Synthesis and optical properties of rhodamine terminated organosilicon dendrimers

Abstract

Here we report on the synthesis of a series of branched organosilicon compounds bearing 2, 4, 6, 8, 12, 16 and 24 rhodamine 6G groups using the click conjugation strategy. Divinyldimethylsilane, tetravinylsilane, octavinylsilsesquioxane and vinyl terminated dendrimers on their basis were used as scaffolds to hold conjugated dye molecules. Obtained compounds were characterized by physical and photophysical methods and the change in the optical properties in the series was analyzed as a function of their functionalization. It was shown that absorption cross section of conjugated chromophores inversely depends on their local concentration (i.e. molecule functionalization), while the fluorescence intensity in the series is the same for all compounds starting from 4-functionalized and depends only on dendrimer concentration. On the basis of experimental data, theoretical calculations and literature, we hypothesized that PET and PHT mechanisms are responsible for fluorescence quenching.