Next, the energies of the frontier molecular orbitals were inferred from the electrochemical behavior of PXZ-Nap and PTZ-Nap, measured using cyclic voltammetry (CV) and differential pulse voltammetry (DPV), in deaerated DMF with 0.1 M tetra-n-butylammonium hexafluorophosphate as the supporting electrolyte. The oxidation/reduction potentials (E ox /E red ) of PXZ-Nap and PTZ-Nap determined from the DPV peaks are 0.79 eV/-2.09 eV and 0.78 eV/-2.09 eV vs SCE, respectively (Figure ). Thus, PXZ-Nap and PTZ-Nap show similar HOMO values of -5.14 eV and -5.13 eV, respectively, despite the different donors, and the same LUMO value of -2.26 eV (Table ), the result of the LUMO being localized on the Nap core. The results at first did not seem to align with the gas phase calculations (Figure ). However, a closer inspection of the DFT calculations of PTZ-Nap, now employing a DMF continuum model, indicates that a quasi-axial conformer is responsible for the destabilized HOMO (Figure ); indeed, accessible quasi-equatorial and axial conformations of PTZ have been previously reported. Okazaki et al. have also reported a series of PTZ-containing molecules that exists in different conformations, with corresponding HOMO values that vary from -5.59 eV to -5.20 eV. The UV-vis absorption spectra show a weak CT transition at around 400 nm for both compounds (Figure ). The optical gaps (E g ) of PXZ-Nap and PTZ-Nap estimated from the onset of absorption spectra in toluene are 2.92 eV and 3.10 eV, respectively, which are almost same values as those measured in DMF (~3.1 eV). We hypothesized that variation in E g is caused by the existence of different conformers. The CT character of the emissive excited state was evidenced from the positive solvatochromism of the photoluminescence (PL) spectra (Figure and) and the accompanied increased PL lifetimes (Figure , Table ). We next investigated the photophysical properties of PXZ-Nap and PTZ-Nap in PMMA at 1 wt% doping. At this low doping concentration intermolecular interactions will only negligibly affect triplet excited dynamics while the impregnation of the emitters in a solid-state matrix will serve to suppress non-radiative decay. The steady-state PL spectra of PXZ-Nap in air and under vacuum (at 298 K) are broad, unstructured, and centered at 470 nm, which are characteristic of emission from a CT state (Figures 3a). At 77 K, there is the emergence of a second emission band at ~510 nm that is assigned to phosphorescence. The PL lifetime of PXZ-Nap under vacuum is 7.55 ns (Figure , Table ). Time-gated PL measurements (10 ms delay) detected the RTP spectrum of PXZ-Nap (Figure ), which is centered also around 470 nm but is narrower and its decay has an associated t ph of 83.3 ms (Figure ). Such a long lifetime rules out thermally activated delay fluorescence (TADF) as the origin of this delayed emission. The low-temperature phosphorescence (LTP) emission at 77 K is centered at 520 nm and possesses a slightly structured character, implying emission from a state with dominant LE character, which coincides with the calculations (Figure ). The differences in energy of the RTP and LTP suggest that they originate from two distinct conformers. Indeed, the blue RTP (T 1 H ) and green LTP (T 1 L ) afterglows provide stark evidence of emission from two different T 1 states (Figure ). Temperature-dependent steady-state PL and phosphorescence studies show the gradually red-shifted and intensified emission band centered at 525 nm (Figures 4a) and red-shifted phosphorescence emission (Figure ), respectively, further demonstrating that temperature is the key to excitonic communication between T 1 H and T 1 L . The related Commission Internationale de l'Éclairage (CIE) diagrams also reflect the gradual emission color change with changing temperature (Figures and).