Silsesquioxane Cage-Fused Siloxane Rings as a Novel Class of Inorganic-Based Host Molecules

Side-opened cage-silsesquioxane, denoted as SO-POSS, was fused with oligo(dimethylsiloxane)s to synthesize inorganic skeleton-based cyclic molecules. The resultant cyclic compounds served as hosts for alkali metal cations (Li+, Na+, K+). Interestingly, ring-transformation occurred in the presence of guest cations depending on the ring size; the SO-POSS-fused cyclic oligo(dimethylsiloxane)s were converted to smaller SO-POSS rings and cyclic oligo(dimethylsiloxane)s. Herein, we report the first study on host-guest chemistry of the cage silsesquioxane-fused siloxane rings. Cage-silsesquioxane was combined with oligo(dimethylsiloxane)s to construct cyclic compounds. The obtained cyclic siloxanes were examined as host molecules to reveal the association behavior with alkali metal cations. In addition, ring-transformation was observed in the presence of alkali metal cations.