A tong-like fluorescence sensor for metal ions: perfect conformational switch of hinge sugar by pyrene stacking
作者:Hideya Yuasa、Naofusa Miyagawa、Masatoshi Nakatani、Masayuki Izumi、Hironobu Hashimoto
DOI:10.1039/b411344f
日期:——
Carbohydrates are among the potential materials for molecular devices, since they are abundant natural resources. However, their rigidity has restricted their use for movable devices. Hinge sugars, 2,4-diamino-2,4-dideoxy-xylopyranosides, shed light on the use of carbohydrates as movable components, as demonstrated by the motion by which all four equatorial substituents can change to an axial orientation in synchronization with a chelation-driven 4C1–1C4 ring flip. In this study, we synthesized a tong-like metal ion sensor, 1,3-di-O-pyrenylmethylated hinge sugar (1), and its model compound, methyl 2,4-di-O-pyrenecarbonyl-xylopyranoside (2), to extend the abilities of hinge sugars as molecular components. From observations of the solvent-dependent conformational and fluorescent behavior of 2, we found that the pyrene stacking assists the 1C4 formation of xylopyranoside by 1.7 kcal mol−1. We also found that compound 1 produced excimer fluorescence by chelation to Pt2+, Zn2+, Cd2+, Mg2+ or Mn2+, and unexpectedly by addition of acids. 1H NMR measurements ascribed this behavior to the 4C1–1C4 ring flip of hinge sugar in response to chelation or protonation at N2, and revealed rapid and perfect 1C4 formation in the case of Zn2+. These findings will extend the scope of hinge sugars as movable components.
碳水化合物是分子装置的潜在材料之一,因为它们是丰富的自然资源。然而,它们的刚性限制了其在可移动装置中的应用。铰链糖--2,4-二氨基-2,4-二脱氧-吡喃木糖苷--揭示了碳水化合物作为可移动元件的用途,其四个赤道取代基可以随着螯合作用驱动的 4C1-1C4 环翻转而同步改变为轴向。在这项研究中,我们合成了一种类似铗子的金属离子传感器--1,3-二-O-芘甲基化铰链糖(1)及其模型化合物--甲基 2,4-二-O-芘羰基吡喃糖苷(2),以扩展铰链糖作为分子元件的能力。通过观察 2 的溶剂依赖性构象和荧光行为,我们发现芘堆叠有助于木吡喃糖苷 1C4 的形成,提高了 1.7 kcal mol-1。我们还发现,化合物 1 在与 Pt2+、Zn2+、Cd2+、Mg2+ 或 Mn2+ 螯合时会产生准分子荧光,而在加入酸后则会产生意想不到的荧光。1H NMR 测量将这种行为归因于铰链糖在 N2 处的螯合或质子化作用下的 4C1-1C4 环翻转,并发现在 Zn2+ 的情况下,1C4 迅速而完美地形成。这些发现将扩大铰链糖作为可移动成分的范围。