Extending supramolecular fullerene-porphyrin chemistry to pillared metal-organic frameworks

Abstract

Porphyrins and fullerenes are spontaneously attracted to each other. This supramolecular recognition element can be exploited to produce ordered arrays of interleaved porphyrins and fullerenes. C60·H2TpyP· Pb(NO3)2·1.5TCE (H2TpyP = tetra-4-pyridylporphyrin; TCE = 1,1,2,2-tetrachloroethane) crystallizes in the tetragonal P4/n space group and the structure has been solved to high resolution. The Pb2+ ions connect the pyridylporphyrins in infinite sheets with an interlayer spacing of 12.1 Å. The fullerenes are intercalated between these layers, acting as pillars. The 6:6 ring juncture bonds of C60 are centered over the porphyrins, bringing the layers into strict tetragonal register. This arranagement identifies the fullerene-porphyrin interaction as a structure-defining element. The same motif is seen in a related ribbon structure having C70 intercalated into Hgl2-linked H2TpyTP. The supramolecular design principles involved in assembling these chromophores may have applications in materials science.