香豆素基金属-有机笼对氨基葡萄糖的识别

Metal–organic octahedron for selective recognition of glucosamine

摘要:

将发光性质优异的香豆素基团作为荧光信号单元引入有机配体H3L，与过渡金属锌离子配位自组装，构建了一例金属-有机八面体笼状化合物Zn-L，利用主客体氢键弱作用实现了对氨基葡萄糖的选择性识别。高分辨质谱和紫外可见吸收光谱结果显示金属-有机笼状化合物为M6L4的八面体构型，十二个香豆素基团均匀分布在八面体笼状结构的顶点，该结构在溶液中具有良好的稳定性，带有窗口的空腔允许尺寸合适的客体分子自由进出。主客体核磁滴定显示氨基葡萄糖通过多重氢键作用与笼状结构相结合，高分辨质谱测试表明笼状结构与氨基葡萄糖形成了化学计量比为1:2的主客体包合物，荧光滴定光谱拟合显示络合常数为1.6 * 108 M–2，证实主客体间具有较强的络合作用，有利于笼状结构对氨基葡萄糖的选择性识别。氨基葡萄糖分子对其荧光强度淬灭高达93%，而其他9种常见生物糖类小分子只能淬灭5~20%，显示出了八面体笼对氨基葡萄糖分子的选择性荧光响应。

Abstract:

By introducing the coumarin with excellent photophysical properties into the backbone of ligand H3L as a fluorescent signal unit, a new metal-organic octahedral cage Zn?L was prepared by coordinating with transition metal ion Zn(Ⅱ) for realizing selective recognition of glucosamine via the host-guest hydrogen bonding interaction. The characterization results of high-resolution mass spectroscopy and ultraviolet-visible spectroscopy show that this metal-organic cage compound has a M6L4 octahedral structure. Twelve coumarin groups are uniformly distributed at the vertical positions of the octahedral cage, which has high stability in solution and possesses a large cavity with the opening windows that allows free ingress and egress of the guest molecules with suitable size. 1H NMR titration shows that glucosamine combine with cage structure through multiple hydrogen bonding. High resolution mass spectrometry test suggests that a stoichiometric ratio of 1:2 host-guest inclusion complex is formed between the metal-organic octahedral cage Zn?L and the glucosamine and fluorescence titration spectra fitting shows an association constant 1.6 ? 108 M–2, confirming the strong complexation between host and guest, which is conducive to the selective recognition of glucosamine by the cage structure. Glucosamine molecule quenches the fluorescence intensity of Zn?L by up to 93%, while other 9 common biological carbohydrate molecules can only quench 5-20%, showing a highly selective fluorescence response of Zn?L to glucosamine molecule