Functionalization of Silica Gel with Organotrialkynyltins:  New Method of Covalent Attachment of Organic Groups on Silica Gel

A new precursor molecule for chemical modification of oxide surfaces, the trialkynyl(fluoroorgano)tin(IV) (C₄H₉−CC)₃Sn(CH₂)₂(CF₂)₇CF₃, 1, was synthesized in three steps from tricyclohexyltin hydride. Compound 1 reacted with Biosepra 100 silica to give chain loadings as high as 0.28 mmol·g^-1 to be compared to 0.44 mmol·g^-1 reached with the trichlorosilane analogue Cl₃Si(CH₂)₂(CF₂)₇CF₃, 2. The modified powders have been thoroughly characterized using elemental analysis, FTIR spectroscopy, solid-state ²⁹Si, ¹³C, and ²⁹Si CP-MAS NMR, XPS, and TGA-MS. Irreversible chemisorption took place in solution at room temperature to give a fluorinated chain thin layer, likely a monolayer, via removal of three hex-1-yne molecules and formation of Si_bulk−O−Sn−C linkages. The chemisorption process involves hydrolysis of the precursor in solution before reaction with the silica surface and led to surface-modified silica thermally stable up to 350 °C. Trialkynylorganotins in solution might be therefore advantageously exploited to modify chemically SnO₂ or TiO₂ surfaces to get dye-sensitized oxide materials able to achieve light-to-electricity conversion.