Gold Nanoparticles Carrying Diatomic Molecules (O2 and CO) in Aqueous Solution

Gold nanoparticles (AuNPs) prepared by citrate reduction of aurochloric acid (HAuCl₄) were functionalized by tris(4‐sulfonatophenyl)porphinatoiron(III) (Fe^IIIP2) and poly(ethylene glycol) with thiolated arms (PEG‐SH). Fe^IIIP2 on the AuNP surface existed as its μ‐oxo dimer, which was reduced by Na₂S₂O₄ to yield monomeric Fe^IIP2. Fe^IIP2‐bearing AuNPs were further functionalized through inclusion of two sulfonatophenyl groups of Fe^IIP2 by a per‐O‐methylated β‐cyclodextrin dimer with a pyridine linker (Py3CD) to obtain AuNPs capable of carrying diatomic molecules in the body. The resulting AuNPs (hemoCD‐AuNPs) bound O₂ as well as CO in an aqueous solution. Although a noncolloidal 1:1 complex of 5,10,15,20‐tetrakis(4‐sulfonatophenyl)porphinatoiron(II) and Py3CD injected into the femoral vein of a rat was rapidly excreted in the urine, no excretion was observed with ferric hemoCD‐AuNPs, which were gradually accumulated in the spleen and liver of a rat. These results suggest that hemoCD‐AuNPs can be used as a carrier of diatomic molecules such as O₂ and CO in vivo.     

Hydrogels Composed of Organic Amphiphiles and α‐Cyclodextrin: Supramolecular Networks of Their Pseudorotaxanes in Aqueous Media

Mixtures of N‐alkyl pyridinium compounds [py‐N‐(CH₂)_nOC₆H₃‐3,5‐(OMe)₂]⁺(X^?) ( 1b Cl: n=10, X=Cl; 1c Br: n=12, X=Br) and α‐cyclodextrin (α‐CD) form supramolecular hydrogels in aqueous media. The concentrations of the two components influences the sol–gel transition temperature, which ranges from 7 to 67 °C. Washing the hydrogel with acetone or evaporation of water left the xerogel, and ¹³C CP/MAS NMR measurements, powder X‐ray diffraction (XRD), and scanning electron microscopy (SEM) revealed that the xerogel of 1b Cl (or 1c Br) and α‐CD was composed of pseudorotaxanes with high crystallinity. ¹³C{¹H} and ¹H NMR spectra of the gel revealed the detailed composition of the components. The gel from 1b Cl and α‐CD contains the corresponding [2]‐ and [3]pseudorotaxanes, [ 1b? (α‐CD)]Br and [ 1b? (α‐CD)₂]Br, while that from 1c Br and α‐CD consists mainly of [3]pseudorotaxane [ 1c? (α‐CD)₂]Br. 2D ROESY ¹H NMR measurements suggested intermolecular contact of 3,5‐dimethoxyphenyl and pyridyl end groups of the axle component. The presence of the [3]pseudorotaxane is indispensable for gel formation. Thus, intermolecular interaction between the end groups of the axle component and that between α‐CDs of the [3]pseudorotaxane contribute to formation of the network. The supramolecular gels were transformed into sols by adding denaturing agents such as urea, C₆H₃‐1,3,5‐(OH)₃, and [py‐N‐nBu]⁺(Cl^?).     

Mechanistic Study of the Solvent-Dependent Formation of Extended and Stacked Supramolecular Polymers Composed of Bis(imidazolylporphyrinatozinc) Molecules

Bis(imidazolylporphyrinatozinc) molecules linked through a 1,3-butadiynylene moiety respond to the solvents they are dissolved in to afford exclusively extended (E) or stacked (S) supramolecular polymers. This system is expected to be a solvation/desolvation indicator. However, the principles underlying the solvent-dependent formation of the two types of polymers and the mechanism of the transformation between them are unclear. The formation of the polymers is considered to depend on the two types of complementary coordination bonds that can be formed and the π–π interactions between the porphyrins. In this study, the contributions and solvent dependence of both the coordination bonds and the π–π interactions have been investigated. The results clearly indicate that the coordination bonds are weakly or little solvent-dependent, and that the π–π interactions function effectively only in the inner porphyrins of the S-polymer and are strongly solvent-dependent. Thermodynamic analysis revealed that the formation of the E- or S-polymer in solution is determined by the total energies and the type of solvent used. The transformation of the E- to S-polymer was investigated by gel permeation chromatography. The kinetics of the transformation were also determined. The role of the terminal imidazolylporphyrinatozinc moieties was also investigated: The results indicate that the transformation from the E- to S-polymer occurs by an exchange mechanism between the polymers, induced by attack of terminal free imidazolyl groups on a polymer to zinc porphyrins on other polymers.     

Complex Formation Between Poly(dimethylsilane) and Cyclodextrins

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.     

Stereospecific Cyclic Poly(methyl methacrylate) and Its Topology‐Guided Hierarchically Controlled Supramolecular Assemblies

In this study, the stereocomplexation between a novel stereospecific cyclic vinyl polymer, that is, cyclic syndiotactic poly(methyl methacrylate) (st‐PMMA), with the complementary linear isotactic (it‐) PMMA was investigated. Surprising new insight into the effects of the topology (i.e., end groups), size, and tacticity of the assembling components on stereocomplex formation was obtained. Characterization of the stereocomplexes revealed that the self‐assembly of cyclic st‐PMMAs and linear it‐PMMAs resulted in the formation of an unprecedented “polypseudorotaxane‐type” supramolecular assembly. This stereocomplex exhibited remarkably different physical properties as compared to the conventional PMMA triple‐helix stereocomplex as a result of the restricted topology imposed by the cyclic st‐PMMA assembling component.     

Poly(p-phenylene ethynylene)s with facially amphiphilic pendant groups: solvatochromism and supramolecular assemblies

Novel functionalized poly(p-phenylene ethynylene)s (PPEs) bearing facially amphiphilic cholic and deoxycholic acid units are synthesized by a Pd-catalyzed Sonogashira cross-coupling reaction. Some interesting properties, particularly their optical and self-assembly characteristics, are unraveled. The PPEs that carry bile acid substituents exhibit remarkable solvatochromism in a wide range of solvent systems, and judicious choice of the solvents can adjust the size and morphology of the formed nanoscale supramolecular aggregates. The incorporation of these naturally occurring building blocks can also impart biocompatibility to the conjugated system and stimulate the growth of living cells.     

Synthesis and Thermoreversible Gelation Properties of Main‐Chain Poly(pyridine‐2,6‐dicarboxamide‐triazole)s

A series of main‐chain poly(amide‐triazole)s were prepared by copper(I)‐catalyzed alkyne–azide AABB‐type copolymerizatons between five structurally similar diacetylenes 1 – 5 with the same diazide 6 . The acetylene units in monomers 1 – 5 possessed different degrees of conformational flexibility due to the different number of intramolecular hydrogen bonds built inside the monomer architecture. Our study showed that the conformational freedom of the monomer had a profound effect on the polymerization efficiency and the thermoreversible gelation properties of the resulting copolymers. Among all five diacetylene monomers, only the one, that is, 1 ‐Py(NH)₂ which possesses the pyridine‐2,6‐dicarboxamide unit with two built‐in intramolecular H bonds could produce the corresponding poly(amide‐triazole) Poly‐(PyNH)₂ with a significantly higher degree of polymerization (DP) than other monomers with a lesser number of intramolecular H bonds. In addition, it was found that only this polymer exhibited excellent thermoreversible gelation ability in aromatic solvents. A self‐assembling model of the organogelating polymer Poly‐(PyNH)₂ was proposed based on FTIR spectroscopy, XRD, and SEM analyses, in which H bonding, π–π aromatic stacking, hydrophobic interactions, and the structural rigidity of the polymer backbone were identified as the main driving forces for the polymer self‐assembly process.     

Synthesis of Doubly Ethyl‐Bridged Bis(p‐sulfonatocalix[4]arene) and Its Supramolecular Polymerization with Viologen Dimer

A water‐soluble supramolecular polymer with a high degree of polymerization and viscosity has been constructed based on the strong host–guest interaction between p‐sulfonatocalix[4]arenes (SC4As) and viologen. A homoditopic doubly ethyl‐bridged bis(p‐sulfonatocalix[4]arene) (d‐SC4A) was prepared and its binding behavior towards methyl viologen compared with the singly ethyl‐bridged bis(p‐sulfonatocalix[4]arene) (s‐SC4A) by NMR spectroscopy and isothermal titration calorimetry. By employing a viologen dimer (bisMV⁴⁺) as the homoditopic guest, two linear AA/BB‐type supramolecular polymers, d‐SC4A?bisMV⁴⁺ and s‐SC4A?bisMV⁴⁺, were successfully constructed. Compared with s‐SC4A?bisMV⁴⁺, d‐SC4A?bisMV⁴⁺ shows much higher solubility and viscosity, and has also been characterized by viscosity, diffusion‐ordered NMR spectroscopy, dynamic light scattering, and atomic force microscopy measurements. Furthermore, the polymer is responsive to electrostimulus as viologen is electroactive, which was studied by cyclic voltammetry. This study represents a proof‐of‐principle as the polymer can potentially be applied as a self‐healing and degradable polymeric material.     

Glucose Oxidase and Glucose for Redox‐Initiating the Free Radical Copolymerization of N‐(ferrocenoylmethyl)acrylamide in Aqueous Cyclodextrin Solution

The glucose oxidase and glucose mediated formation of amphipilic copolymers of N‐(ferrocenoylmethyl)acrylamide (NFMA) and N,N‐diethylacrylamide (DEA) in aqueous cyclodextrin solution is presented. Thereby, NFMA is not only a comonomer but also part of the redox initiation system. The obtained copolymers contain NFMA units between 1 and 10 mol%. The molecular masses of the copolymers are dependent on the ferrocene content, whereupon molecular weights between 38 000 and 71 000 g mol⁻¹ are achieved.

     

Free Superoxide is an Intermediate in the Production of H2O2 by Copper(I)‐Aβ Peptide and O2

Oxidative stress is considered as an important factor and an early event in the etiology of Alzheimer's disease (AD). Cu bound to the peptide amyloid‐β (Aβ) is found in AD brains, and Cu‐Aβ could contribute to this oxidative stress, as it is able to produce in vitro H₂O₂ and HO^. in the presence of oxygen and biological reducing agents such as ascorbate. The mechanism of Cu‐Aβ‐catalyzed H₂O₂ production is however not known, although it was proposed that H₂O₂ is directly formed from O₂ via a 2‐electron process. Here, we implement an electrochemical setup and use the specificity of superoxide dismutase‐1 (SOD1) to show, for the first time, that H₂O₂ production by Cu‐Aβ in the presence of ascorbate occurs mainly via a free O₂^.? intermediate. This finding radically changes the view on the catalytic mechanism of H₂O₂ production by Cu‐Aβ, and opens the possibility that Cu‐Aβ‐catalyzed O₂^.? contributes to oxidative stress in AD, and hence may be of interest.     

Supramolecular Terbium-SIP Complex Pillared by 4,4＇-Bipyridyl, {[Tb（SIP）（H2O）5]2（bpy）3（H2O）}n： Synthesis,Crystal Structure and Photoluminescence

The supramolecular terbium complex, {[Tb（SIP）（H2O）5]2（bpy）3（H2O）}n （NaH2SIP = 5-sulfoisophthalic acid monosodium salt and bpy = 4,4＇-bipyridyl）, has been synthesized by the hydrothermal reaction of Tb4O7 with NaH2SIP and bpy at 165 ℃, and characterized by single-crystal X-ray diffraction, elemental analysis, IR spectrum, powder X-ray diffraction and photoluminescence spectrum. It crystallizes in a monoclinic system, space group C2/c, with a = 30.6840（1）, b = 10.9206（2）, c = 17.4967（3） A, β= 111.931（1）°, V = 5438.65（14） A^3, Z = 4, C46H52N6O25S2Tb2, Mr = 1470.90, Dc = 1.796 g/cm^3, p = 2.747 mm^-1, F（000） = 2928, the final R = 0.0654 and wR = 0.1322 for 3806 observed reflections with I 〉 2σ（I）. In the neutral [Tb（SIP）（H2O）5]2 motif, the Tb（III） ions are linked by the SIP ligands to form a one-dimensional zigzag chain propagating along the c axis. The zigzag chains are linked together by hydrogen bonds and π-π stacking interactions to form a two-dimensional supramolecular framework. The uncoordinated bpy molecules act as pillars to extend the two-dimensional sheets into a distinctive pillared three-dimensional supramolecular structure through O-H...N hydrogen bonds. The photoluminescence of the complex was investigated at room temperature in the solid state.     

Study on Synergistic Effect Between Wormlike Micelles and Hydrophobically Modified Poly(acrylic acid) in Salt Solution

The complex system of hydrophobically modified poly (acrylic acid) (HMPA) and wormlike micelles formed by sodium oleate in the presence of sodium acetate is investigated by apparent viscosity and rheological measurements. Addition of small amount of HMPA markedly enhances the viscosity of wormlike micelles, with further increase of HMPA concentration, a viscosity drop is observed. At high salinity, the complex system still remains strong viscoelastic and eliminates the limitation of susceptibility to salt for HMPA. DPD simulation results are in good agreement with experimental data, which provide theoretical confirmation for a synergistic mechanism between HMPA and wormlike micelles.      

Synthesis and Crystal Structure of Two-dimensional Network Supramolecular Complex [Cu(dafo)_2(H_2O)_2](ClO_4)_2

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Supramolecular Phosphatases Formed by the Self‐Assembly of the Bis(Zn2+–Cyclen) Complex,Copper(II), and Barbital Derivatives in Water

In our previous paper, we reported that a dimeric Zn²⁺ complex with a 2,2′‐bipyridyl linker (Zn₂L¹), cyanuric acid (CA), and a Cu²⁺ ion automatically assemble in aqueous solution to form 4:4:4 complex 3 , which selectively catalyzes the hydrolysis of mono(4‐nitrophenyl)phosphate (MNP) at neutral pH. Herein, we report that the use of barbital (Bar) instead of CA for the self‐assembly with Zn₂L¹ and Cu²⁺ induces 2:2:2 complexation of these components, and not the 4:4:4 complex, to form supramolecular complex 6 a , the structure and equilibrium characteristics of which were studied by analytical and physical measurements. The finding show that 6 a also accelerates the hydrolysis of MNP, similarly to 3 . Moreover, inspired by the crystal structure of 6 a , we prepared barbital units that contain functional groups on their side chains in an attempt to produce supramolecular phosphatases that possess functional groups near the Cu₂(μ‐OH)₂ catalytic core so as to mimic the catalytic center of alkaline phosphatase (AP).     

Complex Formation of Cyclodextrins with Various Thiophenes and their Polymerization in Water: Preparation of Poly-pseudo-rotaxanes containing Poly(thiophene)s

Cyclodextrins (α-CD, β-CD and 2,6-di-O-dimethyl-β-CD (DM-β-CD)) were found to form inclusion compounds with thiophenes (thiophene (T), bithiophene (2T)) in water and in crystalline states. The structures of α-CD–T, β-CD–2T, and DM-β-CD–2T inclusion complexes were determined by X-ray crystallography. DM-β-CD forms a 1:1 cage type complex with 2T. In contrast, β-CD formed 2:3 (CD:guest) complexes with thiophene and α-CD formed 2:3 complexes, both of the channel type. These inclusion complexes were found to polymerize by FeCl₃ in the inclusion compounds in water. The products were formed poly-pseudo-rotaxane between cyclodextrins and poly(thiophene) characterized by IR, ¹H-NMR and ¹³C CP/MAS NMR. The molecular weights of the poly-pseudo-rotaxanes with poly(thiophene) were determined by the MALDI-TOF mass spectra to be 3000–5000. In comparison between poly-pseudo-rotaxane (DM-β-CD–poly(thiophene)), authentic poly(thiophene) and the washed DM-β-CD–poly(thiophene) which was washed with DMF to dethread DM-β-CD, these poly-pseudo-rotaxane was characterized by Raman, UV–vis and fluorescence spectra. The maximum emission band of DM-β-CD–poly(thiophene) shifted to a shorter wavelength. The hypsochromic shift was derived from poly-pseudo-rotaxane with DM-β-CD.