近日，清华大学教授马冬昕及其研究小组研究出基于铱（III）配合物自组装可逆激发态转换的结构刚性策略，用于多刺激响应数据加密。2024年10月15日，国际知名学术期刊《美国化学会杂志》发表了这一成果。

据介绍，刺激响应色材料在特定的外部刺激下表现出颜色切换特性，在各个领域得到了广泛的研究。由于过渡金属配合物的激发态不仅取决于其化学成分，而且受分子间堆叠模式的影响，因此作为刺激响应变色材料的候选物具有很大的应用潜力。由于八面体结构的有序堆积存在固有的困难，改变铱（III）配合物的多重刺激响应的堆积模式仍然是一个主要挑战。

在这项工作中，课题组人员提出了一种基于自组装的结构固化策略来可逆地调节铱（III）配合物的激发态，从而实现不同刺激条件下的颜色切换。该研究团队通过四（全氟苯基）硼酸盐（[B(PhF₅)₄]）制备阳离子铱（III）配合物，作为反离子，其匹配的四面体构型和缺电子芳构性使其与八面体铱（III）阳离子极性-π相互作用，诱导自组装形成结构刚性。

结构刚性限制了金属-配体电荷转移（3MLCT）激发态的大构象变化，促进了聚集态下3MLCT向配体中心（3LC）激发态的转化。激发态转换导致光致发光光谱中的54 nm蓝移（从黄色到天蓝色）。因此，课题组研究人员报道了一系列对低温、蒸汽发烟和机械力具有不同响应的阳离子铱（III）配合物，从而实现了多重刺激响应的数据加密。他们的工作为实现八面体配合物的有序堆叠提供了一种新策略，显示了对过渡金属配合物的光物理过程的更深入的理解，并为开发多刺激响应的铬材料提供了新的视角。

附：英文原文

Title: Structural Rigidification Strategy Based on Self-Assembly Enabled Reversible Excited-State Conversion of Iridium(III) Complexes for Multiple-Stimulus-Responsive Data Encryption

Author: Xiangyu Liu, Jing Liu, Danlei Zhu, Xinghua Yan, Jiawei Chen, Lian Duan, Yuetong Kang, Dongxin Ma

Issue&Volume: October 15, 2024

Abstract: Stimulus-responsive chromic materials exhibit color-switching properties under specific external stimuli and have been widely used in various fields. Transition-metal complexes show great potential applications as promising candidates for stimulus-responsive chromic materials, as their excited states not only depend on the chemical composition but are also affected by the intermolecular stacking modes. Owing to the intrinsic difficulty in the ordered stacking of the octahedral configuration, changing the stacking modes of iridium(III) complexes for multiple-stimulus responsiveness remains a significant challenge. In this work, we propose a structural rigidification strategy based on self-assembly to reversibly regulate the excited states of iridium(III) complexes, therefore achieving color switch under different stimulus conditions. We prepare cationic iridium(III) complexes by using tetrakis(perfluorophenyl)-borate ([B(PhF5)4]) as the counterion, whose matching tetrahedral configuration and electron-deficient aromaticity enables polar-π interaction with the octahedral iridium(III) cations, inducing self-assembly to form structural rigidification. The structural rigidity restricts the large conformational changes of the metal-to-ligand charge transfer (3MLCT) excited state, and facilitates the conversion from the 3MLCT to the ligand-center (3LC) excited state in aggregated states. The excited-state conversion results in a 54 nm blue shift (from yellow to sky blue) in the photoluminescence spectra. As a result, we report a series of cationic iridium(III) complexes with different responses to low temperature, vapor fuming, and mechanical force, therefore achieving multiple-stimulus-responsive data encryption. Our work provides a novel strategy to achieve ordered stacking of octahedral complexes, shows a deeper understanding of the photophysical processes of transition-metal complexes, and offers a new perspective to develop multiple-stimulus-responsive chromic materials.

DOI: 10.1021/jacs.4c12454

Source: https://pubs.acs.org/doi/abs/10.1021/jacs.4c12454