Spherical, Polyfunctional Molecules Using Polybromooctaphenylsilsesquioxanes as Nanoconstruction Sites

Richard Laine

R. TSKMAMRTNRL C. M. Brick (2005)

Macromol., 38:4655-60.

Poly(bromooctaphenylsilsesquioxane)s (BrxOPS) are easily synthesized from octaphenylsilsesquioxane (OPS) via bromination with Br2/Fe in dichloromethane. For Br:OPS ratios less than 8:1, singly brominated products are obtained with 65−70% para substitution, 25−20% meta substitution and the remainder ortho. Higher ratios provide dibrominated products up to Br16OPS. Surprisingly, the disubstitution pattern is completely different with 80% 2,5 substitution (meta and ortho to Si), indicating extensive rearrangement with addition of the second bromine. BrxOPS bromo functionality is readily transformed via low temperature catalytic coupling reactions with para-substituted styrenes, tetraphenylborate, methyl methacrylate, or toluidine into the corresponding fully substituted p-stilbenes, p-biphenyls, methyl cinnamates, and diarylamines. The p-stilbenes offer unusually large red shifts and order of magnitude increases on photoluminescence quantum efficiencies over stilbene itself. Methyl methacrylate addition provides a mechanism for forming cross-linkable films and can be used in conjunction with the other functionalization reactions. Reactions with phenylacetylenes occur with concomitant formation of vinyl bromides, which appear to react further, adding second acetylene groups. The fact that each phenyl group occupies a different octant in Cartesian space, for Br≤8OPS primarily para, offers the opportunity to create novel eight branched, highly conjugated cores of value in their own right but also of value as three-dimensional, eight or 16 branched, aromatic cores for the synthesis of dendrimer-like and/or hyperbranched molecules.

nanobuilding blocks, silsesquioxanes