Supramolecular Interaction of Fullerenes with a Curved pi-Surface of a Monomeric Quadruply Ring-Fused Porphyrin

Abstract

Molecular binding of fullerenes, C-60 and C-70, with the Zn-II complex of a monomeric ring-fused porphyrin derivative (2-py) as a host molecule, which has a concave pi-conjugated surface, has been confirmed spectroscopically. The structures of associated complexes composed of fullerenes and 2-py were explicitly established by X-ray diffraction analysis. The fullerenes in the 2:1 complexes, which consist of two 2-py molecules and one fullerene molecule, are fully covered by the concave surfaces of the two 2-py molecules in the crystal structure. In contrast, in the crystal structure of the 1:1 complex consisting of one 2-py molecule and one C-60 molecule, the C-60 molecule formed a pi-pi stacked pair with a C-60 molecule in the neighboring complex using a partial surface, which was uncovered by the 2-py molecule. Additionally, the molecular size of fullerene adopted significantly affects the H-1 NMR spectral changes and the redox properties of 2-py upon the molecular binding.