Single-crystal X-ray diffraction

A summary of the crystallographic data and structural refinements for 1, 1a and C₆₀@1a and anthracene@1a are given in Supplementary Table ¹. All crystallographic data were collected at 173 K on a Bruker D8–Venture diffractometer with graphite–monochromated Mo Kα radiation (λ = 0.71073 Å) (1a) and Cu Kα radiation (λ = 1.5418 Å) (1, C₆₀@1a and anthracene@1a). The data were collected using the program APEX 3 and processed using the program SAINT routine in APEX 3. The structures were solved by direct methods with SHELXS–2014 and refined with SHELXL–2014 program^42,43. All non–hydrogen atoms, except disordered C₆₀ and anthracene, were refined in anisotropic approximation. Hydrogen atoms were refined in geometrically calculated positions using the “riding model” with U_iso(H) = 1.2U_iso(C). The large cell volume and high crystal symmetry did not allow refining the disordered solvent molecules and dimethylamine counter cations within the crystal lattices, therefore, SQUEEZE routines in PLATON were used for 1, 1a, and C₆₀@1a to generate the reflection intensities with subtracted solvent contributions⁴⁴. For 1, the sulfate groups were disordered, so the restraints DFIX and SADI were used to confine the bond length of sulfate groups. SIMU and ISOR constraints were used for organic ligands and partial metal centers with large thermal motions. For C₆₀@1a, the C₆₀ molecule was disordered, so the restraints SADI, FLAT, SIMU, RIGU, ISOR were applied to model the geometry of C₆₀, the ISOR constraints were used for dimethylamine cation with large thermal motion. For anthracene@1a, the anthracene and dimethylamine molecule were disordered, so the restraints SADI, FLAT, RIGU, and SIMU were used to confine the geometry of anthracene molecule, DFIX, ISOR, and SIMU constraints were used for dimethylamine cation with large thermal motion.