Achieving Dual Emission of Fluorescence and Phosphorescence from Anti-Kasha’s Metal–Organic Halides for Information Encryption

Luminescent materials typically emit their fluorescence or phosphorescence at a specific wavelength with different excitation energies via the so-called Kasha's rule. If fluorescence or phosphorescence emission via anti-Kasha's rule could be achieved, it will hold great promise for applications in many fields. In this work, we report the synthesis and characterization of new metal–organic halide materials with dual emission of efficient room-temperature phosphorescence and fluorescence, which obey anti-Kasha's rule. Here, three emitting metal–organic halides with formula ZnX2(bidpe) (X = Cl for 1, X = Br for 2, X = I for 3, bidpe = 4,4′-bis(imidazol-1-yl)diphenyl ether) were prepared and their photophysical properties were investigated. The complexes exhibit dual emission of fluorescence and phosphorescence via anti-Kasha's rule, and their RTP properties of resultant products are modulated by halide substitution synthesis. DFT calculations indicate that the singlet states exhibit a halide–ligand charge transfer (XLCT) character while the triplet states are dominated by the intraligand π–π* transitions. Furthermore, the multilevel information encryption and anticounterfeiting applications are developed by virtue of anti-Kasha's rule emission.