Subcomponent Self-Assembly and Guest-Binding Properties of Face-Capped Fe4L4 8+ Capsules

A general method for preparing Fe4L4 face-capped tetrahedral cages through subcomponent self-assembly was developed and has been demonstrated using four different C 3-symmetric triamines, 2-formylpyridine, and iron(II). Three of the triamines were shown also to form Fe2L3 helicates when the appropriate stoichiometry of subcomponents was used. Two of the cages were observed to have nearly identical Fe–Fe distances in the solid state, which enabled their ligands to be coincorporated into a collection of mixed cages. Only one of the cages combined a sufficiently large cavity with the sufficiently small pores required for guest binding, taking up a wide variety of guest species in size- and shape-selective fashion.