The resulting DFT storage densities and free energy barrier heights are shown in Table 1 for the five molecules with largest storage density. The best five are all predicted to have an almost two-fold increase in storage density (0.24-0.25 kJ/g) compared to the parent system. Of the five, all but one have predicted back reaction-barriers that are between 4.7 and 16.5 kJ/mol higher than the parent compound.