Light-induced Processes in Coordination Cages

Abstract

Metal/ligand coordination cages provide versatile opportunities for exploitation of useful photophysical properties in self-assembled systems. The metal ions or ligands can themselves be chromophoric and display useful photophysical properties, as in many simpler coordination complexes: but the hollow capsule-like nature of coordination cages means that the binding of guests inside the central cavities adds substantially to the possibilities for functional behaviour, as the guests may themselves be chromophoric or may interact with the array of excited-state chromophores in the cage that surrounds a bound guest. This chapter summarises the rapidly developing field of photoactive coordination cages and their applications in areas from size-/shape-specific sensing of substrates to photoinduced chemical transformations that occur inside the cage cavities.

Subphthalocyanine capsules: molecular reactors for photoredox transformations of fullerenes

“…3 The combination of the two fields, that is the formation of coordination cages by self-assembly of chromophores with photosensitizing abilities, offers powerful possibilities since it provides a local concentration of photoactive units surrounding a bound guest in a way that would not be possible in solution under normal conditions, affording an antenna effect in which excitation energy from several sources is directed to a single reaction site. Although there are examples in the literature of “antenna” cages performing as photocatalysts, 4,5 most of them are focused on the production of hydrogen or the generation of reactive oxygen species, and the realization of more complex photoredox transformations remains largely unexplored.…”

A chemiluminescent lantern: a coordination cage catalysed oxidation of luminol followed by chemiluminescence resonance energy-transfer

“… 2 If the components of the cage – the metal ions and bridging ligands – incorporate desirable photophysical or redox characteristics, then such cages can act as more than just molecular containers and can take an active role in photochemical reactions of bound guests. 3 Coordination cages are particularly appropriate for such studies as a large number of chromophoric and/or redox active component parts may be combined in a compact assembly in close proximity to a bound guest, which means that a guest may be surrounded by a local concentration of such reaction partners which would be impossible to attain under normal solution conditions. This is the basis of some recent examples of photo-redox catalysis using coordination cage hosts.…”