Zhou Yanyan, Li Hongfeng, Zhu Tianyu, Gao Ting, Yan Pengfei
Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, School of Chemistry and Materials Science , Heilongjiang University , Harbin 150080 , People's Republic of China.
J Am Chem Soc. 2019 Dec 18;141(50):19634-19643. doi: 10.1021/jacs.9b07178. Epub 2019 Dec 5.
Chiral lanthanide cages with circularly polarized luminescence (CPL) properties have found potential application in enantioselective guest recognition and sensing. However, it still remains a big challenge to develop a simple and robust method for the diastereoselective assembly of homochiral lanthanide cages in view of the large lability of the Ln(III) ions. Herein, we report the first example of the formation of a enantiopure lanthanide tetrahedral cage via a chiral ancillary ligand induction strategy. One such cage, (EuL)(R/S-BINAPO), is assembled by four achiral -symmeric tris(β-diketones) (4,4',4″-tris(4,4,4-trifluoro-1,3-dioxobutyl)triphenylamine, L) as faces, four Eu(III) ions as vertices and four chiral -/-bis(diphenylphosphoryl)-1,1'-binaphthyl (R/S-BINAPO) as ancillary ligands. X-ray crystallography and NMR and CD spectra confirm the formation of a pair of enantiopure chiral topological tetrahedral cages, (EuL)(R-BINAPO) and (EuL)(S-BINAPO) (ΔΔΔΔ- and ΛΛΛΛ-). As expected, the tetrahedral cages present strong CPL with || values up to 0.20, while they unexpectedly give ultrahigh luminescent quantum yields (QYs) of up to 81%, the highest value reported in chiral Ln(III) complexes. More impressively, the chiral memory effect for a lanthanide-based assembly is observed for the first time. The chirality of the original cage framework is retained after R/S-BINAPO is replaced by the achiral bis[2-(diphenylphosphino)phenyl] ether oxide (DPEPO), and thus another pair of enantiopure Eu(III) tetrahedral cages, ΔΔΔΔ- and ΛΛΛΛ-[(EuL)(DPEPO)] (ΔΔΔΔ- and ΛΛΛΛ-), have been isolated. Encouragingly, cage also presents an impressive luminescence quantum yield (QY = 68%) and intense CPL (|| = 0.11). This study offers a simple and low-cost synthesis strategy for the preparation of lanthanide cages with CPL properties.
具有圆偏振发光（CPL）特性的手性镧系金属笼在对映选择性客体识别与传感方面具有潜在应用价值。然而，鉴于Ln(III)离子的高活性，开发一种简单且可靠的方法用于非对映选择性组装纯手性镧系金属笼仍然是一个巨大的挑战。在此，我们报道了通过手性辅助配体诱导策略形成对映纯镧系四面体笼的首个实例。其中一个这样的笼，(EuL)(R/S-BINAPO)，由四个非手性的对称三（β-二酮）（4,4',4″-三（4,4,4-三氟-1,3-二氧代丁基）三苯胺，L）作为面、四个Eu(III)离子作为顶点以及四个手性的 -/-双（二苯基磷酰基）-1,1'-联萘（R/S-BINAPO）作为辅助配体组装而成。X射线晶体学、核磁共振和圆二色光谱证实形成了一对对映纯的手性拓扑四面体笼，(EuL)(R-BINAPO)和(EuL)(S-BINAPO)（ΔΔΔΔ-和ΛΛΛΛ-）。正如预期的那样，四面体笼呈现出强烈的CPL，其||值高达0.20，同时它们意外地给出了高达81%的超高发光量子产率（QYs），这是手性Ln(III)配合物中报道的最高值。更令人印象深刻的是，首次观察到基于镧系元素组装体的手性记忆效应。在用非手性的双[2-（二苯基膦基）苯基]醚氧化物（DPEPO）取代R/S-BINAPO后，原始笼框架的手性得以保留，因此分离出了另一对对映纯的Eu(III)四面体笼，ΔΔΔΔ-和ΛΛΛΛ-[(EuL)(DPEPO)]（ΔΔΔΔ-和ΛΛΛΛ-）。令人鼓舞的是，笼 也呈现出令人印象深刻的发光量子产率（QY = 68%）和强烈的CPL（|| = 0.11）。这项研究为制备具有CPL特性的镧系金属笼提供了一种简单且低成本的合成策略。
