Design and Optimization of Molecular Nanovalves Based on Redox-Switchable Bistable Rotaxanes

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• 作者：Thoi D. Nguyen ; Yi Liu ; Sourav Saha ; Ken C.-F. Leung ; J. Fraser Stoddart ; Jeffrey I. Zink
• 刊名：Journal of the American Chemical Society
• 出版年：2007
• 出版时间：January 24, 2007
• 年：2007
• 卷：129
• 期：3
• 页码：626 - 634
• 全文大小：387K
• 年卷期：v.129,no.3(January 24, 2007)
• ISSN：1520-5126

文摘

Redox-controllable molecular nanovalves based on mesoporous silica nanoparticles have beenfabricated, using two bistable [2]rotaxanes with different spacer lengths between their recognition sites asthe gatekeepers. Three different linkers with varying chain lengths have been employed to attach the bistable[2]rotaxane molecules covalently to the silica substrate. These nanovalves can be classified as having INor OUT locations, based on the positions of the tethered bistable [2]rotaxanes with respect to the entrancesto the nanopores. The nanovalves are more efficient when the bistable [2]rotaxane-based gatekeepersare anchored deep within (IN) the pores than when they are attached closer to (OUT) the pores' orifices.The silica nanopores can be closed and opened by moving the mechanically interlocked ring componentof the bistable [2]rotaxane closer to and away from the pores' orifices, respectively, a process which allowsluminescent probe molecules, such as coumarins, tris(2-phenylpyridine)iridium, and rhodamine B, to beloaded into or released from the mesoporous silica substrate on demand. The lengths of the linkers betweenthe surface and the rotaxane molecules also play a critical role in determining the effectiveness of thenanovalves. The shorter the linkers, the less leaky are the nanovalves. However, the distance betweenthe recognition units on the rod section of the rotaxane molecules does not have any significant influenceon the nanovalves' leakiness. The controlled release of the probe molecules was investigated by measuringtheir luminescence intensities in response to ascorbic acid, which induces the ring's movement away fromthe pores' orifices, and consequently opens the nanovalves.