From the analysis of the polarizability of carbon nano-onions (CNOs), it was concluded that CNOs behave as near perfect nanoscopic Faraday cages. If CNOs behave as ideal Faraday cages, the reactivity of the C240 cage should be the same in Li+ @C240 and Li+ @C60 @C240 . In this work, the Diels-Alder reaction of cyclopentadiene to the free C240 cage and the C60 @C240 CNO together with their Li+ -doped counterparts were analyzed using DFT. It was found that in all cases the preferred cycloaddition is on bond [6,6] of type B of C240 . Encapsulation of Li+ results in lower enthalpy barriers due to the decrease of the energy of the LUMO orbital of the C240 cage. When the Li+ is placed inside the CNO C60 @C240 , the decrease in enthalpy barrier is similar to that of Li+ @C240 . However, the location of Li+ in Li+ @C240 (off-centered) and Li+ @C60 @C240 (centered) is quite different. When Li+ was placed in the center of the C240 cage in Li+ @C240 , the barriers increased significantly. Taking into account this effect, the barriers in Li+ @C240 and Li+ @C60 @C240 differ by about 4 kcal mol-1 . This result can be attributed to the shielding effect of C60 in Li+ @C60 @C240 . As a result, we conclude that this CNO does not act as a perfect Faraday cage.
Keywords: Diels-Alder; Faraday cages; buckyonions; carbon nano-onions; fullerenes.
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