In contrast to the variation of the LUMO energies, the electron density plot of the LUMO is identical in all five emitters (Figure ), having significant contribution from all carbon and nitrogen atoms except C2, C12c, and the central N8 (see Figure for numbering). The HOMO densities, however, form two distinct groups in their distribution. The HOMOs of 6NICz and 6,10NICz are symmetrically distributed in a three-tiered radial pattern around the central N2, while the HOMOs of 4NICz, 5NICz and 7NICz are perturbed away from this symmetry, forming more distinct lobes and overall possessing more nodal planes. Again, the electron density of 4NICz lies intermediate of the two patterns. The indole nitrogen has significant density in the HOMO but not the LUMO because of its conjugated lone pair. The peripheral pyridyl nitrogen is noticeably electron-accepting in 6NICz and 6,10NICz, having density only in the LUMO, while in 5NICz and 7NICz it has both accepting and donating character, reflected in contributions to both frontier molecular orbitals. In general, there is incomplete separation of the HOMO-LUMO densities in all five emitters, which results in both a larger S1 oscillator strength and ΔEST.