Theoretical insights into the host-guest interactions between [6] cycloparaphenyleneacetylene and its anthracene-containing derivative and fullerene C₇₀

The host-guest complexes formed with [6]cycloparaphenyleneacetylene ([6]CPPA) and its anthracene-containing derivative ([6]CPPAs) hosts and fullerene C₇₀ guest were explored by density functional calculations. Besides two previously reported configurations in which C₇₀ guest is standing or lying in the cavity of the host, we found a new kind of configuration in which C₇₀ guest is half-lying in the cavity of the host. More interestingly, the calculated results revealed that the fine-tuning deformations occur readily during the formations of the complexes, suggesting that both [6]CPPA and [6]CPPAs are highly elastic host molecules. The large host -guest binding energies indicate that both two host molecules, [6]CPPA and [6]CPPAs, have excellent encapsulation ability for C₇₀ guest, and the [6]CPPAs even has much better encapsulation ability for C₇₀ than [6]CPPA. Furthermore, the host-guest interactions regions were detected and visualized in real space based on the electron density and reduced density gradient. Additionally, ¹H NMR spectra of those three different kinds of configurations mentioned earlier have been calculated with gage-independent atomic orbital method, which may be helpful for further experimental characterizations in future.