Robust Polyaromatic Octasilsesquioxanes from Polybromophenylsilsesquioxanes, BrxOPS, via Suzuki Coupling

Polybromophenylsilsesquioxane (Br x OPS), 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 Br 5.3 OPS 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 °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 π−π* 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.