Solvent‐Mediated Stimuli Responsive Phosphors Based on Phosphine‐Copper Iodide Hybrid Complexes for Information Encryption

Comprehensive Summary Stimuli responsive phosphors with photoluminescence and thermoresponsive luminescence are intriguing for information encryption applications. Herein, two solvent‐mediated, stimuli responsive phosphors based on phosphine‐copper(I) iodide complexes 1 and 2 are reported. Complex 1 exhibited temperature‐ and excitation‐wavelength‐dependent dual‐emission characteristics, displaying high energy (HE) and low energy (LE) bands with the quantum yield (QY) of 38.5% under 365 nm irradiation; but complex 2 exhibited no emission. The LE emission can be attributed to a triplet halide‐to‐metal charge transfer ( 3 XMCT) and copper‐centered 4d→3s, 3p transitions, whereas the HE emission originates from a triplet halide‐to‐ligand charge‐transfer ( 3 XLCT). Importantly, in complex 2 , the strong C—H∙∙∙Cl interaction in the supramolecular crystal lattice annihilated the sensitive cluster centered ( 3 CC) excited state. Intriguingly, only the HE emission band of complex 2 can be successfully activated by high‐energy excitation or changing the temperature. Nevertheless, the QY of complex 2 is 15.6% under 310 nm irradiation, which is smaller than that of complex 1 of 49.8%. This behavior was further confirmed by heating, where both complexes show HE emission. The reversible crystal transformation between complexes 1 and 2 was achieved. Furthermore, the reversible excitation‐wavelength‐dependent dual‐emission and thermoresponsive properties make these phosphors suitable candidates for anti‐counterfeiting and information encryption applications.