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ABSTRACT: Butyl and pentyl ether derivatives of (2-hydroxypropyl) cellulose (HPC) and butyl/pentyl mixed ethers of HPC (BPPC) with different alkyl compositions were prepared in nonaqueous solution and their thermotropic cholesteric properties examined. The temperature dependence and the composition dependence of the optical pitch, nP, were then determined for all of the ether derivatives. The molecular conformation and chirality of BPPC appeared to be to be variably smooth with the side chain composition of the polymer. The response rate of cholesteric configurational change of the thermotropic mesophases arising from a temperature jump from 45 to 75C, was also determined. The transformation of the cholesteric mesophase formed by an equimolar ether derivative (BP-50) was faster than that of the cholesteric one formed by a single-alkyl (pentyl) ether derivative (BP-0). This seemed to be a general result reflecting a pseudo-copolymer effect of cellulose derivatives on the properties of their thermotropic cholesteric mesophases.
Cellulose 04/2012; 13(3):205-211. · 3.60 Impact Factor
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ABSTRACT: We monitored the progress of formation of dimethoxypillar[5]arene by size-exclusion chromatography. Surprisingly, the cyclization reaction completely finished in just 3 min. By improving the reaction conditions and purification process, we successfully obtained dimethoxypillar[5]arene in a short time and in high yield (71%) from commercially available reagents. By improving the deprotection reaction of the methoxy moieties, pillar[5]arene was isolated quantitatively. Single crystal X-ray analysis confirmed the structure of pillar[5]arene in the solid state.
The Journal of Organic Chemistry 01/2011; 76(1):328-31. · 4.45 Impact Factor
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ABSTRACT: We synthesized chiral-substituents modified pillar[5]arene for the first time. The chiral-substituents modified pillar[5]arene showed planar chirality and interconversion between (pS) and (pR) forms took place quickly. The planar chirality was switched by temperature, solvents, and addition of achiral guest. As the measurement temperature increased, the diastereomeric excess was decreased. The diastereomeric excesses were high in low-permittivity solvents, while a low diastereomeric excess was observed in high-permittivity solvents. Addition of achiral guest induced an increase of negative CD intensities.
The Journal of Organic Chemistry 01/2011; 76(2):618-22. · 4.45 Impact Factor
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ABSTRACT: The preparation of a hybrid of graphene oxide and per-6-amino-beta-cyclodextrin is reported. The hybrid formed a supramolecular graphene oxide polymer network upon addition of guest dimer.
Chemical Communications 09/2010; 46(33):6087-9. · 6.17 Impact Factor
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ABSTRACT: New polyrotaxane composed of pillar[5]arene and viologen polymer was successfully prepared with extremely high yield by capping the chain ends with adamantyl moieties. Pillar[5]arene and viologen polymer are soluble in various solvents such as acetone, acetonitrile, methanol, DMF, and DMSO, while the polyrotaxane was soluble in DMF and DMSO and insoluble in the other organic solvents. Formation of inter-molecular hydrogen bonds between the OH moieties of pillar[5]arenes stabilized the structure and reduced the solubility. The polyrotaxane exhibited a thermally induced color change from yellow to violet. On heating, the inter-molecular hydrogen bond became weakened, and the shuttling motion of pillar[5]arenes on the polymer axis was fast. Thus, efficient electron transfer from the electron donors of pillar[5]arenes to the electron acceptor of viologen polymer occurred in the whole polymer chain and the radical cation species were stabilized.
08/2010;
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ABSTRACT: A series of pillar[5]arene derivatives with alkyl groups of different length were synthesized. The new alkyl-substituted pillar[5]arene derivatives 1,4-bis(ethoxy)pillar[5]arene (C2), 1,4-bis(propoxy)pillar[5]arene (C3), 1,4-bis(butoxy)pillar[5]arene (C4), 1,4-bis(pentyloxy)pillar[5]arene (C5), 1,4-bis(hexyloxy)pillar[5]arene (C6), and 1,4-bis(dodecanoxy)pillar[5]arene (C12) were obtained by Lewis acid-catalyzed condensation of dialkoxybenzene monomers with paraformaldehyde. The conformational characteristics of the pillar[5]arene derivatives were investigated by dynamic (1)H NMR measurements. When the alkyl substituents were bulkier than methyl groups, the rotation of phenolic units in the pillar[5]arenes was suppressed and their conformation was immobilized. As their length increased, the alkyl substituents packed at the upper and lower rims and thus lowered the conformational freedom of the pillar[5]arenes.
The Journal of Organic Chemistry 05/2010; 75(10):3268-73. · 4.45 Impact Factor
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ABSTRACT: Water-soluble pillar[5]arene was synthesized by the introduction of carboxylate anions at both upper and lower rims. When cationic viologen salt was mixed with the water-soluble pillar[5]arene in aqueous media, a very stable 1:1 host-guest complex was formed.
Chemical Communications 04/2010; 46(21):3708-10. · 6.17 Impact Factor
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03/2010;
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ABSTRACT: A new nonsymmetric pillar[5]arene of ethoxymethoxypillar[5]arene (EMpillar[5]arene) has been synthesized. By 2D ROESY analysis of EMpillar[5]arene, the ethoxy and methoxy moieties were completely separated at the upper and lower rims, respectively. Moreover, by the variable-temperature (1)H NMR measurements of EMpillar[5]arene, the rotational movement of phenolic units in EMpillar[5]arene was slow on the NMR time scale or did not occur.
Organic Letters 02/2010; 12(3):636-8. · 5.86 Impact Factor
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ABSTRACT: The rotation behavior of the phenolic units in pillar[5]arenes has been studied by means of the dynamic 1H NMR measurements. In acetone-d6, the individual conformers of pillar[5]arene were observed under −60 °C, indicating that the rotation movement was slow on the NMR time scale under −60 °C. In permethylated pillar[5]arene in acetone-d6, the peaks were not split even at −90 °C, strongly suggesting that the rotation movement was fast on the NMR time scale at −90 °C. This is due to the lack of the intramolecular hydrogen bond belt in permethylated pillar[5]arene. In the mixture of pillar[5]arene and viologen guest in acetone-d6, the split peaks were found at −30 °C and did not change under −60 °C. By formation of the host−guest complex between pillar[5]arene and viologen guest, the rotation movement was slow on the NMR time scale under −30 °C and almost stopped under −60 °C.Keywords (keywords): pillar[5]arene; permethylated pillar[5]arene; intramolecular hydrogen bond belt; variable-temperature 1H NMR measurements; rotation; host−guest complex
02/2010;
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11/2009;
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ABSTRACT: We report supramolecular assemblies of a beta-cyclodextrin dimer linked at both ends of a fluorescent phenylethynylpyrene moiety (Py-beta-CD dimer). The Py-beta-CD dimer formed supramolecular associations in aqueous media due to the pi-pi stacking of the hydrophobic phenylethynylpyrene moiety. From tapping mode atomic force microscopy measurements, the Py-beta-CD dimer formed wire-shaped assemblies in aqueous media. By adding sodium adamantane carboxylate to the supramolecular assemblies, the structural change to J-type assemblies was observed. In contrast, upon addition of the electron-deficient guest, the electron transfer from the electron rich phenylethynylpyrene moiety of the supramolecular assemblies to the electron-deficient guest took place.
Langmuir 11/2009; 26(5):3169-73. · 4.19 Impact Factor
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ABSTRACT: Pillar[5]arene from modified phenylethynyl groups was prepared; since the repeating pi-conjugated units were largely pi-delocalized via the through-space within the cavity, it showed temperature- and solvent-responsive blue-green emission.
Chemical Communications 09/2009; · 6.17 Impact Factor
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ABSTRACT: We report on synthesis, association behavior, and application of six-arm star-shaped and tadpole-shaped amphiphilic polyoxazolines from triphenylene initiators. We synthesized two kinds of novel triphenylene initiators: 2,3,6,7,10,11-hexa(6-bromohexyloxy)triphenylene (initiator for star-shaped polyoxazoline) and 2-(6-bromohexyloxy)-3,6,7,10,11-pentahexyloxytriphenylene (initiator for tadpole-shaped polyoxazoline). Ring-opening cationic polymerization of 2-methyl-2-oxazoline from these initiators successfully produced star- and tadpole-shaped polyoxazolines. Both the star- and tadpole-shaped polyoxazolines formed supramolecular associations in aqueous media due to π−π stacking of hydrophobic triphenylene moiety. Critical micelle concentrations (CMCs) and amounts of π−π stacking of the star- and tadpole-shaped polyoxazolines in aqueous media were investigated by 1H NMR and fluorescence measurements. From tapping mode atomic force microscopy (TM-AFM) measurements, the star-shaped polyoxazolines formed straight columnar stacks due to π−π stacking of hydrophobic disklike core of triphenylene moiety and symmetric star-shaped structure. In contrast, crooked nanowires were observed in the tadpole-shaped polyoxazoline. Tadpole shape was asymmetric, and thus ordered π−π stacking of hydrophobic triphenylene moiety was suppressed. Moreover, by using the columnar stacks of the star-shaped polyoxazoline as a template, we successfully synthesized wire-assembled gold nanoparticles.
04/2009;
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ABSTRACT: Polymerization of phenol with paraformaldehyde and catalytic sulfuric acid was carried out in room temperature ionic liquids based on imidazolium salts. The properties of ionic liquids were systematically varied by employing six different anions such as chloride, bromide, iodide, tetrafluoroborate, trifluoromethanesulfonate and hexafluorophosphate. In case of hydrophilic ionic liquids having chloride or bromide anion, phenol polymers with low molecular weight and narrow polydispersity were obtained. In contrast, using hydrophobic ionic liquids such as tetrafluoroborate and trifluoromethanesulfonate anions, high molecular weight phenol polymers were prepared. It is because interaction of the hydrophilic ionic liquids with phenol is stronger than that of the hydrophobic ionic liquids. The interaction between phenol and ionic liquids was investigated by 1H NMR measurements. Moreover, by using Brønsted acid ionic liquid carrying sulfuric acid moiety as a solvent, catalytic acid-free green polymerization of phenol with paraformaldehyde was accomplished. The ionic liquid was efficiently recovered and reused in new polymerization process of phenol.
10/2008;
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ABSTRACT: Solubilization of single-walled carbon nanotubes (SWNTs) by physical adsorption of cyclodextrins (CDs), guest molecules, and host−guest complexes was investigated. As guest compounds, sodium adamantanecarboxylate (AdCNa), sodium dodecylbenzenesulfonate (SDBS), sodium ursodeoxycholate (UdCNa), sodium ferrocenecarboxylate (FeCNa), and TritonX-405 were employed. As host compounds, α-, β-, and γ-cyclodextrins (α-, β-, and γ-CDs) were used. By using CDs as a solubilizing agent, SWNTs were insoluble in aqueous media. In the presence of AdCNa and FeCNa, solubility of SWNTs was dramatically increased by formation of host−guest complex with β- or γ-CDs. By using SDBS-CD complexes, solubility of SWNTs was also enhanced compared to only guest molecules. On the other hand, solubility of SWNTs was decreased by formation of host−guest complexes of UdCNa and TritonX-405 with CDs. Formation of host−guest complex mostly resulted in enhancement of water solubility of SWNTs.
07/2008;
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ABSTRACT: Single-walled carbon nanotubes (SWCNTs) were suspended in aqueous media with cucurbit[7]uril (CB7), while SWCNTs were insoluble with cucurbit[5]uril (CB5). Moreover, defection-selective solubilization of SWCNTs with CB7 was demonstrated.
Chemical Communications 06/2008; · 6.17 Impact Factor
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ABSTRACT: Condensation of 1,4-dimethoxybenzene (DMB) with paraformaldehyde in the presence of BF3.O(C2H5)2 gave novel para-bridged pentacyclic pillar DMB (DMpillar[5]arene). Moreover, para-bridged pentacyclic hydroquinone (pillar[5]arene) was prepared. Pillar[5]arene formed 1:1 host-guest complexes with dialkyl viologen and alkyl pyridinium derivatives. However, pillar[5]arene did not form complexes with the diadamantyl viologen derivative since a bulky adamantyl group was unable to thread the cavity of pillar[5]arene.
Journal of the American Chemical Society 05/2008; 130(15):5022-3. · 9.91 Impact Factor
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ABSTRACT: We report on hybrids of water-soluble calix[8]arenes and single-walled carbon nanotubes (SWCNTs); the hybrids formed supramolecular SWCNTs network polymer by adding guest dimer.
Chemical Communications 01/2008; · 6.17 Impact Factor
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ABSTRACT: The Effect of hydroxy isothiocyanates on a bacterial virus and M13 DNA was examined. Hydroxy-substituted phenyl and phenyl alkyl isothiocyanates, especially 2-(3,4-dihydroxyphenyl)ethyl isothiocyanate(IT-Dop) synthesized from dopamine, showed antiviral activity on psiK. In transfection experiments with M13 mp DNA species, IT-Dop inhibited the single-stranded (SS) molecule more effectively than the double stranded replicative form (RF) DNA. These effects were dependent on reaction time, and on IT-Dop concentration. An additional experiment indicated that treatment with IT-Dop suppressed annealing (reassociation) of denatured DNA. These results indicate that IT-Dop reacts mildly with virus and SS DNA.
Bioscience Biotechnology and Biochemistry 05/2007; 71(4):1094-7. · 1.28 Impact Factor
