All the pseudopolymorphs P6-I -P6-IV are highly solvated. In P6-II, P6-III and P6-IV, the solvent-accessible voids (probe radius 1.2 Å, calculated with Mercury 4.0 software 19 after removing the refined solvent molecules) constitute between 28% to 33% of the unit cell volume (Fig. ). On the other hand, the herringbone-type packing in P6-I reduces the void volume by more than a factor of two (13%, see Fig. ), reflecting impact of the packing on the porosity. Structure P6-C60. All the structures discussed above are for the zinc nanoring c-P6 coordinated to the T6 template. The presence of the bound template, and coordination to metal cations, increases the rigidity of this nanoring complex. Now we turn to the free-base nanoring with no template, which is expected to be more flexible. Porphyrins were extensively used by Balch, Olmstead, and coworkers as co-crystallization partners to obtain crystal structures of functionalized fullerenes. We decided to use a reverse strategy to facilitate crystallization of porphyrin nanorings, taking inspiration from the many reported fullerene-porphyrin nanostructures. We hypothesized that π-stacking of fullerene molecules to the porphyrinic walls could govern their assembly into 2D sheets.