Dynamic Phosphorescence Behavior of Carbene-Metal-Amide Complexes from the Perspective of Excited State Modulation

Abstract

Carbene-metal-amide (CMA) complexes have diverse applications in luminescence, imaging and sensing. In this study, we designed and synthesized a series of CMA complexes, which were subsequently doped into a PMMA host. These materials demonstrate light-induced dynamic phosphorescence, attributed to their long intrinsic triplet state lifetime (τ_P,int, in the μs-ms scale), high intersystem crossing (ISC) rate constant (k_ISC, up to 10⁷ s⁻¹), and bright phosphorescence. The extended τ_P,int, and elevated k_ISC facilitate efficient sensitization of singlet oxygen (¹O₂) under light irradiation, which is rapidly consumed by the host material, creating a localized anaerobic environment conducive to bright phosphorescence emission. The S_n-T₁ process exhibits a large spin-orbital coupling matrix element (SOCME) value, while the SOCME value between T₁ and S₀ is comparatively smaller, resulting in a large k_ISC and long τ_P,int, Computational results indicate that the hole-electron configuration in the lowest triplet state exhibits low contributions from gold. Based on the dynamic phosphorescence properties, an encryption material capable of achieving a “burn after reading” effect was developed. This work illustrates that those phosphorescent emitters with minimal heavy atom contribution can produce dynamic phosphorescent phenomena, providing a novel strategy for designing stimuli-responsive phosphorescent materials.