State Key Laboratory of Chirosciences, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong.
Department of Chemistry, Durham University, South Road, Durham, DH1 3LE, UK.
Nat Commun. 2017 Oct 24;8(1):1128. doi: 10.1038/s41467-017-01025-1.
Predictable stereoselective formation of supramolecular assembly is generally believed to be an important but complicated process. Here, we show that point chirality of a ligand decisively influences its supramolecular assembly behavior. We designed three closely related chiral ligands with different point chiralities, and observe their self-assembly into europium (Eu) tetrametallic tetrahedral cages. One ligand exhibits a highly diastereoselective assembly into homochiral (either ΔΔΔΔ or ΛΛΛΛ) Eu tetrahedral cages whereas the two other ligands, with two different approaches of loosened point chirality, lead to a significant breakdown of the diastereoselectivity to generate a mixture of (ΔΔΔΔ and ΛΛΛΛ) isomers. The cages are highly emissive (luminescence quantum yields of 16(1) to 18(1)%) and exhibit impressive circularly polarized luminescence properties (|g |: up to 0.16). With in-depth studies, we present an example that correlates the nonlinear enhancement of the chiroptical response to the nonlinearity dependence on point chirality.
通常认为，超分子组装的可预测立体选择性形成是一个重要但复杂的过程。在这里，我们表明配体的点手性决定性地影响其超分子组装行为。我们设计了三个具有不同点手性的密切相关的手性配体，并观察到它们自组装成铕（Eu）四金属四面体笼。一种配体表现出高度的非对映选择性组装成同手性（ΔΔΔΔ 或 ΛΛΛΛ）Eu 四面体笼，而另外两种配体，通过两种不同的方法放松点手性，导致非对映选择性显著降低，生成（ΔΔΔΔ 和 ΛΛΛΛ）异构体的混合物。这些笼具有高发光性（荧光量子产率为 16(1) 至 18(1)%)，并表现出令人印象深刻的圆偏振发光性质（|g |：高达 0.16）。通过深入研究，我们提出了一个例子，将手性响应的非线性增强与对手性的非线性依赖性联系起来。
