Host-Guest Chemistry and Reactivity

Encapsulation of Reactive Species


Ordinarily-pyrophoric white phosphorus (P₄) could be isolated as an air-stable complex through encapsulation by a water soluble tetrahedral Fe₄L₆ cage,[1] providing striking example of the ability of metal-organic capsules to modulate guest reactivity. The same cage is also capable of selectively binding and sequestering the potent greenhouse gas SF₆ from a mixture of gases, preventing the climatic impact of releasing it into the atmosphere,[2] and has been used as a whole molecule ‘supramolecular protecting group’.[3]

Selective guest binding and sensing


Some of our cages can selectively bind guests thanks to a good match between cavity and guest shapes as well as complementary interactions. A variety of guest types can be bound such as natural products[1,2] or anions,[3,4] among others.[5] Cages can be designed to serve as sensor for the desired guests by incorporating, for example, fluorescent moieties.[1


Complex host-guest assemblies

In addition to binding a single guest we have used metal-organic capsules to bind multiple guests or guests that can also act as hosts. A large tetrahedral capsule constructed from metalloporphyrin-based subcomponents was able to form host-guest complexes containing up to four fullerenes allowing the electronic properties of these unique fullerene clusters to be tuned through encapsulation.[1] Another tetrahedron was able to encapsulate a covalent cage, cryptophane-111 (CRY) which was in turn capable of accommodating a cesium cation or xenon atom, with altered kinetics and thermodynamics compared to the CRY host alone.[2] Enantiopure CRY could be bound with high enantioselectivity and stereochemical information was transfered from the inner covalent cage to the outer self-assembled capsule, leading to the formation of enantiopure Russian Doll complexes.

New nanoscopic environments


Self-assembled cages can be constructed with a variety of panels that will create a new environment – a nanospace – for encapsulated guests. This new nanoscale environment can be used to probe the response of guests in conditions normally inaccessible on a macroscopic scale.[1,2]