A novel supramolecular assembly has been fabricated by the inclusion complexation between organo-selenium bridged bis(β-cyclodextrin)s 2 and calix[4]arene derivative 3 in water-acetonitrile (1:1) mixture solution and characterized by fluorescence, 2D NMR, TEM, SEM, and STM images, showing the nanometer structural wire-shaped aggregates.

The complex stability constants (KS) and thermodynamic parameters (△G°, △H°, and T△S°) for 1:1 inclusion complexation of β-cyclodextrin (β-CD) derivatives, 6-O-phenyl-β-CD (2) 6-O-(4-formylphenyl)-β-CD (3), 6-O-(4-nitrophenyl)-β-CD (4), 6-O-(4-bromophenyl)-β-CD (5), 6-O-(4-chlorophenyl)]-β-CD (6), and 6-O-(4-hydroxybenzoyl)-β-CD (7) with representative guest molecules, cyclic alcohols (cyclopentanol, cyclohexanol, cycloheptanol, cyclooctanol), (±)-borneol, and (±)-camphor, have been determined by means of titration microcalorimetry in an aqueous phosphate buffer solution (pH=7.20) at 298.15K. The results obtained indicate that the introduction to β-CD of an aromatic ring bearing different substituent groups significantly enhances the molecular binding ability and moderately alters the chiral discrimination ability for the guests examined here, displaying the highest enantioselectivity of up to 4.01 for the inclusion complexation of 6 with (±)-camphor. The enhanced molecular/chiral discrimination ability caused by derivatization is attributed solely to increased positive entropy changes due to the expanding hydrophobic interaction and desolvation effects. The binding modes of host-guest interactions derived from ROESY spectroscopy data show that the resulting complex of 4 and (+)-borneol possesses better induced-fit interaction as compared to (-)-borneol, which is responsible for the enhanced molecular/chiral recognition ability.

A novel supramolecular assembly, bis(molecular tube)s composed of complexes of organoselenium-bridged β-cyclodextrins and platinum(Ⅳ) ion, have been fabricated via the pseudorotaxane with poly(propylene glycol) and characterized by 1H NMR, TEM, and AFM images, etc.

To investigate quantitatively the cooperative binding ability of several β-cyclodextrin oligomers bearing single or multiligated metal center(s), the inclusion complexation behavior of four bis(β-cyclodextrin)s (2-5) linked by 2,2'-bipyridine-4,4'-dicarboxy tethers and their copper(Ⅱ) complexes (6-9) with representative dye guests, i.e., methyl orange (MO), acridine red (AR), rhodamine B (RhB), ammonium 8-anilino-1-naphthalenesulfonic acid (ANS), and sodium 6-(p-toludino)-2-naphthalenesulfonate (TNS), have been examined in aqueous solution at 25°C by means of UVvis, circular dichroism, fluorescence, and 2D NMR spectroscopy. The results obtained indicate that bis(β-cyclodextrin)s 2-5 can associate with one or three copper(Ⅱ) ion(s) producing 2:1 or 2:3 bis-(β-cyclodextrin)-copper(Ⅱ) complexes. These metal-ligated oligo(β-cyclodextrin)s can bind two model substrates to form intramolecular 2:2 host-guest inclusion complexes and thus significantly enhance the original binding abilities of parent β-cyclodextrin and bis(β-cyclodextrin) toward model substrates through the cooperative binding of two guest molecules by four tethered cyclodextrin moieties, as well as the additional binding effect supplied by ligated metal center(s). Host 6 showed the highest enhancement of the stability constant, up to 38.3 times for ANS as compared with parent β-cyclodextrin. The molecular binding mode and stability constant of substrates by bridged bisand oligo(β-cyclodextrin)s 2-9 are discussed from the viewpoint of the size/shape-fit interaction and molecular multiple recognition between host and guest.

A series of novel 6,6'-bis(bcyclodextrin) s linked by 2,2'-bipyridine-4,4'-dicarboxy tethers; that is, 2,2'-bipyridine-4,4'-dicarboxy-bridged bis(6-O-bcyclodextrin) (2) and N,N'-bis(2-aminoethyl)-2,2'-bipyridine-4,4'-dicarboxamide-bridged (3), N,N'-bis(5-amino-3-azapentyl)-2,2'-bipyridine-4,4'-dicarboxamide-bridged (4) and N,N'-bis(8-amino-3,6-diazaoctyl)-2,2'-bipyridine-4,4'-dicarboxamide-bridged bis(6-amino-6-deoxy-b-cyclodextrin) (5), has been synthesized as cooperative multipoint-recognition receptor models. The inclusion complexation behavior of 2-5 with organic dyes; that is, ammonium 8-anilino-1-naphthalenesulfonate, Brilliant Green, Methyl Orange, Acridine Red, and Rhodamine B, has been investigated in aqueous phosphate buffer solutions (pH7.20) at 25℃ by means of ultraviolet, fluorescence, and circular dichroism spectrometry as well as by fluorescence lifetime measurements. The spectral titrations gave the complex stability constants (KS) and Gibbs' free energy changes (△℃) for the inclusion complexation of 2-5 with the organic dyes and other thermodynamic parameters (△H°and △S°) for the inclusion complexation of 2-4 with the fluorescent dyes Acridine Red and Rhodamine B. Bis(b-cyclodextrin)s 2-5 displayed higher binding abilities toward most of the examined dye molecules than native b-cyclodextrin 1; this is discussed from the viewpoints of the size/shape-fit concept, the induced-fit interaction, and cooperative, multipoint recognition by the bridging chain and the dual hydrophobic cavities. Thermodynamically, the inclusion complexation of 2-4 with Acridine Red is totally enthalpy driven with a negative or minor positive entropic contribution, but the inclusion complexation with Rhodamine B is mainly entropy-driven with a mostly positive, but occasionally negative, enthalpic contribution; in some cases this determines the complex stability.