岸川 圭希

The salts of 4-alkoxy-3,5-bis(hydroxymethyl) benzoic acids and alkylamine give stable smectic liquid crystals in a wide temperature range. These smectic phases were investigated by polarised optical microscopy, differential scanning calorimetry and powder X-ray diffraction. An inter-digitated structure of the plough-shaped network created by the inter-molecular hydrogen bonding between the hydroxymethyl groups in the direction of the molecular short axis is proposed.

Relation between the spontaneous polarization and alkyl chain length was investigated in ferroelectric switching of N,N'-bis(3,4,5-trialkoxyphenyl)urea (1-7) possessing n-C4H9, n-C8H17, n-C9H19, n-C10H21, n-C11H23, n-C12H25, and n-C16H33, respectively. The phase behaviors were investigated by differential scanning calorimetry, polarized optical microscopy, and the column diameters were obtained by X-ray diffraction. Compound 2-7 exhibited rectangular and hexagonal columnar phases. All of the hexagonal columnar phases showed ferroelectric switching under a triangular wave voltage. From the plot of the spontaneous polarization against the carbon atom number of the alkyl chains, correlation between them were clarified and it was strongly suggested that the switching current peaks originated in switching of the polar columns, not in the movement of ionic impurities.

Two approaches to create hydrogen-bonding (H-bonding) cyclic dimers of tethered benzoic acids in a crystalline state were examined. The cyclic dimers of the methoxy derivative 1 were generated by inclusion of aromatic guest molecules: benzene or benzonitrile, Depending on the size of the guests, the conformation of the pentylene linker of 1 took either the all-trans or 1,2- and 4,5-gauche conformation to adjust the size of the cavity for the guest. The tethered benzoic acids 2 possessing benzyloxy groups as pendants generated a poly(pseudo)rotaxane-like structure in which pendants were included in the cavity of the cyclic dimer itself. In contrast, 1 afforded a zigzag H-bonding network by recrystallization from methanol or ethanol. Incorporation of methanol in the zigzag network was observed when 1 was recrystallized from methanol.

-Nitro alcohols were converted to the corresponding nitro imines in the presence of lithium hexmethyldisilazide (LHMDS) in one pot. The formal transformation of the hydroxy to imino group proceeded in a sequence of the retro nitro-aldol reaction of -nitro alcohols and the double nitro-Mannich reaction of the resulting aldimines and nitro alkane dianions.

The phase behavior of N, N'-bis(3,4,5-trihexadecyloxyphenyl) urea (1) was investigated by differential scanning calorimetry, polarized optical microscopy, and X-ray diffraction. It was found that 1 exhibited two columnar phases, rectangular columnar and hexagonal columnar phases. The switching current peak (Ps approximate to 600nC/cm(2)) was observed under applying a triangular voltage with maintaining the homeotropic (dark) texture, which suggested that the polarities of the columns were changed by the applied triangular voltage without changing the directions of the column axes. The mechanism for the ferroelectric switching behavior was explained by the conformational isomerization of the urea moiety.

Upon ionic complexation of tris(2-aminoethyl)amine and di- or trialkoxybenzoic acids with normal and branched chains, hexagonal columnar mesophases were generated. The two parameters, the length and the cross-sectional area of the alkyl chains, were investigated to unveil the volume effect of the alkyl chains on the formation and stabilization of the columnar mesophases. The thermal stabilities of the columnar phases were strongly depended on the molar ratio of the acids to the amine. The highest clearing temperature (the most stable mesophase) was obtained at a ratio specific to the alkyl chain volume, not necessarily stoichiometric. We estimated the packing fraction (V-comp/V-cell) on the basis of the volume of the ionic complexes at these particular ratios (V-comp) and that of the unit cell of the Col(hex) phases (V-cell). The most suitable packing fractions for the Col(hex) phases of the present ammonium carboxylates were estimated to be in a range of 0.63-0.66.

Upon ionic complexation of tris(2-aminoethyl)amine and di- or trialkoxybenzoic acids with normal and branched chains, hexagonal columnar mesophases were generated. The two parameters, the length and the cross-sectional area of the alkyl chains, were investigated to unveil the volume effect of the alkyl chains on the formation and stabilization of the columnar mesophases. The thermal stabilities of the columnar phases were strongly depended on the molar ratio of the acids to the amine. The highest clearing temperature (the most stable mesophase) was obtained at a ratio specific to the alkyl chain volume, not necessarily stoichiometric. We estimated the packing fraction (V-comp/V-cell) on the basis of the volume of the ionic complexes at these particular ratios (V-comp) and that of the unit cell of the Col(hex) phases (V-cell). The most suitable packing fractions for the Col(hex) phases of the present ammonium carboxylates were estimated to be in a range of 0.63-0.66.

Introduction of lateral intermolecular interactions (dipole-dipole interactions, hydrogen bonds, and perfluoroarene-arene interactions) are attempted in rodlike and half-disklike molecules. In the cases of dicyanothiophenes, introduction of long cores stabilized their liquid crystal phases to give smectic and columnar phases, though the large lateral dipole in short rodlike molecules suppressed the molecular movements to destabilize the liquid crystal phases. Trialkoxybenzoic anhydrides were also organized into columnar aggregates by intermolecular dipole-dipole interaction. Further, molecules introduced a large lateral dipole at the center were useful for phase transition from smectic C to smectic CA phase. On the other hand, introduction of intermolecular hydrogen bonds in the direction of the molecular short axis generated novel smectic and cubic phases with strong hydrogen bonding. In the case of the liquid crystalline ureas, a switching behavior of the polarities was observed. Perfluoroarene-arene interaction was also useful to organize small molecules into a columnar superstructure.

A polymerizable benzoic acid derivative, 3,5-bis(propenoyloxymethyl)-4- hexadecyloxybenzoic acid (1), was synthesized and complexed in a molar ratio of 2:1 with each of the dipyridyl compounds 4,4 '-bipyridyl (2a), 1,2-dipyridylethane (2b), 1,2-dipyridylethene (2c), and 1,3-dipyridylpropane (2d). All of these 2:1 complexes exhibited a monotropic smectic A liquid crystal phase. Complex compound 1(2)center dot 2b (denoted 3b) in the liquid crystal phase was photopolymerized by UV irradiation. As the polymerization proceeded, the multilayered structure of 3b was maintained. In addition, the polymerizations of 3b containing the polymerizable rodlike compound PL at concentrations of 5 and 10 mol % also proceeded in the smectic A phases while maintaining their multilayered structures. By treatment with dilute hydrochloric acid for 216 h, all of the 2b molecules were removed from the polymer obtained from a Mixture of 3b and PL in a molar ratio of 90: 10, though only 50% of 2b could be removed from the polymer obtained from pure 3b. This suggested that PL molecules cross-linked each pair of polymer sheets and functioned as nanopillars between the two sheets.

Four-component synthesis of nitroimine derivatives (3) via double nitro-Mannich reaction was carried out in which nitroalkane, two moles of aldehyde, and lithium hexamethyldisilazide (LHMDS) were coupled in one-pot. In situ generated N-trimethylsilylaidimine was reacted with nitroalkane dianion followed by the second addition of the resulting nitrogen anion to the aldimine and the subsequent elimination of bistrimethylsilylamine furnished nitoroimine. The reaction was proceeded with erythro selectivity. (c) 2007 Elsevier Ltd. All rights reserved.

Conformation of aromatic foldamers possessing three aromatic rings in a sequence of anthracene - phenylene - anthracene linked with iminodicarbonyl was examined. Their folding structures were confirmed by single crystal X-ray analysis. Two conformations, straight-zigzag and helically-zigzag conformations, were found depending on the substituents at the imide nitrogen atom. Induced circular dichroism originated in the interaction of the upper and bottom anthracene moieties was observed both in solution and in the solid state. (c) 2007 Elsevier Ltd. All rights reserved.

The binary ionic liquid crystal composed of tris(2-aminoethyl)amine (1) and 3,4-dioctyloxybenzoic acid (2) was investigated. The type of the mesophases with the highest thermal stability was found to be specific to the 1-2 molar ratios; 1:2 for the smectic A phase and 1:4 for the hexagonal columnar phase.

Ionic liquid crystals based on ionic complexation of tris(2-aminoethyl)amine (1) with 3,4,5-tris(7,7,8,8,9,9,10,10,11,11,12,12,12-tridecafluorododecyloxy)benzoic acid (2) and with 3,4,5-tris(2-octyldodecyloxy)benzoic acid (3) were investigated. The ionic complex with the partially fluorinated alkyl chains (12) exhibited a morphological transition from a hexagonal columnar mesophase to a Pm3n micellar cubic phase upon increasing the molar ratio of 2 to 1. For the complex with the branched alkyl chains (13) a micellar cubic mesophase was exclusively generated at appropriate composite ratios. The generation of the micellar cubic mesophases is attributed to the introduction of the laterally expanded volume of the alkyl chains compared with the corresponding normal dodecyl chains. Their thermal stabilities were most enhanced at a specific molar ratio of 1:5 for 12 and 1:4 for 13. This result corresponds to the most suitable chain volume for the stable micellar cubic mesophase.

We have studied the polarization relaxation process after removing an applied electric field in the columnar hexagonal phase of N,N'-bis(3,4,5-trihexadecyloxyphenyl)urea by means of second-harmonic generation (SHG), switching current, and texture observation. Transient SHG and current associated by sudden field change show polarization switching associated with a molecular reorientation of about a few ms depending on the field strength. Furthermore, the texture observation reveals a column undulation process during 10 s to 1 min. The size of the polar domains was estimated to be 160 molecules by analyzing the field dependence of the SHG signal intensity on the basis of an Ising model.

In this work, we carried out ab initio molecular orbital theory calculations for phenylbenzoate and N-benzylideneaniline, by which we will interpret unusual phenomenon of compounds 1 and 2.

Liquid crystalline dimers consisting of two rodlike cores, two terminal alkyl chains and an oligo(ethylene glycol) spacer were synthesized. Their phase behaviors and structures were investigated by polarized optical micrograph (POM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD). These liquid crystalline dimers generated unconventional smectic layer structures in which the alkyl and oligo(ethylene glycol) chains micro-segregated in the chain layers. (c) 2006 Elsevier B.V. All rights reserved.

The authors have measured the electro-optic Kerr effect in the isotropic phase of a urea derivative. Electric-field-induced birefringence Delta n was observed in the isotropic phase even 30 degrees C above the isotropic-columnar phase transition temperature. The induced birefringence is inversely proportional to temperature, as predicted by the Landau-de Gennes theory. Two distinct regions are identified from the proportionality constants in the isotropic phase; optical second-harmonic generation (SHG) is easily observable in the low-temperature region on applying an electric field, whereas SHG activity does not emerge in the higher-temperature region. The structure of molecular assemblies is discussed based on these experimental results.

The authors have measured the electro-optic Kerr effect in the isotropic phase of a urea derivative. Electric-field-induced birefringence Deltan was observed in the isotropic phase even 30 degrees C above the isotropic-columnar phase transition temperature. The induced birefringence is inversely proportional to temperature, as predicted by the Landau-de Gennes theory. Two distinct regions are identified from the proportionality constants in the isotropic phase; optical second-harmonic generation (SHG) is easily observable in the low-temperature region on applying an electric field, whereas SHG activity does not emerge in the higher-temperature region. The structure of molecular assemblies is discussed based on these experimental results.

Fluorescence spectra of aromatic chain imides possessing anthracene and naphthalene moieties were examined both in solution and in the solid state. Depending on the substituents at the imide nitrogen atom, their fluorescence spectra varied in the solid state. However, their spectra in solution were almost identical. In solution, emission corresponding to a naphthalene-anthracene exciplex was observed. In contrast, the imides possessing an intermolecular anthracene-anthracene interaction exhibited red-shifted fluorescence in the solid state. This red-shifted fluorescence could originate in an anthracene excimer or the exciplex formed from a sum of fluorophores. In contrast, compounds without this anthracene-anthracene interaction in the solid state had very similar solution and solid-state fluorescence spectra.

Self-assembling building blocks that are readily functionalizable and capable of achieving programmed hierarchical organization have enabled us to create various functional nanomaterials. We have previously demonstrated that N,N'-disubstituted 4,6-diaminopyrimidin-2(1 H)-one (DAP), a guanine-cytosine hybridized molecule, is a versatile building block for the creation of tapelike supramolecular polymer species in solution. In the current study, DAP was functionalized with azobenzene side chains. 1H NMR, UV/Vis, and dynamic light scattering studies confirmed the presence of nanometer-scale tapelike supramolecular polymers in alkane solvents at micromolar regimes. At higher concentrations (millimolar regimes), the supramolecular polymers hierarchically organized into lamellar superstructures to form organogels, as shown by X-ray diffraction and polarized optical microscopy. Remarkably, the azobenzene side chains are photoisomerizable even in the supramolecular polymers, owing to their loosely packed state supported by the rigid hydrogen-bonded scaffold, enabling us to establish photocontrollable supramolecular polymerization and higher order organization of the tapelike supramolecular polymers into lamellar superstructures.

Fukuda， Kaoru; Nakahara， Shoichiro; Kishikawa， Keiki; Takanishi， Yoichi; Ishikawa， Ken; Watanabe， Junji; Takezoe， Hideo

Hydrogen-bonded disk-shaped aggregates (rosettes) composed of azobenzene-appended melamine and barbiturate or cyanurate are investigated in view of their hierarchical organization and photoresponsive behavior by (1)H NMR and UV/vis spectroscopies, dynamic light scattering, and gelation behavior in aliphatic solvents and liquid crystalline behavior in bulk state. In the bulk state the rosette possessing a sterically bulky tridodecyloxyphenyl substituent in the barbiturate component stacks in an offset arrangement to form a rectangular columnar mesophase, whereas in aliphatic solvents it does not hierarchically organize into higher-order columnar aggregates. This drawback is improved by exchanging the barbiturate component into a more sterically nondemanding N-dodecylcyanurate component. The resulting new rosette stacks in a face-to-face arrangement to form a hexagonal columnar mesophase in the bulk state and hierarchically organizes into elongated fibrous aggregates in cyclohexane, which eventually leads to the formation of organogel. Dynamic light scattering and UV-vis experiments upon UV-irradiation of the columnar aggregates in cyclohexane revealed that the dissociation and the reformation of columnar aggregates can be controlled by the trans-cis isomerization of the azobenzene moiety. Molecular modeling indicates that the rosette possessing cis-azobenzene side chains loses its planarity. Using this photoinduced morphological change of the rosette, photoresponsive organogel is created by the use of a disk-shaped supramolecule the first time.

[structure: see text] Carboxamides possessing naphthalene rings connected by multiple iminodicarbonyl linkers were synthesized. These molecules forced the naphthalene rings to be placed in the positions facing each other, and they form helical foldamers both in solution and in the crystalline state. Their folding structures were investigated by single-crystal X-ray analysis and (1)H NMR spectroscopy. Their absorption and fluorescence spectra showed a red shift as the number of naphthalene moieties increased. This remarkable change is based on the intramolecular interaction between naphthalene moieties. Helicity of the foldamer can be controlled by the introduction of chiral auxiliaries at imide nitrogen atoms, which results in an observation of induced circular dichroism.

Achiral rodlike molecules possessing an ester group generated a chiral smectic liquid crystal phase.

Calamitic liquid crystalline amides 1-3 were synthesized and their thermodynamic behaviors were investigated. Bent-rod shaped compound 1 exhibited a usual smectic C phase. On the other hand, in the case of straight-rod compound 2, two kinds of smectic C phases (SmCx and SmCy) were observed above the crystal phase. Although SmCy phase belonged to general smectic C phases, SmC. phase exhibited very sharp lines in its schlieren textures. As the packing model of smectic C-x phase, a lateral linear arrangement of the molecules was proposed to explain the difference between these smectic C phases. Additionally, in the case of 3 which has a flexible spacer between its amide group and straight rodlike core, the molecules generated the highly ordered smectic C (3a, SmCx) and a chiral cubic phase (3b).

The crystal structures of two aromatic chain imides, N-(naphthyl)-N-benzyl-9-phenanthylcarboxamide (1) and N-(9- anthrylcarbonyl)-N-{12-[9-anthryl-N-(phenylcarbonyl)carbonylamino]dodecyl}benzamide (2), were examined. In both imides, two aromatic moieties face each other, creating concave-shaped conformations. 2005 © The Japan Society for Analytical Chemistry.