Inclusion complexes of buckycatcher with C60 and C70

Abstract

The dispersion corrected B97-D functional studies find a previously overlooked conformer of the buckycatcher C₆₀H₂₈ (2) exhibiting intramolecular π–π stacking of its corannulene pincers to represent a global potential energy minimum conformation. B97-D/TZVP calculated geometry of C₆₀@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 C₆₀@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 C₆₀vs. C₇₀ 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 C₇₀ with C₆₀H₂₈ which is only slightly lower than the previously reported association constant of C₆₀@2 assembly.