Guest-Induced "Breathing-Helical" Dynamic System of a Porphyrinic Metallo-Organic Cage for Advanced Conformational Manipulation.

Host-guest dynamic systems in coordination-driven metallo-organic cages have gained significant attentions since their promising applications in chiral separation, drug delivery, and catalytical fields. To maximize guest-binding affinity, hosts adopting multiple conformations are widely investigated on their structural flexibility for guest accommodation. In this study, a novel metallo-organic cage S with breathing inner cavity and freely twisted side chains was proposed. Single-crystal X-ray diffraction analyses depicted a characteristic "breathing-helical" dynamic system on the semiflexible framework, which led to an unprecedent co-crystallisation of racemic and symmetric conformations via the encapsulation locking of C guests. By taking advantages of the high binding affinity, selective extraction of C was realized. This research provides new ideas for the modification on the helicities of metallo-organic cages, which could pave a new way for advanced conformational manipulation of supramolecular host systems.