Interconnective Host-Guest Complexation of -Cyclodextrin-Calix[4]arene Couples
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- 作者：Jü ; rgen Bü ; gler ; Nico A. J. M. Sommerdijk ; Antonie J. W. G. Visser ; Arie van Hoek ; Roeland J. M. Nolte ; Johan F. J. Engbersen ; and David N. Reinhoudt
- 刊名：Journal of the American Chemical Society
- 出版年：1999
- 出版时间：January 13, 1999
- 年：1999
- 卷：121
- 期：1
- 页码：28 - 33
- 全文大小：123K
- 年卷期：v.121,no.1(January 13, 1999)
- ISSN：1520-5126
文摘
The two G SRC="/images/gifchars/beta2.gif" BORDER=0 ALIGN="middle">-cyclodextrin-calix[4]arene couples 1 and 2 were prepared as sensing molecules for thedetection of organic analytes in water. Compounds 1 and 2 are amphiphilic in nature and form aggregates inaqueous solution. Compound 1 forms vesicles both in the absence and in the presence of guest species, andits fluorescence intensity does not change. Compound 2 forms fibers, which change into vesicles upon guestaddition. This behavior is accompanied by a reduction in fluorescence intensity. The aggregates were visualizedby transmission electron microscopy using both the freeze fracture technique and the uranyl staining method.Langmuir monolayer experiments show that intermolecular interactions lead to a preorganization of 2, whereasmolecules of 1 behave independently analogous to conventional amphiphiles. Fluorescence anisotropy decaymeasurements give evidence for rapid internal dye motion in the aggregates of both compounds 1 and 2. Inaddition, a slower decay process of low amplitude is observed for both compounds, indicating free rotationalmotion of single molecules of 1 but the absence of rotational motion of individual molecules within theaggregates of 2. This difference indicates the intermolecular complexation of the fluorophores in the aggregatesof 2. The fluorescence lifetimes of aqueous solutions of 2 reveal that the reduction in fluorescence intensityis based on static quenching by the amino group present in the spacer of 2. Our results show the presence ofvesicular bilayers of independent amphiphiles for 1, and for 2 the formation of assemblies of molecular threadswhich are composed by interconnective, linear host-guest complexation.