Two β-cyclodextrin derivatives bearing appended quinolyl and isoquinolyl arms,i.e.mono-（6-quinolyl- 6-deoxy）-β-cyclodextrin（1） and mono-（6-isoquinolyl-6-deoxy）-β-cyclodextrin（2） were synthesized in satisfactory yields and fully characterized.Their original conformations and binding behaviors toward four bile salt guests,that is,sodium cholate（CA）,sodium deoxycholate（DCA）,sodium glycocholate （GCA）,and sodium taurocholate（TCA）,were investigated by means of fluorescence,circular dichroism and 2D NMR spectroscopy.The study of solution structures revealed that both quinolyl and isoquinolyl arms were located outside the cyclodextrin cavity.The results obtained from the fluorescence titrations showed that the binding abilities of hosts 1 and 2 with selected bile salts varied in an order of DCA 〉 CA 〉 GCA.The selective binding of hosts toward bile salt guests was discussed from the viewpoints of induced-fit and multiple binding.
A n-conjugated phenylaza-15-crown-5-triazol-substituted coumarin fluoroionophore 1 was synthesized by cop- per（I）-catalyzed Huisgen alkyne-azide 1,3-dipolar cycloaddition （CuAAC ＂click＂ reaction）. 1 can display selective fluorescence enhancement toward Fe3＋ over Hg2＋, Cr3＋ and the other metal ions in aqueous solution. In sharp con- trast, the fluorescence behavior between Fe3＋ and Hg2＋ is completely reversed in EtOH. That is, Hg2＋ gives the largest fluorescence enhancement over Cr3＋, Fe3＋ and the other metal ions.
A twin-axial hetero[5]pseudorotaxane was constructed based on 1-hexyl-4,40-bipyridinium guest 1 and cucurbit[8]uril（CB[8]）and a-cyclodextrin（a-CD）.In its structure,CB[8]included two bipyridinium units to realize the twin-axial mode,and the hexyl chain was threaded into the cavity of a-CD.The[5]pseudorotaxane contains two types of macrocyclic hosts while the single axial and twin axial modes co-exist in its structure.The transformation of[5]pseudorotaxane could be realized by the addition of acid and 2,6-dihydroxynaphthalene（HN）.
Li-Hua WangZhi-Jun ZhangHeng-Yi ZhangHai-Lang WuYu Liu
A [3]rotaxane I involving two naphtho-21-crown-7 （N21 C7） rings and a dumbbell-shaped component 4 was synthesized. The dumbbell-shape molecule 4 contains one viologen nucleus, two secondary alkyl ammonium sites and two phenyl stoppers. After threading the N21C7 ring with the thread-like ammonium guest 3, the copper（l）-catalyzed Huisgen alkyne-azide 1,3-dipolar cycloaddition （CuAAC ＂click＂ reaction）, was performed to connect the pseudorotaxanes with viologen unit 2 and generate 1. Through treating the [3]rotaxane by the base and acid circularly, the two N21 C7 rings can make shuttling motion along the axle. Meanwhile the distance between the electron-deficient viologen unit and the electron-rich naphthol group can be adjusted precisely along with a remarkable intramolecular charge- transfer （CT） behavior.
