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

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. C(60) x H(2)TpyP x Pb(NO(3))(2) x 1.5TCE (H(2)TpyP = 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 Pb(2+) ions connect the pyridylporphyrins in infinite sheets with an interlayer spacing of 12.1 A. The fullerenes are intercalated between these layers, acting as pillars. The 6:6 ring juncture bonds of C(60) are centered over the porphyrins, bringing the layers into strict tetragonal register. This arrangement identifies the fullerene-porphyrin interaction as a structure-defining element. The same motif is seen in a related ribbon structure having C(70) intercalated into HgI(2)-linked H(2)TpyTP. The supramolecular design principles involved in assembling these chromophores may have applications in materials science.