The electronic properties of the four iridium complexes along with the previously reported mer-Ir(tfpmi)3 and its facial isomer fac-Ir(tfpmi)3 were investigated using density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations. All calculations were performed using the B3LYP functional and the 6-31G(d,p) basis set for non-metal atoms and the SBKJC VDZ ECP basis set for the Ir atom, using the conductor-like polarizable continuum model (CPCM) for acetonitrile solution. This level of theory has previously been shown to provide accurate predictions of energy levels for iridium complexes. The optimised ground state structures match those determined crystallographically (Table ). The calculated frontier orbitals and excited states of the fac isomers are very similar to those of the mer isomers (Figure and Table ), with a very small increase (10-30 meV) in both the HOMO-LUMO gap and excited state energies, behavior that is reproduced experimentally (vide infra). This behavior is in contrast to the previously reported pairs of mer/fac isomers of Ir(C^C)3 complexes [Ir(pmp)3, Ir(dmpmp) 3 and Ir(pmpz)3] in which the mer isomer is calculated to have a destabilised HOMO, stabilised LUMO and lower excited state energies in comparison to the fac isomer. The HOMO is distributed across the iridium centre and the C^C ligands, while the LUMO is localized only on the C^C ligands. The bulky Bn and tmBn substituents are not involved in the frontier MOs, the energy of the orbitals and excited states are similar to those of the previously reported mer/fac-Ir(tfpmi)3. The T1 state is of a predominantly ligand-centred character mixed with some metal-to-ligand charge transfer character (LC/MLCT). A large degree of MLCT character in the excited states would be revealed in the reduced singlet-triplet energy gap (ΔEST) between the states. The large ΔEST of 0.45 to 0.48 eV for these complexes supports the assignment of significant LC character to the T1 excited state. The singlet and triplet state mixing is thus mostly the result of the high level of SOC due to the heavy metal in these iridium complexes. Optimisation of the triplet state geometry of the complexes revealed only minimal structural changes compared to their ground state structures, with only a notable contraction in the Ir-CAr distance for one of the ligands by between 0.040 and 0.077 Å. Visualisation of the triplet spin density distribution (Figure ) reveals that it is concentrated on the same C^C ligand that contains the shortened Ir-CAr bond. TD-DFT calculations show that there are three nearly degenerate triplet energy levels, with T1 and T3 separated by between 27 and 74 meV.