Achieving tunable long persistent luminescence in metal organic halides based on pyridine solvent

The research of long persistent luminescence (LPL) materials has yield brilliant results in many fields. However, the efforts are still needed for the regulation of the LPL performance. In this work, a series of LPL metal organic halides with rich halogen-bond interactions, Py-CdX2 (X = Cl, Br, I) were synthesized through self-assembly by CdX2 and pyridine solvent. The steady-state emission redshifted and phosphorescence lifetime declined as the halogen atoms are aggravated. Three halides exhibit adjustable emission from blue to green and multiple phosphorescence from green to yellow at room temperature by changing the excitation wavelengths. Surprisingly, Py-CdX2 can emit the visible color-tunable LPL from green to yellow after removing different excitation sources at ambient conditions. Combing the results of theoretical calculation and experimental analysis, it is found that heavy atom effect and the rich intermolecular halogen bond help realize LPL and multiple triplet states originated from the pyridine ring and the halogens.