Poly(bromooctaphenylsilsesquioxane)s (Br
x
OPS) 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. Br
x
OPS 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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.