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-C equivalent to C)(3)Sn(CH2)(2)(CF2)(7)CF3, 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)(7)CF3, 2. The modified powders have been thoroughly characterized using elemental analysis, FTIR spectroscopy, solid-state Si-29, C-13, and Si-29 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 degrees 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.