Temperature-dependent lifetime studies (Figures and) reveal that the delayed emission is not thermally activated, providing further evidence that the origin of the long-lived luminescence at 470 nm results from RTP and not from TADF; in fact, only at 77 K is there a slight decrease in the excited state lifetime (Figure ), which is attributed to the significantly suppressed T 1 H emission (Figure ). Phosphorescence emission at 200 K measured at different time-gated windows indicates variable excited-state dynamics (Figure ), also implying the existence of The picture for PTZ-Nap is different. The steady-state PL under air is blue-shifted and structured, centered at 400 nm, characteristic of emission from an LE state; notably, there is also a broad emission tail (Figure ). The emission lifetime is 5.19 ns (Figure ). When placed under vacuum at 298 K, the structured emission beyond 475 nm is strengthened, which is strongly enhanced at 77 K. RTP emission can be observed in the range of 450-650 nm (Figure ), with an associated t ph of 66.7 ms. The LTP at 77 K has a similar emission but narrower profile compared to the RTP; however, the t ph (628 ms) is much longer (Figure and Table ). Similar RTP and LTP afterglows indicate essentially two degenerate triplet states (Figure ). Temperature-dependent photophysical investigations also reveal essentially indistinguishable T 1 H and T 1 L (Figure ).