Fullerene Inclusion Based on Horning-Crown Macrocycles

Horning-crown macrocycles, 1(R = (CH₂)₂) and 2(R = (CH₂)₃) form inclusion complexes with C₆₀ and C₇₀ fullerenes which have been structurally authenticated using X-ray diffraction data. Macrocycle 1 affords a C₆₀ complex as a toluene solvate with overall composition C₆₀(1)₂(tol)₂, 3, whereas the larger macrocycle, 2, affords complexes with both C₆₀ and C₇₀ fullerenes, also as toluene solvates: C₆₀(2)(tol)₂, (4); C₇₀(2)(tol)₂, (5); and C₇₀(2)₂(tol)₂, (6). The higher degree of flexibility of such macrocyles relative to classical calixarenes is noteworthy in forming fullerene complexes, with the smaller ring size of 1 favoring fullerene complexation toward the smaller C₆₀ molecule. The supramolecular assemblies involve host−guest interactions as well as interaction of fullerenes in zigzag chains with interfullerene contacts close to the van der Waals limit.