Fig. 2. Photophysical properties of Ce-1 in solution and as crystalline powder.

a UV–Vis absorption spectra of Ce-1 and KTp^Me2 in solution (DCM, 10⁻⁵ M), and PL spectra of Ce-1 in solution (DCM, 10⁻⁵ M) and as crystalline powder at room temperature (RT) and 77 K. The excitation wavelength is 370 nm. Inset, photographs of the complex in solution and as crystalline powder under 365 nm irradiation. b Transient PL decays of the complex in solution and as crystalline powder at room temperature and 77 K. The excitation wavelength is 375 nm. Inset, schematic diagram to illustrate the PL mechanism of the cerium(III) complex, where Abs, IC, and PL represent absorption, internal conversion, and photoluminescence, respectively. ²D_3/2 is the lowest excited state of the Ce³⁺ ion. ²F_5/2 and ²F_7/2 are two ground levels of the Ce³⁺ ion