provided insight that incorporation of an electron-withdrawing group (pyridine, pyridinium, and methyl pyridinium) can not only affect the HOMO/LUMO distribution and energies but also tune the singlet-triplet energy gap (ΔEST). For the proposed molecule N-methylaza-[8]CPP + , where a methyl pyridinium unit is incorporated into the CPP skeleton and used as an electron-acceptor, the DFT calculations showed that the LUMO of N-methylaza-[8]CPP + is located on the methyl pyridinium unit as well as the adjacent benzene rings and the HOMO is located across the remaining benzene rings, while for the reference [8]CPP, the HOMO, and LUMO are delocalized over the whole molecule. As a result, the ΔEST was predicted to decrease from 0.50 eV for [8]CPP to 0.23 eV for N-methylaza-[8]CPP + . This is the first evidence for the potential of this class of compounds to exhibit thermally activated delayed fluorescence (TADF), where a small ΔEST is required to promote reverse intersystem crossing (RISC) at ambient temperatures. TADF compounds have generated much interest as these can be used as emitters in electroluminescent devices that are capable of harvesting both singlet and triplet excitons and their conversion to light. When the RISC occurs from the lowest excited triplet (T1) to the lowest excited singlet (S1) states, the RISC