Abstract

Abstract

Abstract

Abstract

Interaction of cyclodextrins (CDs) with an alternating copolymer of sodium maleate and dodecyl vinyl ether (pC₁₂MA), which forms micelle-like aggregates in aqueous media, is investigated by several NMR techniques to explore the competition of the complexation of CDs with the dodecyl (C₁₂) groups and the self-association of the C₁₂ groups. ¹H NMR and two-dimensional nuclear Overhauser effect spectroscopy data demonstrate that α-CD interacts significantly with the C₁₂ groups in pC₁₂MA but β- or γ-CD does not, which indicates that the competition with self-association of the C₁₂ groups enhances the selectivity towards α-CD. Furthermore, the binding isotherm prepared using ¹H NMR data exhibits a sigmoidal curve, which is indicative of cooperative complexation of α-CD with pC₁₂MA.

Rückgrat unnötig: Aus einem gastmodifizierten Cyclodextrin (CD) ohne Polymerrückgrat wurde ein supramolekulares Hydrogel synthetisiert. Das β-CD bildet als Folge von Wirt-Gast-Wechselwirkungen supramolekulare Fibrillen, und Wasserstoffbrücken zwischen den CDs vernetzen die Fibrillen zum Hydrogel. Gel-Sol-Übergänge werden durch Zugabe eines weiteren Gasts oder eines Denaturierungsagens ausgelöst (siehe Beispiel).

No backbone required: A supramolecular hydrogel has been synthesized from a guest-modified cyclodextrin (CD) without a polymer backbone. The β-CD forms supramolecular fibrils through host–guest interactions, and then hydrogen bonds between the CDs cross-link the fibrils to give a hydrogel. Gel-to-sol transitions can be effected by adding a competitive guest or a denaturing reagent (see example).

New [2]- and [3]pseudorotaxanes containing α-cyclodextrin (α-CDs) molecules as rotors and alkyl pyridinium derivatives as axles were prepared by a slipping process. The inclusion behavior of these rotaxanes was investigated by using one- and two-dimensional NMR spectroscopy. The methyl group at the 2-position of the pyridinium moiety at the end of each axle molecule was found to control the rates of threading of the α-CD onto the axle molecules. α-CD can approach axle molecules from a particular direction to form inclusion complexes. Axle molecules that contain a 2-methylpyridinium moiety at one end and a bulky stopper at the other end can regulate the direction of approach to give a [2]pseudorotaxane such as 2 b–α-CD. A [3]pseudorotaxane in which two α-CD molecules are arranged facing in the same direction at two stations of the tetracationic axle molecule was also obtained. These face-selective behaviors are dominated by kinetic processes rather than thermodynamic processes.

Summary: We have successfully constructed a redox-responsible hydrogel system by combination of β-cyclodextrin (β-CD), dodecyl-modified poly(acrylic acid) [p(AA/C₁₂)], and a redox-responsive guest, ferrocenecarboxylic acid (FCA). In the reduced state of FCA, the ternary mixture exhibited a gel-like behavior, whereas, in its oxidized state, the mixture exhibited a sol behavior.

A bit on the side: A side-chain polyrotaxane that consists of simple components is successfully constructed and controlled by using photoisomerization of an azobenzene moiety at the terminal of the side chain.

Two types of supramolecular polymers based on cyclodextrins were prepared. One was a host–guest type, and the other was a polyrotaxane type. When a guest part was covalently attached to cyclodextrin, they formed supramolecular dimers, a cyclic daisy chain, supramolecular oligomers, and polymers. t-Boc-cinnamamide-α-cyclodextrin was found to form chiral supramolecular polymers in aqueous solutions. Supramolecular poly[2]rotaxane polymers and supramolecular α,β-cyclodextrin copolymers were obtained. Polyrotaxanes containing β-cyclodextrin or γ-cyclodextrin were prepared. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5113–5119, 2006

Summary: By utilizing the interaction of α-cyclodextrin (α-CD) with dodecyl side chains in polymers of x mol-% dodecyl-modified poly(acrylic acid) (p(AA/C₁₂(x))), systems that undergo gel-to-sol and sol-to-gel transitions were successfully constructed. Rheological experiments indicated that addition of α-CD to the hydrogel of p(AA/C₁₂(5)) caused a drastic decrease in the viscosity, while addition of oligo(α-CD) to the solution of p(AA/C₁₂(2)) led to a remarkable increase in the viscosity.

Summary: The interaction of a polymer bearing β-cyclodextrin moieties (β-CD polymer) with poly(acrylamide)s bearing aromatic side chains was investigated by viscometry to study the effect of collectivity (i.e., interactions at multi-sites) in macromolecular recognition. The formation of inclusion complexes at multi-sites caused a large difference in the size of interpolymer aggregates, even though the difference in association constants for complexation of native β-CD with guest moieties was not very much large.

Summary: Polyisoprenes were found to form inclusion complexes with cyclodextrins with high selectivity to give crystalline compounds. β-Cyclodextrin formed complexes only with polyisoprene of low molecular weight, whereas γ-cyclodextrin formed complexes with polyisoprenes of high molecular weight. α-Cyclodextrin did not form complexes with polyisoprene of any molecular weight. The yields of γ-cyclodextrin complexes increased with increasing molecular weights of the polyisoprenes and reached a maximum of around several thousands, and then decreased.

Peroxidase activity of a complex of water-soluble cationic metalloporphyrin with anti-cationic porphyrin antibody is reported. Antibody 12E11G, which was prepared by immunization with a conjugate of 5-(4-carboxyphenyl)-10,15,20-tris(4-methylpyridyl)porphine iodide (3MPy1C), bound to tetramethylpyridylporphyrin iron complex (Fe^III–TMPyP) with the dissociation constant of 2.6×10⁻⁷ M. The complex of antibody 12E11G with Fe^III–TMPyP catalyzed oxidation of pyrogallol, catechol, and guaiacol. A Lineweaver–Burk plot for the oxidation of pyrogallol catalyzed by the Fe^III–TMPyP–antibody complex showed K_m=8.6 mM and k_cat=680 min⁻¹. Under the same conditions, K_m and k_cat for horseradish peroxidase (HRP) were 0.8 mM and 1750 min⁻¹, respectively. Although the binding interaction of the antibody to the substrates was one order lower than that of native HRP, the peroxidase activity of this system was in the same order of magnitude as that of HRP.

6-Cinnamoyl α-cyclodextrin (6-CiO-α-CD) and 6-cinnamoyl β-cyclodextrin (6-CiO-β-CD) were prepared. 6-CiO-α-CD formed intermolecular complexes to give supramolecular oligomers. 6-CiO-β-CD formed insoluble supramolecular complexes in the solid state. The structures of these complexes are discussed. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3519–3523, 2003

Poly(dimethylsilane)s form inclusion complexes with cyclodextrins in high selectivity to give crystalline compounds. β-Cyclodextrin forms complexes with poly(dimethylsilane)s of low molecular weight only, γ-cyclodextrin with poly(dimethylsilane)s of high molecular weight in high yield, and α-cyclodextrin does not form complexes with poly(dimethylsilane) at all. Complexes were isolated and characterized by spectroscopic methods and X-ray diffraction.

Polybutadienes were found to form inclusion complexes with cyclodextrins in high selectivity to give crystalline compounds. α-Cyclodextrin and β-cyclodextrin form complexes only with polybutadienes of low molecular weight and high 1,4-addition content. Polybutadienes with high 1,2-content gave complexes with γ-cyclodextrin in low yield. The yields of the γ-cyclodextrin complexes decreased with increasing molecular weights of the polybutadienes of similar composition. Complexes were isolated and characterized by means of FT-IR, ¹H NMR, ¹³C CP/MAS NMR, ¹³C PST/MAS NMR spectroscopies, and X-ray diffraction. Inclusion modes are discussed.

The complex formation between cyclodextrins (CDs) and poly(propylene glycol) (PPG) derivatives is described. β-CD and γ-CD formed complexes with PPG derivatives such as 1-naphthyl (1NA), 2-naphthyl (2NA), 3,5-dinitrobenzoyl, and 2,4-dinitrophenyl PPG. α-CD did not form complexes with these PPG derivatives. Although γ-CD gave complexes with 9-anthryl PPG (PPG9An), β-CD did not efficiently form complexes with PPG9An. β-CD did not form complexes with trityl PPG, demonstrating that trityl groups were too bulky to thread a β-CD cavity. The emission spectra of the complexes showed that β-CD bound a single 2NA moiety in its cavity and that γ-CD included two 2NA moieties. In contrast, γ-CD bound a single 1NA moiety in the cavity. X-ray diffraction studies and ¹H NMR analysis showed that the CD molecules were stacked along a PPG chain to form a channel structure. The inclusion modes are discussed. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4839–4849, 2000

Abstract Photoinduced electron transfer from tetrakis(4-carboxy-phenyl porphyrin)-zinc complex (Zn-TCPP) to an acceptor molecule (methyl viologen; MV²⁺) has been found to be controlled by the complex formation of monoclonal antibody 03-1 for the porphyrin (TCPP) and Zn-TCPP. Although there are no ground-state interactions between Zn-TCPP and MV²⁺ for a 2:1 complex of antibody 03-1 and Zn-TCPP, the fluorescence of Zn-TCPP is quenched by the addition of MV²⁺. The Stern-Volmer plots and emission lifetime studies show that there is a long-range electron transfer through the antibody 03-1.