Systems Chemistry and Chemistry Between Phases
Post-assembly modification of discrete supramolecular complexes has received increasing attention in recent years. Our group has utilised this strategy to address numerous objectives: modular functionalisation of self-assembled structures,[1,2,3] preparing new functional covalent architectures that are difficult to synthesise using conventional organic methods,[4,5,6] and using post-assembly modification to trigger phase transfer and separation of cages and cargoes.[7,8]
Fuelled Cage Assembly
An approach in which triphenylphosphine is used as a chemical fuel to maintain CuI-based self-assembled metallosupra-molecular architectures for defined periods of time was developed. This method was used to exert control over the threading and dethreading of the ring of a pseudorotaxane’s axle, as well as to direct the uptake and release of a guest from a metal-organic host. Management of the amount of fuel and catalyst added allowed for time-dependent regulation of product concentration.
Transport of molecules between several spatial locations is essential in the context of chemical separations and complex natural systems. We were able to achieve controlled directional transport of cages and their cargoes across phase boundaries, allowing for the design of a triphasic sorting system in which three coordination cages with their respective cargoes each segregated into a distinct ionic liquid layer. We also demonstrated circular transport of a cage between three solvent phases, where the direction of transfer was controlled by the order of application of distinct chemical signals. Selective extraction of a high-value anion perrhenate from water to organic solvent was recently accomplished by using a Fe₄L₄ cage.
Electron-rich anilines were able to displace electron-deficient anilines of a BODIPYs-containing cage which has tuneable photosensitizing properties. When iodoaniline residues were incorporated, heavy-atom effects led to enhanced singlet oxygen production. The incorporation of (methylthio)aniline residues into a cage allowed for the design of an autocatalytic system: oxidation of the methylthio groups into sulfoxides make them electron-deficient and allows their displacement by iodoanilines, generating a better photocatalyst and accelerating the reaction.