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 Sibulk-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