| Summary: | 博士 === 國立臺灣大學 === 化學研究所 === 94 === 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.
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