Morie Masayuki, Sekiya Ryo, Haino Takeharu
Department of Chemistry, Graduate School of Advanced Science and Engineering, Hiroshima University, 1-3-1 Kagamiyama, HigashiHiroshima, Hiroshima, 739-8526, Japan.
Chem Asian J. 2021 Jan 4;16(1):49-55. doi: 10.1002/asia.202001154. Epub 2020 Nov 17.
The title complex is a triple-stranded metallohelicate organized by the self-assembly of 5,17-difunctionalized calix[4]arenes and metal cations with octahedral coordination geometry. Due to hydrophilic triethylene glycol chains on the lower rim of the calix[4]arene, the metallohelicate can encapsulate cationic guests in water. NMR and UV-vis titration experiments reveal that the metallohelicate captures a pyridinium guest with an alanine derivative to form a host-guest complex with a host-guest ratio of 1 : 1. CD spectroscopy confirms the bias of the P- and M-helical sense of the metallohelicate by the captured guest. The metallohelicate captures two molecules of dicationic N,N'-dimethyl-DABCO and monocationic N-methyl quinuclidine, exhibiting a positive allosteric effect. H NMR titration experiments indicate that the bound guests are in close proximately to the aromatic rings of the ligands. Molecular mechanics calculations based on the UV-vis and NMR observations suggest that the first guest preorganizes the conformation of the metallohelicate to facilitate access of the second guest to the cavity.
标题配合物是一种三链金属螺旋体，由5,17 - 二官能化杯[4]芳烃和具有八面体配位几何结构的金属阳离子自组装而成。由于杯[4]芳烃下缘的亲水性三甘醇链，该金属螺旋体能够在水中包封阳离子客体。核磁共振（NMR）和紫外可见（UV-vis）滴定实验表明，该金属螺旋体与带有丙氨酸衍生物的吡啶鎓客体形成主客体比为1∶1的主客体配合物。圆二色（CD）光谱证实了被捕获客体对金属螺旋体P - 螺旋和M - 螺旋方向的偏向性。该金属螺旋体捕获了两分子的双阳离子N,N'-二甲基 - 1,4 - 二氮杂双环[2.2.2]辛烷和单阳离子N - 甲基奎宁环，表现出正变构效应。核磁共振氢谱（¹H NMR）滴定实验表明，结合的客体与配体的芳香环紧密相邻。基于紫外可见光谱和核磁共振观察结果的分子力学计算表明，第一个客体使金属螺旋体的构象预组织化，从而便于第二个客体进入空腔。
