The steady-state PL and phosphorescence spectra of 4DMAC-TPPQ and 4PXZ-TPPQ in 2-MeTHF glass at 77 K were measured to ascertain the S1 and T1 levels from their respective onsets; the S1 and T1 levels of TPPQ were measured in methylcyclohexane (MCH) at 77 K to mitigate against possible photochromism in 2-MeTHF (Figure ). In glassy MCH, the lPL of TPPQ is around 456 nm, while the delayed emission spectrum of TPPQ, attributed to phosphorescence, peaks at 766 nm. Notably, there is a weak residual prompt emission at around 460 nm. The corresponding S1 and T1 energies are 2.82 and 1.85 eV, and thus the DEST is 0.97 eV. The S1 and T1 energies of 4DMAC-TPPQ are 2.26 and 1.85 eV, while for 4PXZ- TPPQ they are 2.08 and 1.84 eV (Figure ). Thus, in these two compounds the S1 energies follow the trend calculated by DFT and the observed HOMO-LUMO gaps determined by electrochemistry, while the T1 energies, which are effectively the same as that of TPPQ, reflect the same 3 LE state. The corresponding ΔEST values of 4DMAC-TPPQ and 4PXZ-TPPQ are 0.41 and 0.24 eV, respectively.