Optical Rotatory Silica Materials Prepared via Sol−Gel Processes

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A series of transparent, monolithic silica materials doped with 5−20 wt % of (−)-dibenzoyl-l-tartaric acid (DBTA) and (+)-d-glucose have been prepared via the acid-catalyzed sol−gel reactions of tetraethyl orthosilicate in the presence of the organic dopants. The materials show optical rotations, which can be directly measured on a common polarimeter. The optical rotation was found to be proportional to the dopant concentration and to the thickness of the samples. The specific rotations measured at 589 nm at 25 °C are +53° for the d-glucose-doped and −112° for the DBTA-doped silica samples, which are close to those for the same compounds measured in liquid solutions. Both the DBTA- and d-glucose-doped silicas exhibit a simple normal dispersion with negligible concentration effects. The organic compounds retain their stereochemical structures during the sol−gel reactions and, therefore, their optical activities. These materials can be regarded as nanocomposites in which the organic dopants uniformly distribute in the amorphous silica networks.