Enabling Thermally Stimulated Delayed Phosphorescence in Cu(I) Cyclic Trinuclear Complexes with Near-Unity Quantum Yield
Guo‐Quan Huang, Ri‐Qin Xia, Xu Chen, Yang Hu, Yong‐Liang Huang, Kun Wu, Ji Zheng, Weigang Lu, Dan Li
Abstract
Thermally stimulated delayed phosphorescence (TSDP) emission has recently been discovered in several Au(I)/Au(III) complexes, featuring thermally enhanced emission intensities and notable quantum yields (QYs). Developing earth-abundant metal-based TSDP emitters with further increased QYs holds significant promise for practical applications. Herein, we present a halogen bonding approach to achieve TSDP emission in bromo-substituted Cu(I) cyclic trinuclear complexes (CTCs). Photophysical analysis and theoretical calculations reveal the crucial role of halogen bonding in suppressing the excited-state distortions and reducing energy differences between the first and second triplet excited states (T 1 and T 2 ). This enables efficient spin-allowed reverse internal conversion, leading to the TSDP behavior. Additionally, the low internal reorganization energy and rigid halogen-bonded network in bromo-substituted Cu(I) CTCs result in significantly suppressed nonradiative decay and high QYs, with one approaching near-unity. This work provides an innovative approach to extend the TSDP behavior from Au(I)/Au(III) to Cu(I) complexes with high QYs.