Strategic Exploration of Quinoline-Based Materials

我们设计并合成了四喹啉（TEQ），这是一种包含四个向内取向氮原子的新型共轭大环，具有刚性鞍形结构和特殊的化学和物理性质。TEQ是由喹啉酰胺底物和炔环二聚体在Tf2O和吡啶衍生物存在下合成的。进行DFT计算是为了更深入地了解反应机理。c2对称取代的TEQ具有相当高的翻转能垒以确保其手性，实验证实，即使在240°C下也没有对映体过量的侵蚀。TEQ可容纳各种类型的过渡金属阳离子，如Fe2+、Co2+、Ni2+、Cu2+、Zn2+和Pd2+，形成相应的金属配合物，对阳离子交换和质子化具有较高的动力学稳定性。这些配合物的结构无疑是由x射线晶体学证实的，并且TEQ-Fe（II）配合物在催化剂负载低至0.1 mol%的脱氢反应中表现出催化活性。TEQ显示出固有的弱荧光，在质子化或质子化或Zn（II）阳离子的加入时变得强烈发射，这表明它有可能作为结构坚固的pH或Zn探针。

We have designed and synthesized TEtraQuinoline (TEQ), a new family of conjugated macrocycles containing four inwardly oriented nitrogen atoms, which exhibit a rigid saddle-shape structure and special chemical and physical properties. TEQ is synthesized from a cyclic dimer of quinoline-amide substrate and an alkyne in the presence of Tf2O and pyridine derivatives. DFT calculations are carried out to gain a deeper understanding of the reaction mechanism.The C2-symmetric substituted TEQ has a considerably high energy barrier for flipping to secure its chirality, which has been experimentally confirmed by no erosion of the enantiomeric excess even at 240 °C. TEQ accommodates various types of transition metal cations, such as Fe2+, Co2+, Ni2+, Cu2+, Zn2+ and Pd2+, to form corresponding metal complexes, which displayed high kinetic stability toward cation exchange and protonation. The structure of these complexes are undoubtedly confirmed by X-ray crystallography, and a TEQ-Fe(II) complex exhibits catalytic activity in dehydrogenation reactions with catalyst loadings as low as 0.1 mol%. TEQ shows inherently weak fluorescence, and it becomes strongly emissive upon protonation or addition of upon protonation or addition of Zn(II) cations, suggesting potential application as structurally robust pH or Zn probes.