The corresponding optical bandgaps, determined from the intersection point of the normalized absorption and emission spectra, for DMACBP, DMACPyBP, DMACBPN and DMACPyBPN are 2.37 eV, 2.20 eV, 2.31 eV and 2.12 eV, respectively (Figure ), which is consistent with the trend in emission energies (Figure and Table ). The photoluminescence quantum yields (FPL) for DMACBP, DMACPyBP, DMACBPN and DMACPyBPN in degassed toluene solution are 35%, 20%, 38% and 6%, respectively. When exposed to oxygen, these values significantly decrease to 9%, 7%, 8%, and 3% respectively. The energies of the onsets of the prompt fluorescence and phosphorescence spectra in 2-MeTHF glass at 77 K were used to determine the S1 and T1 energies (Error! Reference source not found.c). The S1 energies are 2.37, 2.26, 2.34 and 2.20 eV, while the T1 energies are 2.35, 2.26, 2.32 and 2.20 eV, for DMACBP, DMACPyBP, DMACBPN and DMACPyBPN, respectively. As both the prompt fluorescence and phosphorescence spectra are structureless, it is reasonable to assign both the S1 and T1 states as possessing significant CT character.