The optimized geometries of the ground and excited states, and the electronic structures of dBr-tBu-DiKTa, tBr-DiKTa, and Mes3-DiKTa were first calculated using Density Functional Theory (DFT) and time-dependent DFT (TD-DFT) within the Tamm-Dancoff approximation (TDA) at the PBE0/6-31G(d,p) level of theory in the gas phase. As shown in Figure , the LUMO of these materials is located on the DiKTa core. The HOMOs are likewise distributed over the DiKTa core, and with contributions from the bromine substituents in dBr-tBu-DiKTa and tBr-DiKTa. There are four low-lying triplet states near or below S1, which are implicated in facilitating RISC. Thus, we calculated the SOC matrix elements (SOCME) for S1-T1, S1-T2, S1-T3, and S1-T4 transitions based on the optimized T1 geometries.