane

On the 5% Pd/C-FeCl₃ catalyst, octa (aminophenyl) silsesquioxane (OAPS) was prepared in tetrahydrofuran (THF) using hydrazine hydrate as reductant from octa (nitrophenyl) silsesquioxane (ONPS) in 1 h. Compared with the synthesis methods in the references, this synthetic process was simple and stable, with shortened reaction period, increased yield and promoted catalytic efficiency. The product was characterized by FTIR, ¹H NMR and gel permeation chromatography (GPC) and it was found that nitro groups were completely converted to amino groups. An intermediate with N, N-dihydroxyaminophenyl groups and hydroxylaminophenyl groups was obtained when the only 5% Pd/C was used as catalyst. The synthesis mechanism of OAPS from ONPS was studied based on the intermediate compound. In nitro groups reduction, N, N-dihydroxyaminophenyl groups were firstly formed through two-electron transfer, then hydroxylaminophenyl groups were generated through dehydration/hydrogenation and finally aminophenyl groups were produced after further reduction. At the beginning, hydrazine hydrate was mainly oxidated to N₂ and H₂, but its oxidative products changed to N₂ and NH₃ when all of the ONPS were completely converted to OAPS.