Supramolecular Structures of Inclusion Complexes of C70 and Cyclic Porphyrin Dimers

Cyclic nickel and free-base porphyrin dimers (Ni2-CPDPy and H4-CPDPy) include fullerene C70 both in solution and in the crystals. Based on the 13C NMR spectra in solution, the included C70 molecule inside the cavity of Ni2-CPDPy shows both end-on and side-on orientations, whereas the C70 molecule within H4-CPDPy has only a side-on orientation toward the porphyrin rings. X-ray crystallography revealed both “end-on” and “side-on” orientations of C70 in the crystal structure of the inclusion complex of Ni2-CPDPy and C70. This is the first example of an X-ray crystallographic determination for an end-on orientation of C70 cocrystallized with porphyrins. On the other hand, only a side-on orientation of C70 was observed in the crystal structure of the complex of H4-CPDPy and C70. Further, a zigzag array of C70 molecules through van der Waals contacts with each other is formed along the monoclinic b axis in the latter crystal.