Comparing the frontier orbitals and their energies across the series further illustrates the electronic influence of the substituents on the pentalenide (Figure top). In the HOMO of each compound investigated the largest contribution was found in the 1,3,4,6 position, and in the arylated systems some delocalisation into the aryl substituents could be seen (Figure bottom). The corresponding LUMO showed even stronger delocalisation into the aryl moieties.