Controlling the Confinement and Alignment of Fullerene C₇₀ in para-Substituted Calix[5]arenes

Graphical Abstract

Complexes of fullerene C₇₀ with p-benzylcalix[5]arene and p-phenylcalix[5]arene were structurally authenticated. The fullerene molecules are completely shrouded by two calix[5]arenes in a capsular arrangement (see figure). The Hirshfeld surfaces of two complexes have been investigated for a detailed understanding of the orientation and nature of interactions of C₇₀ with the cavitand-type molecules.

Abstract

In toluene fullerene C₇₀ forms 2:1 complexes with p-benzylcalix[5]arene (1) and p-phenylcalix[5]arene (2), [C₇₀⊂1₂]⋅6 (C₇H₈) and [C₇₀⊂2₂]⋅7 (C₇H₈). The fullerene molecules are completely shrouded by two calix[5]arenes in addition to terminal benzyl groups from other supermolecules, [C₇₀⊂1₂], and solvent. Within the capsule-like supermolecules the calixarenes have distinctly different arrangements relative to the principal axis of the fullerene; for [C₇₀⊂1₂]⋅6 (C₇H₈) the oxygen planes of the two calixarenes are skewed by 37.0 and 47.5°, whereas in [C₇₀⊂2₂]⋅7 (C₇H₈) the principal axes of the fullerene and the two encapsulating calixarenes are more closely aligned with the corresponding angles at 9.7 and 8.6°, and features a pentaphenyl inter-calixarene embrace. The Hirshfeld surfaces of these two complexes have been investigated for a detailed understanding of the orientation and nature of interactions of C₇₀ with the cavitand-type molecules and toluene.