Liu Xiangyu, Liu Jing, Zhu Danlei, Yan Xinghua, Chen Jiawei, Duan Lian, Kang Yuetong, Ma Dongxin
Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University Beijing 100084, P. R. China.
Center of Basic Molecular Science (CBMS), Department of Chemistry, Tsinghua University, Beijing 100084, P. R. China.
J Am Chem Soc. 2024 Oct 30;146(43):29955-29963. doi: 10.1021/jacs.4c12454. Epub 2024 Oct 15.
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(PhF)]) 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 (MLCT) excited state, and facilitates the conversion from the MLCT to the ligand-center (LC) 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.
刺激响应型变色材料在特定外部刺激下表现出颜色切换特性，已被广泛应用于各个领域。过渡金属配合物作为刺激响应型变色材料的有前途的候选者显示出巨大的潜在应用，因为它们的激发态不仅取决于化学成分，还受分子间堆积模式的影响。由于八面体构型有序堆积存在内在困难，改变铱（III）配合物的堆积模式以实现多刺激响应仍然是一个重大挑战。在这项工作中，我们提出了一种基于自组装的结构刚性化策略，以可逆地调节铱（III）配合物的激发态，从而在不同刺激条件下实现颜色切换。我们使用四（全氟苯基）硼酸根（[B(PhF)]）作为抗衡离子制备阳离子铱（III）配合物，其匹配的四面体构型和缺电子芳香性能够与八面体铱（III）阳离子形成极性-π相互作用，诱导自组装形成结构刚性化。结构刚性限制了金属到配体电荷转移（MLCT）激发态的大的构象变化，并促进了聚集态下从MLCT激发态到配体中心（LC）激发态的转变。激发态的转变导致光致发光光谱出现54 nm的蓝移（从黄色变为天蓝色）。结果，我们报道了一系列对低温、蒸汽熏蒸和机械力有不同响应的阳离子铱（III）配合物，从而实现了多刺激响应数据加密。我们的工作提供了一种实现八面体配合物有序堆积的新策略，对过渡金属配合物的光物理过程有了更深入的理解，并为开发多刺激响应型变色材料提供了新的视角。
