The FPL values of the compounds in oxygen-free toluene are comparable at 18, 14 and 15% for 4TABN1, 5TABN2 and 6TABN3, respectively. All three compounds show broad and structureless PL spectra that are characteristic of emission from CT states. The emission maxima vary narrowly from 2.71 to 2.76 eV (from 458 to 449 nm) as do the onset of the spectra, varying from 2.96 to 2.98 eV. For reference, the transient PL decays for the series in toluene are presented in Figure . For all three compounds, the prompt fluorescence has an identical decay of about 2.5 ns. The lifetime of the delayed fluorescence at room temperature is also very similar and about 100 ns, with a slow tail suggesting the presence of some triplettriplet annihilation. We next cooled the solution to 77 K (Figure ) to ascertain the ΔEST gaps from the difference in energy from the onsets of the prompt fluorescence and phosphorescence spectra. u.)