We first analyzed the computed spectra of the napththyl-containing Cu Mes MIC Naph Cz, Cu 3,5-MePh MIC Naph Cz, and Cu Mes MIC Naph NPh2 complexes since all of them show similar vibronic progression in the experimental emission spectra, with marked peaks consistent with LE states. In the case of Cu Mes MIC Naph Cz, the simulated phosphorescence spectrum centered at 526 nm closely matches the experimental data, whereas the fluorescence spectrum does not (Figure ). The simulated vibronic progression with a peak separation of 29 nm is in good agreement with the experimental value of 30 nm, which corresponds to a normal mode at 1380 cm - 1 centered on the naphthyl group. In contrast, the simulated fluorescence spectrum shows a peak at 332 nm, which is blue-shifted by ca. 194 nm compared to the experimental data, which is a large error, even for TD-DFT/TDA standards. Thus, we propose that the emission observed from Cu Mes MIC Naph Cz corresponds to a T1 to S0 phosphorescence. For Cu Mes MIC Naph NPh2, as explained above, the experimental emission spectrum shows both a Gaussian-shaped band at 399 nm with a second band having a vibronic progression starting with a peak at 496 nm (Figure ). Interestingly, the computed spectra for a S1 to S0 relaxation is a good match with the former, whereas the computed spectrum corresponding to a T1 to S0 transition correlates well with the latter Regarding the vibronic structure, the simulated spectra display a coupling of 29 nm, only slightly larger than the experimental one of 26 nm. Finally, for Cu 3,5-MePh MIC Naph Cz, the experimental emission peaks at 440 nm (Figure ), whereas the simulated fluorescence spectrum has a peak at 342 nm, while the modelled phosphorescence one exhibits a vibronic progression starting at 448 nm, neither of which is a good match; it is not possible for us to conclude the origins of the emission in this specific case.