Multi-Dimensional Color Tunable Long Persistent Luminescence in Metal Halide-Based CPs Through Precise Manipulation of Electronic and Steric Effects

Regulating strategies for long persistent luminescence (LPL) are always in high demand. Herein, a series of coordination polymers (CPs) (SUST-Z1-Z4) are fabricated using 1,10-phenanthroline derivatives involving different substituents (─H, ─CH₃, ─Cl, and ─Br) as ligands, respectively. Crystallographic data demonstrate that these CPs adopt alternating arrangements of cadmium halide chains and π-conjugated ligands. Cadmium halide chains not only bring about heavy atom effects but also introduce abundant intermolecular interactions, including halogen bonding and π-π stacking, favoring the generation of stable triplet excitons. Additionally, distinct substituents featured different electron-withdrawing abilities give rise to various spatial resistances between Phen planes, thereby resulting in diverse molecular packing modes and electronic structures. Thus, their aggregated state phosphorescence lifetimes range from 6.84 ms (SUST-Z4) to 91.10 ms (SUST-Z2), and the colors are modulated from orange to red at room temperature. SUST-Z2 presents the longest-lasting RTP and the most obvious red LPL, which is derived from the weakest electron-withdrawing capability of ─CH₃ in ligands. Moreover, owing to the co-existence of single molecule and aggregated triplet excitons, these CPs also realize dynamic color-tunable LPL from green/orange to yellow/red depending on the excitation wavelength, temperature, and time-evolution. Based on quite different LPL of these CPs, multiple anti-counterfeiting methods are proposed.