Self-Assembled Tin-Based Hybrid Materials

Hydrolysis-condensation of organically bridged o , )-bis(trialkynyltin) compounds 2 was the second route investigated to prepare class II tin-based hybrid materials. At first, hydrolysis conditions of 2 were determined to get transparent gels. As gelling of neutral solutions is very slow, acidic or basic conditions were employed to accelerate the process. Whatever the compound 2 and the water amounts used, base-catalyzed 

Tilt angle Determined from X-ray line broadening ( 0.5 nm) Calculated postulating a fully extended linker Calculated assuming a doubly folded linker 

Hydrolyses have also been conducted in micro-emulsions, using non-ionic surfactants. In this case, self-assembled tin-based hydrid materials are prepared, regardless of the nature of the precursor molecule (Table 3.2.4). Micro-emulsion conditions are therefore required to organize the hybrid containing the flexible alkylene spacers. 

The textural properties of the hybrid materials are also strongly dependent upon the hydrolysis conditions and the nature of the linker. After hydrolysis in a homogeneous medium, nitrogen adsorption and TEM measurements indicate the formation of non-porous solids with BET specific surface areas lower than 7 m except for 2g. Variation of the precursor concentration does not strongly affect these values. In contrast, hydrolysis under microemulsion conditions leads to a significant increase in the specific surface areas, mainly in the case of the flexible alkylene linker (Table 3.2.5). 

Compounds 2a and 2d, which contain arylene and 4,4 -dimethylenebiphenyl, respectively, behave similarly, but the main difference lies in the size of the particle formed after 24 hours, which is much smaller than that measured for 2f. Furthermore, the hydrolysis rate of the latter is much lower, as evidenced 

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The synthesis and the structure of self-assembled tin-based hybrid materials prepared from 2 (Scheme 3.2.2) are then reported, as well as the textural and structural properties of the tin dioxide materials obtained after annealing these hybrids. 

Scheme 3.2.2 Chemical formulae of organically bridged a,co-bis(trialkynyltin) compounds 2 used for the preparation of self-assembled tin-based hybrid materials...

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