Composition-selective full inclusion host-guest interaction of azobenzene-containing photoresponsive nanoring with fullerene C60

By means of density functional theory calculations, the encapsulation capabilities of a series of azobenzen-containing photoresponsive nanoring hosts (labeled as host 1, 2, 3, 4, 5 and 6 according to the number of the azo unit, respectively) for fullerene C-60 were surveyed. Interestingly and abnormally, it is found that the host 5, of which the diameter is only 1.218 nm, can form stable full inclusion complex with C-60. However, irrespective of their cavity sizes (11.98 similar to 12.94 angstrom) of the hosts, the structures 1 similar to 4 and 6 were all disable to form inclusion complex with C-60. In this paper, the group-number-composition-selective full inclusion host-guest interaction of the azobenzene-containing nanorings with fullerene C-60 is firstly presented. The calculated interaction energies, together with the detection and visualization of the weak interaction regions, provided evidences for the host-guest binding based on relative strong repulsion interaction in the full inclusion complex. Analysis on the frontier orbital feature of the host-guest systems suggests that under the electron excited condition, the chemical activity may be transferred from host 5 to guest C-60 by formation of the floating host-guest complex, and the chemical reactivity of the host 5 can be passivated via formation of the full inclusion host-guest complex. Additionally, UV-vis-MR and H-1 NMR spectra of the hosts before and after the formations of the complexes have been simulated and discussed qualitatively, which may be helpful for further experimental investigations in future.