10 research outputs found

    Correlation between Molecular Structure and Interfacial Properties of Edge or Basal Plane Modified Graphene Oxide

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    Although graphene oxide (GO) has been reported to be able to be edge functionalized or basal-plane functionalized separately, no research has been done on comparing both the molecular structure and interfacial properties of them. In this study, an alkyl amine was grafted to the epoxy group on the basal planes of GO (b-GO) and carboxyl group at the edges of GO (e-GO) separately by using different synthetic approach. With the combination of various molecular structure and morphology characterization methodologies, we proved that the reaction site for e-GO was only with the carboxyl group at the edge of GO and that for b-GO was epoxy group on the basal plane of GO, indicating that GO could be controllably functionalized (fGOs), and the structure of fGOs could be tuned. Study of the interfacial behavior of fGOs at liquid–liquid interface showed that the interfacial tension reducing capability of e-GO was broader than that of b-GO, and for alkyl oil phase, b-GO was slightly better than e-GO, and both were better than traditional nonionic surfactant. Study of the interfacial behavior of fGOs at liquid–solid interface demonstrated that, after absorption, b-GO arranged vertically on the metal surface, forming dense, compact, and strong film, while e-GO aligned horizontally to form loosely assembled film, resulting in higher interfacial shear strength than that of b-GO. Our results indicate the possibilities for tuning the interfacial properties of GO at both liquid–liquid and liquid–solid interfaces, which may be promising in the potential applications in controlled drug delivery, surface protection, absorption and separation, lubrication, nanocomposite, and catalyst fields

    Tetranitro-oxacalix[4]crown-Based Host–Guest Recognition Motif and a Related [2]Rotaxane-Based Molecular Switch

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    Different from so far reported oxacalix[4]­crown-based host–guest motifs in which oxacalix[4]­crowns act only as hydrogen bond acceptors, a [2]­pseudorotaxane-type tetranitro-oxacalix[4]­crown/urea host–guest recognition motif was developed in which tetranitro-oxacalix[4]­crown played a role as both a hydrogen bond donor and an acceptor to stabilize the resulting supramolecular complex. Furthermore, on the basis of a [2]­pseudorotaxane complex formed from a tetranitro-oxacalix[4]­crown and an axle containing a secondary ammonium ion and a urea group, a [2]­rotaxane-based molecular switch was created, in which the oxacalix[4]­crown wheel was able to reversibly translocate between the secondary ammonium binding site and the urea binding site of the axle under acid–base stimulation

    [2]Pseudorotaxanes and [2]Catenanes Constructed by Oxacalixcrowns/Viologen Molecular Recognition Motifs

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    Oxacalix­[2]­arene­[2]­pyrazine and functional polyether derived oxacalixcrown-6, -7, and -8 were synthesized, and their host–guest complexation with paraquat to form [2]­pseudorotaxanes was studied. The [2]­pseudorotaxanes were then successfully used in the construction of two oxacalixcrown-tetracationic cyclophane [CBPQT<sup>4+</sup>] based [2]­catenanes

    A1/A2-Diamino-Substituted Pillar[5]arene-Based Acid–Base-Responsive Host–Guest System

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    An acid–base-responsive supramolecular host–guest system based on a planarly chiral A1/A2-diamino-substituted pillar[5]­arene (1)/imidazolium ion recognition motif was created. The pillar[4]­arene[1]­diaminobenzene 1 can bring an electron-deficient imidazolium cation into its cylindrically shaped cavity under neutral or basic conditions and release it under acidic conditions

    Negative Cooperativity in the Binding of Imidazolium and Viologen Ions to a Pillar[5]arene-Crown Ether Fused Host

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    A pillar[5]­arene-crown ether fused bicyclic host <b>1</b> was found to be able to recognize an imidazolium ion <b>G1</b> by its pillar[5]­arene subunit and a viologen ion <b>G2</b> by its crown ether receptor discriminatively. The simultaneous binding of <b>G1</b> and <b>G2</b> by <b>1</b> resulted in the formation of a three-component host–guest complex <b>G1⊂1⊃G2</b>. Negative heterotropic cooperative effects were displayed by <b>G1</b> and <b>G2</b> in their binding to <b>1</b> and were investigated by stepwise bindings of <b>G1</b> and <b>G2</b> to <b>1</b>

    A1/A2-Diamino-Substituted Pillar[5]arene-Based Acid–Base-Responsive Host–Guest System

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    An acid–base-responsive supramolecular host–guest system based on a planarly chiral A1/A2-diamino-substituted pillar[5]­arene (<b>1</b>)/imidazolium ion recognition motif was created. The pillar[4]­arene[1]­diaminobenzene <b>1</b> can bring an electron-deficient imidazolium cation into its cylindrically shaped cavity under neutral or basic conditions and release it under acidic conditions

    A Shape-Persistent Cryptand for Capturing Polycyclic Aromatic Hydrocarbons

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    A shape-persistent cryptand <b>1</b>, containing two face-to-face oriented electron-deficient 2,4,6-triphenyl-1,3,5-triazine units separated by approximately 7 Å, and bridged by two rigid 1,8-naphthyridine linkers and a pentaethylene oxide loop, is created for capturing polycyclic aromatic hydrocarbons. Cryptand <b>1</b> formed 1:1 complexes with PAH guest molecules, such as phenanthrene (<b>6</b>), anthracene (<b>7</b>), pyrene (<b>8</b>), triphenylene (<b>9</b>), and tetraphene (<b>10</b>). The single-crystal structure of complex <b>6⊂1</b> revealed that <b>6</b> was included in the cavity of <b>1</b> via face-to-face π···π stacking interactions. Soaking crystalline <b>1</b> in a toluene solution of anthracene resulted in anthracene from the toluene solution being picked up by the crystalline solid of <b>1</b>

    Selectivity and Cooperativity in the Binding of Multiple Guests to a Pillar[5]arene–Crown Ether Fused Tricyclic Host

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    A novel tricylic host molecule <b>1</b> that consists of two pillar[5]­arene units and a crown ether ring was found to selectively bind two kinds of guest molecules with different shapes, sizes, and electronic constitutions, namely 1,4-dicyanobutane <b>G1</b> and paraquat <b>G2</b>, with its two macrocyclic subunits, to form a four-component complex <b>2G1⊂1⊃G2</b>. An <sup>1</sup>H NMR study of stepwise bindings of <b>G1</b> and <b>G2</b> to host <b>1</b> in CDCl<sub>3</sub>/DMSO-<i>d</i><sub>6</sub> revealed that the strength of the association between complex <b>2G1⊂1</b> and guest <b>G2</b> was only one-fourth of that between free <b>1</b> and <b>G2</b>, demonstrating a negative heterotropic cooperativity of <b>G1</b> in the binding of <b>G2</b> to host <b>1</b>

    Selectivity and Cooperativity in the Binding of Multiple Guests to a Pillar[5]arene–Crown Ether Fused Tricyclic Host

    No full text
    A novel tricylic host molecule <b>1</b> that consists of two pillar[5]­arene units and a crown ether ring was found to selectively bind two kinds of guest molecules with different shapes, sizes, and electronic constitutions, namely 1,4-dicyanobutane <b>G1</b> and paraquat <b>G2</b>, with its two macrocyclic subunits, to form a four-component complex <b>2G1⊂1⊃G2</b>. An <sup>1</sup>H NMR study of stepwise bindings of <b>G1</b> and <b>G2</b> to host <b>1</b> in CDCl<sub>3</sub>/DMSO-<i>d</i><sub>6</sub> revealed that the strength of the association between complex <b>2G1⊂1</b> and guest <b>G2</b> was only one-fourth of that between free <b>1</b> and <b>G2</b>, demonstrating a negative heterotropic cooperativity of <b>G1</b> in the binding of <b>G2</b> to host <b>1</b>

    Selectivity and Cooperativity in the Binding of Multiple Guests to a Pillar[5]arene–Crown Ether Fused Tricyclic Host

    No full text
    A novel tricylic host molecule <b>1</b> that consists of two pillar[5]­arene units and a crown ether ring was found to selectively bind two kinds of guest molecules with different shapes, sizes, and electronic constitutions, namely 1,4-dicyanobutane <b>G1</b> and paraquat <b>G2</b>, with its two macrocyclic subunits, to form a four-component complex <b>2G1⊂1⊃G2</b>. An <sup>1</sup>H NMR study of stepwise bindings of <b>G1</b> and <b>G2</b> to host <b>1</b> in CDCl<sub>3</sub>/DMSO-<i>d</i><sub>6</sub> revealed that the strength of the association between complex <b>2G1⊂1</b> and guest <b>G2</b> was only one-fourth of that between free <b>1</b> and <b>G2</b>, demonstrating a negative heterotropic cooperativity of <b>G1</b> in the binding of <b>G2</b> to host <b>1</b>
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