The Ph2-substituted 9 and the p FPh2-substituted 10 had a slightly higher HOMO energy than 2, resulting in reduced HOMO-LUMO gaps (3.06 eV for 9 and 3.08 eV for 10). Comparing the raised frontier orbital energies of Ph3Me-substituted 12 with those of Ph4-substituted 2 again demonstrates the +I effect of the Me group.