Akine Shigehisa, Nakano Masato, Sakata Yoko, Yano Sachiko
Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan.
Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan.
Chemistry. 2024 Dec 18;30(71):e202403071. doi: 10.1002/chem.202403071. Epub 2024 Nov 13.
We synthesized a planar macrocyclic dinuclear nickel(II) metallohost from the corresponding macrocyclic imine ligand containing two NO chelate coordination sites and an O cation binding site like 18-crown-6 as well as peripheral hexyl groups. Due to the lipophilic nature of the hexyl groups, the metallohost was soluble in less polar media where its interaction with alkali metal ions was enhanced. The binding studies by NMR spectroscopy clearly showed its strong tendency to form multi-layered structures. The metallohost formed 2 : 1 and 1 : 1 (host/guest) complexes with Na with the two-step binding constants of logK=6.6 and logK=3.0. In contrast, its complexation with larger alkali metal ions (K, Rb, Cs) preferentially gave 3 : 2 (host/guest) complexes when 2/3 equiv. of the guest was present. The three-layered structures of these 3 : 2 complexes were well characterized by mass spectrometry and 2D COSY/ROESY experiments as well as DFT calculations, elucidating their unique structural feature with three chemically different environments due to the oppositely curved two [Ni(saloph)] moieties of the metallohost. Therefore, the three-layered structures were preferentially formed when larger alkali metal ions (K, Rb, Cs) were complexed with the metallohost.
我们从相应的大环亚胺配体合成了一种平面大环双核镍（II）金属主体，该配体含有两个NO螯合配位位点、一个类似18-冠-6的O阳离子结合位点以及外围己基。由于己基的亲脂性，该金属主体可溶于极性较小的介质中，在其中它与碱金属离子的相互作用增强。通过核磁共振光谱进行的结合研究清楚地表明其形成多层结构的强烈倾向。该金属主体与Na形成了2∶1和1∶1（主体/客体）配合物，两步结合常数分别为logK = 6.6和logK = 3.0。相比之下，当存在2/3当量的客体时，它与较大的碱金属离子（K、Rb、Cs）的络合优先得到3∶2（主体/客体）配合物。这些3∶2配合物的三层结构通过质谱、二维COSY/ROESY实验以及密度泛函理论计算得到了很好的表征，阐明了由于金属主体中两个[Ni（saloph）]部分相反的弯曲而具有三种化学不同环境的独特结构特征。因此，当较大的碱金属离子（K、Rb、Cs）与金属主体络合时，优先形成三层结构。
