Dual-mode dynamic phosphorescence modulation in bifunctional ligand-stabilized copper clusters for information encryption

Dynamic phosphorescence holds significant potential for practical applications. However, achieving precise regulation of dynamic luminescence (enhancement or quenching) presents considerable challenges. Herein, a terpyridine-modified bifunctional alkynyl ligand (EPTpy) stabilized copper cluster [Cu₃(dppm)₃(EPTpy)₂]PF₆ (Cu₃) was synthesized. The Cu₃ cluster, characterized by its terminal coordination sites, facilitates further chelation with Zn²⁺ to form a Cu₃-Zn cluster, resulting in a significant red-shift in emission from 535 to 620 nm. It is worth noting that their film quantum yields can be increased over 14-fold compared to crystals, reaching 47.33% (Cu₃) and 68.63% (Cu₃-Zn), respectively. Both clusters exhibit dynamic phosphorescence behavior, including phosphorescence quenching and enhancement. Specifically, the dynamic phosphorescence quenching originates from the strategically designed EPTpy ligand, triggered by radicals induced photochromism. On the other hand, dynamic photoactivated phosphorescence enhancement is achieved through rapid O₂ consumption via energy transfer between triplet states and molecular oxygen in PMMA thin films, facilitated by the bright emission, large k_ISC, and long intrinsic lifetime. Leveraging this tunable dynamic phosphorescence, a series of patterns was designed for applications in information encryption and storage. This work offers feasible approaches for regulating luminescence and advancing the understanding of the intriguing photophysical properties of clusters.