Nobuhiko Miyajima

Effects of Branching of the Ester Alkyl Chain on the Liquid Crystalline Properties of Alkyl 4-[4-(4-Substituted benzylideneamino)benzoyloxy]benzoates

Abstract The liquid crystalline properties of four homologous series of alkyl 4-[4-(4-X-substituted benzylideneamino) benzoyloxy]benzoates, where X = NO2, CI, CH3, and CH3O, have been compared with each other. The ester alkyl groups employed were the following twelve; propyl, butyl, pentyl, and their monomethyi-substituted ones. While all the members of the nitro derivatives are purely nematogenic, the other three series exhibit both nematic and smectic A phases but the former mesophase is mostly eliminated by 1-methylation. The nematic-isotropic transition temperature varies alternately when the branching methyl group shifts from the odd to even position in the alkyl chain. The change in the thermal stability of the smectic A phase by chain branching depends considerably upon the alkyl chain length and also upon the nature of the substituent X located at the other end of the molecule. Some branched alkyl esters attain a smectic A-nematic transition temperature higher than that of the corresponding unbran...

Effects of Branching of the Alkyl Chain on the Liquid Crystalline Properties of N-(p-Phenylbenzylidene)-p-Alkoxycarbonylanilines

Abstract The Liquid crystal behavior of twenty-three N-(p-phenylbenzylidene)-p-alkoxycarbonyl-anilines has been examined by optical microscopy and differential scanning calorimetry in order to study the effects of branching of the alkyl groups. Among the results obtained, the following are particularly of interest: (1) the effect of methyl group(s) on the penultimate carbon of the propyl ester on the nematic thermal stabilities is essentially nil or small, (2) the emergence of a nematic Liquid crystal is achieved by 2-methylation of the purely smectogenic butyl and pentyl esters, and (3) the thermal stability of smectic phase is not always decreased by methylation but is increased in some cases.

Mesomorphic behaviour of four series of compounds derived from N,N′-dialkanoylbenzene-1,3-diamine

Syntheses, differential scanning calorimetric (DSC) and X-ray diffraction (XRD) studies were carried out on the following four series of compounds: the 5-methyl-2-alkanoyloxy, 4,5-dimethyl-2-alkanoyloxy, 2-methyl-5-tert-butyl-4-methoxy and 2,5,6-trimethyl-4-hydroxy derivatives of N,N′-dialkanoylbenzene-1,3-diamine. The high-temperature phases given by the first and second series are viscous fluids. On supercooling of the isotropic liquid, a hexagonal ordered columnar phase appears, as demonstrated by the XRD pattern. This behaviour is in sharp contrast to that of the 2,5-dimethyl-4-alkanoyloxy derivatives, which are isomeric with compounds of the second series and nematogenic. Many homologous members in the third and fourth series exhibit a nematic phase. The methoxy group introduced to the 4-position of the 2-methyl-5-tert-butyl derivative leads to a significant depression of the clearing point relative to the parent compound.

Effects of Branching of the Ester Alkyl Chain on the Liquid Crystalline Properties of Alkyl 4-(4-Alkoxybenzylideneamino)- benzoates

Abstract The liquid crystalline properties of alkyl 4-(4-alkoxybenzylideneamino)benzoates, where the ester alkyl groups are propyl, isobutyl, neopentyl, racemic 2-methylbutyl, pentyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, and 4-methylpentyl, have been studied by thermal microscopy and differential scanning calorimetry. The alkoxyl group includes all the members from methoxyl to decyloxyl in most of the series. Chain branching of the purely smectogenic five propyl, two butyl, and six pentyl esters produces nematic behavior. All the resulting nematogens but one are the 2-methyl derivatives in which two are neopentyl esters. The smectic B phases observed for many propyl esters are not found for the isobutyl and neopentyl esters. Similarly, the smectic B and C phases of the butyl esters are eliminated by a 2-methyl substituent. On the other hand, smectic B behavior not exhibited by the pentyl esters appears in a few early homologs and smectic C behavior is thermally enhanced in some higher homologs ...

Molecular conductors based on axially substituted phthalocyanines and organic cations

Abstract The axially substituted dicyanophthalocyaninatocobalt(III) anion, [Co(Pc)(CN) 2 ] − , has been utilized for constructing molecular conductors with various closed-shell and open-shell cations. A highly conducting partially oxidized salt can be obtained from the combination with [PPh 4 ] + . Though the salt with open-shell TTF + crystallizes in the same structure, phthalocyanine is found not to be oxidized and the crystal is not conducting.

Molecular Conductors Comprised of Organic Cations and Phthalocyanines

Abstract The axially substituted dicyanophthalocyaninatocobalt(III) anion, [Co(Pc)(CN)2]−, has been utilized for constructing molecular conductors. Highly conducting partially oxidized salt can be obtained from the combination with a closed-shell cation of [PPh4]+. The crystal is composed of one-dimensional stacks of partially oxidized phthalocyanine. On the other hand, phthalocyanine is found to be not oxidized in the salts with open-shell cations such as TTF or TMTTF.

Mesomorphic Properties of Four-Ring Systems Bearing No Terminal Substituent

Abstract Temperatures of the solid-nematic and nematic-isotropic transitions have been measured for forty-eight diverse compounds bearing no terminal substituent. Four benzene rings are connected to each other by single carbon-carbon bond(s) and/or by carbonyloxy, azomethine, and azo groups. The consequence of any linking group placed centrally in a quaterphenyl molecule is a drastic suppression of the solid state stability. The nematic-isotropic transition is hardly affected by the introduction of an azo linkage and also by an azomethine one, whereas it is significantly depressed by a carbonyloxy linkage. The presence of two or three linking groups yields generally complex effects on the thermal behavior because of the marked interdependence of the effects of the linking groups. No efficiency order in promoting a nematic phase applicable to all the compounds could be established.

Two-Dimensional Molecular Arrangement in Phthalocyanine Based Conducting Crystals

Abstract Molecular arrangements in the crystals composed of the dicyanocobalt(III)phthalocyanine units, Co(Pc)(CN)2, have been examined. When the unit is closed-shell anion, the crystals contain one-dimensional arrays or isolated dimers of the Co(Pc)(CN)2 units. Two-dimensional sheets of Co(Pc)(CN)2, which are similar to those observed for the partially oxidized potassium salt, are formed when the unit is completely oxidized with existence of chloroform. A three-dimensional network of Co(Pc)(CN)2 is also obtained when the unit is oxidized with existence of water. Resultant neutral radical crystals, Co(Pc)(CN)2-2CHCl3 and Co(Pc)(CN)2.2H2O, are highly conducting.