To summarise, given the set of ligands shown in Figure the largest energy density one can hope to achieve with a singly or doubly substituted DHA molecules is about 0.5 kJ/g. But the half-life of the high energy states are much to short (sub-second) to be of practical use. The largest possible energy density for molecules with half-lives on the order of hours or greater is around 0.25 kJ/g.