Masato M. Ito

Why do non-symmetric dimers intercalate? The synthesis and characterisation of the α-(4-benzylidene-substituted-aniline-4′-oxy)-ω-(2-methylbutyl-4′-(4″-phenyl)benzoateoxy)alkanes

Ten new non-symmetric liquid crystal dimers belonging to the family of compounds α-(4-benzylidene-substituted-aniline-4′-oxy)-ω-(2-methylbutyl-4′-(4″-phenyl)benzoateoxy)-alkanes have been synthesised and their transitional properties characterised. The dimers contain either a hexamethylene or octamethylene spacer, while the terminal substituents on the 4-benzylideneaniline fragment are H, CH3, F, Cl and Br. The unsubstituted dimers are not liquid crystalline, while the remaining compounds exhibit enantiotropic nematic behaviour. The trends in the clearing temperatures, according to the chemical nature of the terminal substituent, are largely consistent with those established for conventional low molar mass liquid crystals. Three of the dimers also exhibit an intercalated smectic A phase, specifically the two bromo-substituted dimers and the chloro-substituted dimer containing a hexamethylene spacer. The driving force for the formation of this phase is considered to be, at least in part, the specific anisotropic interaction between the unlike mesogenic units. The absence of smectic behaviour for the isosteric methyl-substituted dimers reveals that steric factors alone cannot stabilise the intercalated smectic A phase.

α1,3-Fucosyltransferase 9 (FUT9; Fuc-TIX) preferentially fucosylates the distal GlcNAc residue of polylactosamine chain while the other four α1,3FUT members preferentially fucosylate the inner GlcNAc residue

We analyzed the substrate specificity of six human α1,3‐fucosyltransferases (α1,3FUTs) for the 2‐aminobenzamide (2AB)‐labelled polylactosamine acceptor, Galβ1‐4GlcNAcβ1‐3Galβ1‐4GlcNAcβ1‐3Galβ1‐4GlcNAc‐2AB (3LN‐2AB). FUT9 preferentially fucosylated the distal GlcNAc residue of the polylactosamine chain while the other four α1,3FUT members, FUT3, FUT4, FUT5 and FUT6, preferentially fucosylated the inner GlcNAc residue. This indicated that FUT9 exhibits more efficient activity for the synthesis of Lewis x carbohydrate epitope (Lex; CD15; stage‐specific embryonal antigen‐1 (SSEA‐1)). In contrast, the other four members synthesize more effectively the internal Lex epitope. FUT7 could not transfer a fucose to an acceptor which is non‐sialylated.

SYNTHESIS AND MESOMORPHIC PROPERTIES OF SCHIFF BASE ESTERS ORTHO-HYDROXY-PARA-ALKYLOXYBENZYLIDENE-PARA-SUBSTITUTED ANILINES

A series of new compounds o-n-hydroxy-p-n-hexadecanoyloxybenzylideneaniline and its substituted derivatives was synthesized from the esterification of palmitic acid with intermediary Schiff bases, which posssess various terminal substituents X (X = H, F, Cl, Br, OCH3, CH3, and C2H5). All compounds possess mesomorphic properties wherein compounds with X = H, F, Cl, Br, and OCH3 exhibit smectic A (SmA) phases and those with terminal substituents CH3 and C2H5 are monotropic liquid crystals showing smectic C phases (SmC). Correlation studies of the clearing temperature (Tc) of the title compounds and polarizability related to mesophase stability and molecular anisotropy are reported.

Synthesis, physical and mesomorphic properties of Schiff's base esters containing ortho‐, meta‐ and para‐substituents in benzylidene‐4′‐alkanoyloxyanilines

Three series of Schiffs base esters, 2‐hydroxy‐4‐methoxybenzylidene‐4′‐alkanoyloxyaniline, 2‐hydroxy‐3‐methoxybenzylidene‐4′‐alkanoyloxyaniline and 3‐methoxy‐4‐alkanoyloxybenzylidene‐4′‐alkanoyloxyaniline, which possess mono‐ and di‐substituted moieties at both ends of the molecules have been synthesized and their mesomorphic properties investigated along with physical characterization (elemental analysis, mass spectrometry, Fourier transform IR and high resolution NMR). The effect of lateral methoxy and polar hydroxy groups on the mesomorphism of the title compounds was studied, based on the thermal properties and textural analysis. The results indicate that compounds with the larger number of carbons in the alkyl chain prefer smectic phase formation and possess higher transition temperatures and molecular polarizability along the long axis. Further analysis shows that the greater shielding effect (through the formation of intramolecular interaction) leads to lower molecular broadening and results in higher clearing points. Increase in melting point due to the lengthening of the alkyl chain is associated with the increase in van der Waals attraction between the molecules. These compounds exhibit nematic, smectic (SmA and SmC) phases depending on the type and position of the substituents.

Synthesis and Characterization of Some New Mesogenic Schief Base Esters N-[4-(4-n-Hexadecanoyloxybenzoyloxy)-Benzylidene]-4-Substituted Anilines

Series of elongated Schiff base esters containing three aromatic rings with palmitoyl moiety as one of the terminal carbon chain and various substituents R(R=H, F, Cl, Br, OCH3, CH3, and C2H5) at the other end of molecule have been isolated, and their structures were proposed via physical measurement. The mesomorphic properties of these compounds were investigated via differential scanning calometry and polarizing optical microscopy. The thermal data indicate that all of these compounds exhibit mesomorphic properties. Although compounds with R=H, OCH3, CH3, and C2H5 show nematic phases, the remaining compounds containing halogen F, Cl, and Br are smectogenic in nature. The structural changes that result in the variation of transition temperature and the electronic polarizability of the respective molecules are discussed.

Nematic and Smectic a Phases in Ortho-Hydroxy-Para-Hexadecanoyloxbenzylidene-Para-Substituted Anilines

Four Schiff base esters containing the different substituents of R=CN, OH, SH, and NO2 were synthesized, and the physical characterization was carried out along with spectroscopic techniques (FT-IR and NMR). Thermal properties were analyzed by using differential scanning calometry (DSC), and their liquid crystal textures were observed under polarized optical microscope. All compounds thus obtained exhibit mesomorphic properties of which the alignment of molecules are inclined to either nematic, N (R=SH), or smectic, SmA (for R=CN, OH, and NO2). The unidentifiable subphases in crystal region were recorded in all compounds except that with R=OH. The presence of a lateral hydroxyl group has been claimed to contribute to the enhanced molecular ordering, leading to a higher clearing temperature.

Synthesis and mesomorphic properties of 7‐acyloxy‐3‐(4‐acyloxyphenyl)‐4H‐1‐benzopyran‐4‐one

A new homologous series of 7‐acyloxy‐3‐(4‐acyloxyphenyl)‐4H‐1‐benzopyran‐4‐ones was synthesized and characterized by elemental analysis and spectroscopic techniques along with thermal behaviour study using differential scanning calorimetry. Texture observation was performed under the polarizing optical microscope from which the derivatives were found to exhibit different molecular organizations as exemplified by various mesophases. Whilst the compounds containing butanoyloxy and hexanoyloxy groups behave as nematogens, the other compounds with heptanoyloxy and longer side chains show a SmC phase. The octadecanoyloxy derivative was the only member showing a monotropic SmC phase. The difference in phase behaviour is discussed based on the molecular structure and the presence of a lateral dipole which can be associated with the intermolecular interaction within the mesophase.

Non-Symmetric Liquid Crystal Dimers: High Thermal Stability in Nematic Phase Enhanced by Thiophene-2-Carboxylate Moiety

Series of non-symmetric liquid crystal dimers, α-(4-benzylidenechloroaniline-4′-oxy)-ω-[4-(thiophene-2-carboxyl)benzylideneaniline-4′-oxy]alkanes incorporating a thiophene-based moiety in one of the two mesogenic units have been synthesized and characterized. The nematogenic properties of the dimers were studied wherein the flexible spacers made up by n methylene units (–CH2-) ranging from n=5 to n=12. These dimers exhibit enantiotropic N phase with high thermal stability (>187.0°C). The N phase temperature range for the present homologues is found to be strongly dependent on the length and parity of the methylene spacer which connects the 4-benzylidenechloroaniline and 4-(thiophene-2-carboxyl)- benzylideneaniline mesogenic cores.

Synthesis and smectogenic properties of novel phloroglucinol-based star-shaped liquid crystals containing three peripheral alkyloxylated Schiff base arms

A series of symmetrical trimeric liquid crystalline compounds of which the molecular structure with a central core of 1,3,5-benzene attached by three rod-like mesogenic Schiff base moieties via the propylene spacers and ether linkages has successfully been synthesised and characterised by infra red and nuclear magnetic resonance spectroscopic techniques. All the star-shaped compounds in this series exhibit predominantly SmC phase except the analogue possessing terminal C8H17 group. It is apparent that the members with even parity from C10H21 to C16H33 show enantiotropic SmC phase while the member with longest terminal chain of C18H37 is inclined to monotropic smectogen. The X-ray diffraction measurements reveal that the tilted smectic layer structures of the SmC phase are confirmed to have an obvious sharp peak at small angles of 2θ ∼ 1.03°–1.48° with d-spacing values of 4.01–4.58 nm, which are corresponding to tilt angles of ∼48° in the SmC phase.

Synthesis and Anisotropic Properties of Azo-Bridged Benzothiazole-Phenyl Esters

A new series of benzothiazole-phenyl esters intersected by azo N˭N has been isolated and their structures were characterized. These compounds exhibit enantiotropic nematic phase. The transition temperatures and the enthalpy values associated with these derivatives were found to be dictated by the variation of the lengths of the flexible alkoxyl chains (OOCC n H2n+1 where n adopts even numbers from 5 to 17). A noteworthy characteristic of this series is the clearing temperatures, which decrease upon lengthening of the alkoxyl chains from n = 5 to n = 17. A descending stability associated with the nematic phase range was also observed when the carbon number in the alkyl group increased. A comparative study between the title compounds and 6-ethoxy-2-(4-alkanoxybenzylidenamino)benzothiazole shows that the present compounds favor the formation of N phase while the previously reported analogs, which contain C˭N instead of N˭N, exhibited enantiotropic N and SmC phases.