Theoretical Prediction on a Novel Reduction-Responsive Nanoring Having a Disulfide Group for Facile Encapsulation and Release of Fullerenes C(60) and C(70)

[Image: see text] In this work, a novel reduction-responsive disulfide bond-containing cycloparaphenylene nanoring molecule (DSCPP) with a pyriform shape has been designed. In addition, the interactions between the designed nanoring (host) and fullerenes C(60) and C(70) (guests) were investigated theoretically at the M06-2X/6-31G(d,p) and M06-L/MIDI! levels of theory. By analyzing geometric characteristics and host–guest binding energies, it is revealed that the designed DSCPP is an ideal host molecule of guests C(60) and C(70). DSCPP presents excellent elastic deformation during the encapsulation of C(60) and C(70). The high binding energies suggest that both DSCPP⊃C(60) and DSCPP⊃C(70) (∼92 and 118 kJ·mol(–1) at the M06-2X/6-31G(d,p) level of theory) are stable host–guest complexes, and the guest C(70) is more strongly encapsulated than C(60) in the gas phase. The thermodynamic information indicates that the formation of the two host–guest complexes is thermodynamically spontaneous. In addition, the frontier molecular orbital (FMO) features and intermolecular weak interaction region between DSCPP and fullerenes gusts are discussed to further understand the structures and properties of the DSCPP⊃fullerene systems. Finally, the ring-opening mechanism of the DSCPP under reduction conditions is investigated.