Exohedral functionalization of the icosahedral cluster Si20H20: a density functional theory study

We report results of density functional theory calculations on three derivatives of the recently predicted hydrogenated silicon fullerene cluster Si20H20 using the B3PW91 hybrid exchange-correlation functional with the 6-311+G(d) basis set. The cluster has been exohedrally functionalized by replacing one of its H atoms with –CH2OH, –COOH, and –CONH2. The resulting functionalized clusters have nearly the same HOMO–LUMO gaps as that of the perhydrogenated silicon fullerene leading to the possibility of developing new silicon fullerene-based molecules for medico-biological applications. The deprotonated Si20H19(COO−) cluster displays a very large permanent dipole moment along with a strongly localized HOMO on its carboxyl group.