Less is More: A Shortcut for Anionocages Design Based on (RPO3 2- )-Monourea Coordination.

Anionocages have been developed as a unique family of hydrogen bonded cages. However, strategies for constructing anionocages are mainly limited to that based on (PO4 3- )-bisurea coordination, neither the ligands nor the anions lack the simplicity and diversity of the maturely developed analogues based on metal coordination (i.e. metallocage). We report herein a more simple strategy for anionocages design based on (RPO3 2- )-monourea coordination, utilizing monourea rather than bisurea as the hydrogen binding donor, and RPO3 2- rather than PO4 3- as the acceptor. Two fluorescent, quadruple helicate anionocages were constructed by a bis-monourea ligand, and dianions PhOPO3 2- (H1 ) or HOPO3 2- (H1A ), respectively, which were capable of encapsulating a series of cation guests. As revealed by molecular modeling, H1 features remarkable guest-adaptive cavity breathing without change of the quadruple helicate topology, which allowed the encapsulation of different sized guests in an "induced fit" manner.