Although all substituted pentalenides investigated possessed a similar HOMO-LUMO gap of 3.1-3.5 eV, comparison of the absolute energy levels of unsubstituted 1 versus the tetraphenyl-substituted 2 showed how the aryl moieties stabilise the frontier orbitals through conjugation with the dianionic core (Figure top; Table ). Moving from the Ph4 substitution pattern in 2 to Tol4 in 3 slightly raised the energy levels due to the +I effect of the p Me groups.