Robust polyaromatic octasilsesquioxanes from polybromophenylsilsesquioxanes, BrxOPS, via Suzuki coupling

Polybromophenylsilsesquioxane (BrxOPS), where x = 5.3 (p:m = 65:25), because of its octahedral structure and nanometer size, represents a potentially very useful nanoconstruction site. We report here that Br5.3OPS reacts readily with borates of phenyl, biphenyl, naphthyl, 9,9-dimethylfluorene, and thiophene using standard Suzuki conditions to produce the corresponding polyaromatic and heteroaromatics with complete substitution of all bromines. The resulting materials, because of the 3-D octahedral structure, are completely soluble in a variety of common organic solvents. They are also stable to temperatures exceeding 400 degrees C in air, making them quite robust and easily processable. UV-vis spectra of these materials are red-shifted 20-30 nm from the simple organics, suggesting some conjugation with the silica cage core. Photoluminescence measurements show standard aromatic pi-pi* behavior with typical quantum efficiencies except for the 9,9-dimethylfluorene compound, which has an unexpectedly high quantum efficiency > 95%. The resulting compounds offer potential for further functionalization.