Chiral Branched Inorganic−Organic Nanocages

We demonstrated how ionic pairing of sulfonated polyhedral oligomeric silsesquioxane (POSS-SO3H) nanocages with protonated amino acid, l-tryptophan, can yield chiroptically active hybrid inorganic−organic nanostructures. We discovered that preferential complementary Coulombic interactions at the silsesquioxane nanocage vertices drive molecular organization into chain-like supramolecular assemblies of modified nanocage clusters with distinctive nanofibrillar and globular morphologies. The resulting POSS-SO3−−TRP+ hybrid exhibits pH-resilient chiroptical activity, improved electrokinetic activity in comparison to free l-tryptophan, and a higher glass transition temperature upon ionic complexation. These results suggest that ionic inorganic nanocages act as a viable scaffold for stabilizing molecular chirality under mild aqueous conditions, opening a facile route to optically active organic−inorganic assembled chains with tunable robust chiroptical properties of inorganic nanostructures.