Inclusion complexes of buckycatcher with C60 and C70

The dispersion corrected B97-D functional studies find a previously overlooked conformer of the buckycatcher C60H28 (2) exhibiting intramolecular pi-pi stacking of its corannulene pincers to represent a global potential energy minimum conformation. B97-D/TZVP calculated geometry of C-60@2 supramolecular assembly is in excellent agreement with the X-ray structure, slightly better than the previously reported M06-L results. In contrast, our calculated binding energy of C-60@2 complex is dramatically higher than both M05-2X and M06-2X results and we conclude that the latter numbers are grossly underestimated. The lack of specificity of the buckycatcher for molecular recognition of C-60 vs. C-70 fullerenes is predicted by our calculations and confirmed by the NMR titration experiment which provides the equilibrium constant of 6800 +/- 400 M-1 for association of C-70 with C60H28 which is only slightly lower than the previously reported association constant of C-60@2 assembly.