© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Molecular binding of fullerenes, C60 and C70, with the ZnII complex of a monomeric ring-fused porphyrin derivative (2-py) as a host molecule, which has a concave π-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 C60 molecule, the C60 molecule formed a π-π stacked pair with a C60 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 1 NMR spectral changes and the redox properties of 2-py upon the molecular binding. Play ball: Molecular binding of fullerenes, C60 and C70, with a monomeric ZnII complex of ring-fused porphyrin derivative (2-py), having a concave π-conjugated surface induced by the axial coordination (see figure), has been confirmed by spectroscopic measurements and X-ray diffraction analysis. The molecular sizes of the fullerenes significantly affect the 1H NMR spectral changes and the redox properties of 2-py upon molecular binding.