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

Abstract

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 (³XMCT) and copper-centered 4d→3s, 3p transitions, whereas the HE emission originates from a triplet halide-to-ligand charge-transfer (³XLCT). Importantly, in complex 2, the strong C—H∙∙∙Cl interaction in the supramolecular crystal lattice annihilated the sensitive cluster centered (³CC) 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.