Ultralong Afterglow in Zero‐ and One‐Dimensional Cd(II) Halide Complexes with Differential Arrangement of N ‐Methylbenzimidazole Ligands

In this work, 1D Cd(II) halide chain (Cd(Bz)Br) and mononuclear Cd(II) halide complex (Cd(Bz)I) were obtained by regulating halide ions. Br⁻ ions act as µ₂-Br bridges, alternately connecting with Cd(II) ions to form the trunks of the 1D chains with repeating units of -[Cd-Br₂]-. The outer edges of the branches contain anti-parallel N-methylbenzimidazole (Bz) planes, which are coordinated with the Cd(II) ions. Notably, the anti-parallel Bz planes between adjacent Cd(Bz)Br chains are tightly interlocked through π-π interactions, forming a "zipper"-like connection, which promotes the intersystem crossing process and stabilizes the excited triplet. These results in room-temperature ultralong afterglow from Cd(Bz)Br with a lifetime of 34.35 ms and a delay time of up to 0.7 s. Furthermore, the butterfly-shaped mononuclear complex Cd(Bz)I exhibits a room-temperature phosphorescence (RTP) lifetime of only 5.86 ms, with an afterglow duration of less than 0.1 s. By leveraging the significant differences in the RTP of these Cd(II) halide complexes, a complex anti-counterfeiting system with multiple encryption features was constructed. This work not only provides a vivid example of manipulating halide ions to expand the range of Cd(II) halide complexes in different dimensions but also opens new horizons for regulating the RTP of Cd(II) halide complexes.