Ab initio study of the aromaticity of hydrogenated [70] and [76]-fullerenes

An analysis is made of the global and local aromaticity for a series of hydrofullerenes of the type C70H2 and C76H2 at ab initio HF/3-21G level of theory, as well as their deprotonated analogues. Additions at the hexagonal bonds of the pyracylenic units are considered. The relation between this addition pattern and the magnetic properties is established, showing low aromatic regions to be preferred for addition. These results show that local aromaticity, as shown by NICS, can be used to predict and interpret addition sites for these systems. As a probe of their reactivity, the acidity is predicted for the C76H2 isomers and previously obtained results for C70H2 are rationalised.