Bis(polypseudorotaxane)s possessing the bridged bis(β-cyclodextrin)s with multi coordinated metal centers are prepared, in which β-cyclodextrin (β-CD) acts as the host structure, amino-terminated polypropylene glycol(PPG; MW=2000) as the guest, and nickel(II) complexes as templating moieties. The assembly behavior is comprehensively studied by NMR spectroscopy, gel permeation chromatography(GPC), end group assay, static light scattering, thermogravimetric(tG), differential thermal analysis(dTA), and scanning tunneling microscopy(STM). The obtained results indicate that not only could the two PPG molecules be respectively threaded into metallo-bridged bis(β-CD)s forming the double-strand structure, but they also could play a stabilizing role in the molecular aggregation. The fluorescence titrations are performed in a mixture of acetonitrile/water to calculate the effective binding constants and thermodynamic parameters for the threading process of 2 onto PPG. The results reveal that the assembly process as being driven by favorable entropic contributions accompanying a large positive enthalpic change. The present investigations provide a simple way to prepare multicomponent nanometer-scale organic supermolecules with multiple CD dimers coordinated metal centers.

采用荧光光谱滴定的方法测定了一系列联喹啉桥联双环糊精在磷酸缓冲溶液中(25℃，pH＝7.2)与几种染料客体分子形成化学计量比为1∶1的超分子配合物的稳定常数。结果表明，拥有刚性和大π电子体系的联喹啉桥联双环糊精比相应的联吡啶桥联双环糊精对三角形的RhB分子和线形的AR分子具有更强的分子键合能力。二维核磁的研究证实，桥联双环糊精对客体分子强的键合能力起源于在一个分子内两个环糊精单元的协同键合。桥联双环糊精对染料客体分子的选择键合能力从主-客体间的尺寸/形状匹配以及几种弱相互作用力的协同效应进行了讨论。

A series of bridged β-cyclo- dextrin(β-CyD) dimers possessing functional tethers of various lengths was synthesized in moderate yield by the treatment of 2,2’-biquinoline- 4,4’-dicarboxylic dichloride with β-CyD or mono[6-oligo(ethylenediamino)-6- deoxy]-β-CyDs. The products were 2,2’-biquinoline-4,4’-dicarboxy-bridged bis(6-O-β-CyD)(8), N,N’-bis(2-amino- ethyl)-2,2’-biquinoline-4,4’-dicarbox- amide-bridged bis(6-amino-6-deoxy-β- CyD)(9), and N,N’-bis(5-amino-3-aza- pentyl)-2,2’-biquinoline-4,4’-dicarbox- amide-bridged bis(6-amino-6-deoxy-β- CyD)(10). The reaction of 8-10 with copper perchlorate give their copper(II) complexes 11-13 in satisfactory yields of over 77%. All the bis(β-CyD)s 8-13 act as efficient fluorescent sensors and display remarkable fluorescence enhancement upon addition of optically inert steroids. The inclusion complexa- tion behaviors of 8-13 when treated with the representative steroids cholate(14), deoxycholate(15), and glycocho- late(16) in aqueous solution at 25℃ were investigated by means of UV/Vis spectroscopy, conductivity and fluorescence measurements, circular dichroism spectroscopy, and 2D NMR spectroscopy. The tether length of bis(β-CyD) 9 allows it to adopt a cooperative host-tether-guest binding mode in which the spacer and guest are co-included in the two CyD cavities. As a result of this cooperation, 9 has a stability constant[Ks] about 2×102 times higher than that of monomodified β-CyD 4 for inclusion complexation with cholate. Metallooligo(β-CyD)s with four β- CyD units have enhanced binding abilities compared with monomodified β-CyDs. These metallo compounds have binding affinities for guest steroids that are up to 50-4.1 ×103 times higher than those of CyDs 2-4. The guest-induced fluorescence enhancement of bis(CyD)s opens a new channel for the design of sensor materials. The complex stability constants of these compounds are discussed from the viewpoint of induced-fit interaction and cooperative multiple binding between host and guest.

Linear biscatechols and triangular triscatechols possessing spacers containing phosphane oxide were synthesized. For this, the central phosphorus was introduced by the reaction of active organometallic intermediates with either dichlorophenylphosphane or phosphorus trichloride/phosphoryl chloride. In the final steps, the methyl ethers at the veratrol units were cleaved by boron tribromide to afford the free phosphane oxide catechol derivatives, which in metal-directed self-assembly processes would lead to helical or tetrahedral supramolecular aggregates.

To investigate quantitatively the cooperative binding ability of β-cyclodextrin dimers, a series of bridged bis(β-cyclodextrin)s with 2,2′-diselenobis(benzoyl) spacer connected by different lengths of oligo(ethylenediamine)s(2-5) and their platinum(IV) complexes(6-9) have been synthesized and their inclusion complexation behavior with selected substrates, such as Acridine Red, Neutral Red, Brilliant Green, Rhodamine B, ammonium 8-anilino-1-naphthalenesulfonate, and 6-p-toluidino-2- naphthalenesulfonic acid, were investigated by means of ultraviolet, fluorescence, fluorescence lifetime, circular dichroism, and 2D-NMR spectroscopy. The spectral titrations have been performed in aqueous phosphate buffer solution(pH 7.20) at 25°C to give the complex stability constants(KS) and Gibbs free energy changes(-ΔG°) for the inclusion complexation of hosts 2-9 with organic dyes and other thermodynamic parameters(ΔH° and TΔS°) for the inclusion complexation of 2-5 with fluorescent dyes ANS and TNS. The results obtained indicate that β-cyclodextrin dimers 2-5 can coordinate with one or two platinum(IV) ions to form 1:1 or 1:2 stoichiometry metallobridged bis(β-cyclodextrin)s. As compared with parent β-cyclodextrin(1) and bis(β-cyclodextrin)s 2-5, metallobridged bis(β-cyclodextrin)s 6-9 can further switch the original molecular binding ability through the coordinating metal to orientate two β-cyclodextrin cavities and an additional binding site upon the inclusion complexation with model substrates, giving the enhanced binding constants KS for both ANS and TNS. The tether length between two cyclodextrin units plays a crucial role in the molecular recognition with guest dyes. The binding constants for TNS decrease linearly with an increase in the tether length of dimeric β-cyclodextrins. The Gibbs free energy change(-ΔG°) for the unit increment per ethylene is 0.32 kJ mol 1 for TNS. Thermodynamically, the higher complex stabilities of both ANS and TNS upon the inclusion complexation with 2-5 are mainly contributed to the favorable enthalpic gain(-ΔH°) by the cooperative binding of one guest molecule in the closely located two β-cyclodextrin cavities as compared with parent β-cyclodextrin. The molecular binding ability and selectivity of organic dyes by hosts 1-9 are discussed from the viewpoints of the multiple recognition mechanism and the size/shape-fitting relationship between host and guest.