A Self-Assembled Cage for Wide-Scope Chiral Recognition in Water.

Herein, we report the self-assembly of an anionic homochiral octahedral cage, by condensing six Ga 3+ cations and four trisacylhydrazone ligands. The robust nature of hydrazone bond renders the cage stability in water, where the cage can take advantage of hydrophobic effect for host-guest recognition. In addition to the internal binding site namely the inner cavity, the octahedral cage possesses four "windows", each of which represents an external binding station allowing peripheral complexation. These internal and external binding sites endow the cage with capability of binding a broad range of guests whose sizes could either be smaller than, or exceed the volume of the cage inner cavity. Upon accommodation of a chiral guest, one of the two cage enantiomers becomes more favored than the other, producing CD signals. The CD signal intensity of the cage is observed proportional to the ee values of the chiral guest, allowing quantitative determination of the latter.