Abstract
Four porphyrins equipped with imidazolium rings on the para positions of their meso aryl groups were prepared and used as tetrakis(N-heterocyclic carbene) (NHC) precursors for the synthesis of porphyrin cages assembled from eight NHC-M bonds (M = Ag+ or Au+). The conformation of the obtained porphyrin cages in solution and their encapsulation properties strongly depend on the structure of the spacer -(CH2)n- (n = 0 or 1) between meso aryl groups and peripheral NHC ligands. In absence of methylene groups (n = 0), porphyrin cages are rather rigid and the short porphyrin-porphyrin distance prevents encapsulation of guest molecules like 1,4-diazabicyclo[2.2.2]octane (DABCO). By contrast, the presence of methylene functions (n = 1) between meso aryl groups and peripheral NHCs offers additional flexibility to the system allowing the inner space between the two porphyrins to expand enough to encapsulate guest molecules like water molecules or DABCO. The peripheral NHC-wingtip groups also play a significant role on the encapsulation properties of the porphyrin cages.