The 4f‐4f emissions from lanthanide trication (Ln3+) complexes are widely used in bioimaging probes. The emission intensity from Ln3+ depends on the surroundings, and thus, the design of appropriate photo‐antenna ligands is indispensable. In this study, we focus on two probes for detecting hydrogen peroxide, for which emission intensities from Tb3+ are enhanced chemo‐selectively by the H2O2‐mediated oxidation of ligands. To understand the mechanism, the Gibbs free energy profiles of the ground and excited states related to emission and quenching are computed by combining our approximation—called the energy shift method—and density functional theory. The different emission intensities are mainly attributed to different activation barriers for excitation energy transfer from the ligand‐centered triplet (T1) to the Tb3+‐centered excited state. Additionally, quenching from T1 to the ground state via intersystem crossing was inhibited by intramolecular hydrogen bonds only in the highly emissive Tb3+ complexes. © 2018 Wiley Periodicals, Inc.

中文翻译：

---

基于镧系元素的体内发光探针检测过氧化氢的理论研究

镧系元素三阳离子 (Ln3+) 复合物的 4f-4f 发射广泛用于生物成像探针。Ln3+ 的发射强度取决于周围环境，因此，设计合适的光天线配体是必不可少的。在这项研究中，我们专注于检测过氧化氢的两种探针，通过 H2O2 介导的配体氧化选择性地增强了 Tb3+ 的发射强度。为了理解该机制，通过结合我们的近似值（称为能量转移方法）和密度泛函理论，计算与发射和猝灭相关的基态和激发态的吉布斯自由能分布。不同的发射强度主要归因于激发能量从以配体为中心的三重态 (T1) 到以 Tb3+ 为中心的激发态的不同激活势垒。此外，通过系统间交叉从 T1 到基态的猝灭仅在高发射性 Tb3+ 复合物中受到分子内氢键的抑制。© 2018 Wiley Periodicals, Inc.