Toward a Reversible Isolation of a C20 Fullerene Inside a Tetraureacalixarene Dimer. A Theoretical Study
2006-08-03T00:00:00Z (GMT) by
The potential stabilization of normally unstable C20, the smallest fullerene, via its encapsulation inside a tetraureacalixarene dimer has been analyzed using molecular mechanics calculations with different force fields, the self-consistent-charge density-functional tight-binding with dispersion correction (SCC-DFTB-D) model, and standard density-functional-theory (DFT) calculations. The interaction energies obtained for the C20 complex have been compared with analogous values calculated for numerous complexes of the tetraureacalixarene dimer with other guests. Results of the calculations with all force fields and SCC-DFTB-D predict that the binding of C20 occurs with the highest selectivity. On the other hand, standard DFT calculations fail to correctly describe the stabilization of the complexes under study as standard DFT generally does not treat dispersion interactions properly. Predicted relative stabilities of the complexes are discussed in conjunction with available experimental data. Molecular dynamics simulations reveal the instability of the guest-free capsular dimer, which decomposes on a 1-ns time scale, while dimeric complexes with guests remained intact during the 5-ns simulation time, indicating the guest-driven formation of the molecular capsule.