Synthesis of novel bis(beta-cyclodextrin)s and metallobridged bis(beta-cyclodextrin)s with 2,2'-diselenobis(benzoyl) tethers and their molecular multiple recognition with model substrates

To investigate quantitatively the cooperative binding ability of beta-cyclodextrin dimers, a series of bridged bis(beta-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 degrees C to give the complex stability constants (K(S)) and Gibbs free energy changes (-DeltaG degrees ) for the inclusion complexation of hosts 2-9 with organic dyes and other thermodynamic parameters (DeltaH degrees and TDeltaS degrees ) for the inclusion complexation of 2-5with fluorescent dyes ANS and TNS. The results obtained indicate that beta-cyclodextrin dimers 2-5 can coordinate with one or two platinum(IV) ions to form 1:1 or 1:2 stoichiometry metallobridged bis(beta-cyclodextrin)s. As compared with parent beta-cyclodextrin (1) and bis(beta-cyclodextrin)s 2-5, metallobridged bis(beta-cyclodextrin)s 6-9 can further switch the original molecular binding ability through the coordinating metal to orientate two beta-cyclodextrin cavities and an additional binding site upon the inclusion complexation with model substrates, giving the enhanced binding constants K(S) 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 beta-cyclodextrins. The Gibbs free energy change (-DeltaG degrees ) 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 (-DeltaH degrees ) by the cooperative binding of one guest molecule in the closely located two beta-cyclodextrin cavities as compared with parent beta-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.     

37-冠-10的合成及离子选择性

以均苯四甲酸二酰亚胺和1,5-萘二酚为基本结构单元,设计合成了一种不对称的37-冠-10 (1), 解析了其晶体结构,进而采用紫外和核磁等手段研究了其与一些阳离子的键合行为. 结果表明,冠醚1存在分子内的电荷转移相互作用,导致的较小空腔对锂离子表现出较强的键合能力.     

钾离子调控的1,5-萘基桥联双冠醚的"off-on-off"和"on-off-on"行为

报道了萘基桥联双苯并15-冠-5的合成,研究了K+调控的双冠醚自组装过程以及伴随的独特荧光行为.这种发光行为不仅可以模拟一个荧光"off-on-off"开关和一个荧光"on-off-on"开关,而且其组装模式和功能上类似于酶的二聚化过程.     

A heterowheel [3]pseudorotaxane by integrating β-cyclodextrin and cucurbit[8]uril inclusion complexes

A heterowheel [3]pseudorotaxane was prepared by integrating two binary inclusion complexes of β-cyclodextrin-hydroxynaphthalene (β-CD·3) with a cucurbit[8]uril-viologen derivative (CB[8]·2), in which simultaneous molecular recognition of the adamantine moiety in 2 by β-CD and the charge-transfer interaction of 3 with the viologen nucleus of 2 in the cavity of CB[8] are two crucial factors for the formation of the quaternary complex.     

The structure and thermodynamics of calix[n]arene complexes with dipyridines and phenanthroline in aqueous solution studied by microcalorimetry and NMR spectroscopy

The complex stability constants (K(S)) and thermodynamic parameters (DeltaH degrees and TDeltaS degrees) for 1:1 intermolecular complexation of three water-soluble calixarenes, that is, p-sulfonato calix[4]arene (C4AS), p-sulfonato thiacalix[4]arene (TCAS), and p-sulfonato calix[5]arene (C5AS), with dipyridines (4-DPD and 2-DPD) and 1,10-phenanthroline (Phen) have been determined by means of titration microcalorimetry in an acidic buffer solution (pH = 2.0) at 298.15 K, and their binding modes have been investigated by (1)H NMR and 2D ROESY NMR spectroscopy. The results obtained indicate that 4-DPD, 2-DPD, and Phen are included in the cavity of C5AS with the different patterns, this is, accumbent for 4-DPD, acclivitous for 2-DPD and Phen, while Phen is included upright in the cavity of C4AS. The K(S) values decrease with increasing cavity size of host molecules but enhance with extending conjugation degree of guest molecules, and thus C4AS exhibits an exceptionally high Phen/4-DPD selectivity of 22.5. Thermodynamically, the complexation of DPDs/Phen with the water-soluble calixarenes is obviously enthalpy-driven, but the molecular selectivity is mainly governed by the entropy term.     

Preparation and characterization of inclusion complexes of topotecan with sulfonatocalixarene

Inclusion complex of sulfonatocalix[4]arene (SC4A) with topotecan (TPT) was prepared, and its inclusion complexation behaviors, such as stoichiometry, complex stability constants, and inclusion mode, were investigated by means of UV/Vis spectroscopy, DSC, and 2D NMR. The obtained results show that the quinoline ring and the dimethylaminomethyl group of TPT can be efficiently encapsulated in SC4A, and the complex is more soluble than free TPT.     

Recognition-induced supramolecular porous nanosphere formation from cyclodextrin conjugated by cholic acid

A supramolecular porous nanosphere is constructed from amphiphilic cholic acid-modified cyclodextrin triggered by guest sodium 1-naphthylamino-4-sulfonate and is comprehensively characterized by nuclear magnetic resonance (NMR), light scattering, transmission electron microscopy, and gas adsorption experiments. The results obtained show that the porous nanosphere with the radius of 25-35 nm has moderate nitrogen adsorption ability. Further NMR, circular dichroism, and the fluorimetric titrations on the self-assembling behavior in aqueous solution reveal that the substituting group of the guest molecule and pH values are the key to induce the formation of the porous nanosphere.     

Selective binding and inverse fluorescent behavior of magnesium ion by podand possessing plural imidazo[4,5-f]-1,10-phenanthroline groups and its Ru(II) complex

[structure: see text] Two podands, 4,4'-[(ethylenedioxy)bis(ethyleneoxy)]bis[1-(2-imidazo[4,5-f]-1,10-phenanthroline)benzene] (1) and [Ru(phen)(2)](2)(1)(PF(6))(4) (2) complex, were synthesized from 1,10-phenanthroline. The photophysical behavior and the binding ability of 1 and 2 with some alkali metal and alkaline earth cations were investigated by UV-vis and fluorescence spectrometry and (1)H NMR experiments as well as fluorescence lifetime measurements. The complex stability constants (K(S)) and Gibbs free energy changes (DeltaG degrees ) for the stoichiometric 1:1 complexation of 1 and 2 with the cations were obtained by the fluorimetric titrations. The podands 1 and 2 exhibit different fluorescent behavior in the cations examined, i.e., fluorescence quenching for 1, and fluorescence enhancement for 2. In particular, 1 showed responses specific for Mg(2+), resulting in readily distinguishable by eye.     

Synthesis of Double-Armed Benzo-15-crown-5 and Their Complexation Thermodynamics with Alkali Cations

A series of double-armed benzo-15-crown-5 lariats (3–8) have been synthesized by the reaction of 4′, 5′-bis(bromomethyl)-benzo-15-crown-5 (2) with 4-hydroxybenzaldehyde, phenol, 4-chlorophenol, 4-methoxyphenol, 2-hydroxybenzaldehyde, and 4-acetamidophenol in 43 ~ 82% yields, respectively. The complex stability constants (K _S) and thermodynamic parameters for the stoichiometric 1:1 and/or 1:2 complexes of benzo-15-crown-5 1 and double-armed crown ethers 3–8 with alkali cations (Na⁺, K⁺, Rb⁺) have been determined in methanol–water (V/V=8:2) at 25 °C by means of microcalorimetric titrations. As compared with the parent benzo-15-crown-5 1, double-armed crown ethers 3–8 show unremarkable changes in the complex stability constants upon complexation with Na⁺, but present significantly enhanced binding ability toward cations larger than the crown cavity by the secondly sandwich complexation. Thermodynamically, the sandwich complexations of crown ethers 3-8 with cations are mostly enthalpy-driven processes accompanied with a moderate entropy loss. The binding ability and selectivity of cations by the double-armed crown ethers are discussed from the viewpoints of the electron density, additional binding site, softness, spatial arrangement, and especially the cooperative binding of two crown ether molecules toward one metal ion.Graphical Abstract Synthesis of Double-Armed Benzo-15-crown-5 and Their Complexation Thermodynamics with Alkali CationsYU LIU*, JIAN-RONG HAN, ZHONG-YU DUAN and HENG-YI ZHANG This revised version was published online in July 2005 with a corrected issue number.