Fig. 2. Theoretical calculations and intermolecular packing analysis of BT-Cl, BT-CF3SO3, and BT-F5-TBP. (a) Calculated intermolecular distances for BT-Cl, BT-CF3SO3, and BT-F5-TBP. (b) Frontier molecular orbital distributions (HOMO and LUMO) of BT-Cl, BT-CF3SO3, and BT-F5-TBP obtained at the PBE0/def2-TZVP level based on the optimized geometries. The excitation energies of the triplet excited states were calculated using time-dependent density functional theory (TD-DFT) at the same level of theory. The corresponding energy gaps (ΔEgap and ΔEST) between singlet and triplet states are also presented in the figure.
