Synthesis of functionalized silica nanostructure: Unexpected conversion of cyanopropyl group in chloropropyl one during HCl-catalysed hydrolysis of the corresponding triethoxysilane

• 3-cyanopropyltriethoxysilane was subjected to hydrolysis in the presence of HCl 37%.
• Gradual change of nitrile groups in hydrolysis conditions were monitored spectral.
• Substitution of the nitrile group with chlorine occurred during acid hydrolysis.
• [Cl(CH3)3]8Si8O12 exhibiting negligible elongation in inner cage was formed.
• Thermal and moisture behavior and biological activity were evaluated.

During acid hydrolysis of 3-cyanopropyltriethoxysilane (CyTES) in a molar ratio HCl:CyTES – 4.6:1 in methanol, with the intention to prepare the properly polyhedral oligomeric silsesquioxane (POSSQ) or carboxyl derivative, the conversion of organic functional group occurred by replacing the CN group with Cl forming octakis(chloropropyl)octasilsesquioxane (Cl-POSSQ). The structure was determined through X-ray single crystal diffraction, spectral (FTIR and NMR) techniques and elemental analysis. The stepwise conversion of the CN group during the 3-cyanopropyltriethoxysilane hydrolysis was monitored through IR and 13C NMR spectroscopy. Thermal behavior was studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Moisture sorption capacity was evaluated by water vapor sorption in dynamic regime (DVS). The biological activity was in vitro tested against three fungi and two bacteria.

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