以籠狀冠醚分子為基本架構的離子感測器 與分子機械之研究

Abstract

我們成功地合成了一個新型的籠狀冠醚分子，並利用其與DMDAP在腈甲烷中所產生眾多的 [C–H…O] 作用力來構築一個非常穩定的超分子錯合物 。由於主客間的結合常數甚大，此一籠狀冠醚分子即使在10-5 M的低濃度下，仍然對於DMDAP的螢光有相當大的消光效果。而此溶液在加入Li+、Na+、K+、Mg2+和Ca2+等離子時，藉由離子與冠醚部分的結合可導致DMDAP與籠狀冠醚分子解離進而增強溶液的螢光，而其中Ca2+離子時所產生的螢光增強效果遠大於其他離子。因此，籠狀冠醚分子和DMDAP的錯合系統便成為一個在低濃度溶液中對於Ca2+離子具有良好選擇性的一個主–客超分子化學感測器。

透過良好的結構分析及客體選擇，我們成功地達到利用不同的桿狀分子來選擇性地穿透籠狀冠醚分子不同尺寸面向的開口端並形成其相對的 [2]準車輪烷錯合物的目標。利用順序加入鉀離子和 [2,2,2]cryptand於籠狀冠醚分子與二不同客體的混合溶液中，可選擇性地連續控制不同桿狀分子形成穿透籠狀冠醚分子不同面向開口端的 [2]準車輪烷結構的錯合物。我們亦成功地合成具有四突出取代基的小環分子並以之與籠狀冠醚分子錯合形成獨特的類”烏龜”形的超分子錯合體。

Herein, we report a crown ether based molecular cage that forms extremely stable supramolecular complexes with dimethyldiazapyrenium (DMDAP) ions in CD3CN through the collaboration of multiple weak [C–H…O] hydrogen bonds. The very strong binding affinity in this host–guest system allows the molecular cage to bleach the fluorescence signal of DMDAP substantially in equimolar solutions at concentrations as low as 10-5 M. Remarkably, a 10-5 M equimolar solution of the molecular cage and DMDAP is highly selective toward Ca2+ ions—relative to other biologically important Li+, Na+, K+, and Mg2+ ions—and causes a substantial increase in the fluorescence intensity of the solution. As a result, this molecular cage/DMDAP complex behaves as a supramolecular fluorescence probe for the detection of Ca2+ ions in solution.

We have demonstrated that two different types of thread component (based on a bispyridinium ion and quinone) can be applied to molecular cage to generate different [2]pseudorotaxane-like complexes with precise facial control. A mixture of the two threading components and molecular cage in solution undergoes a newtype of molecular motion, powered through the addition and removal of K+ ions and [2,2,2]cryptand units, in which the rodlike components penetrate the molecular cage alternately through its different faces. In addition, the four-armed macrocyclic guest forms a complex with molecular cage, in which each of the limbs of the guest protrudes from a unique macrocyclic face of the host to result in a turtlelike supramolecular complex.