Naomi Hoshino

Mesomorphic properties of orthopalladated complexes of laterally substituted azobenzene derivatives, 2-alkoxycarbonyl-4-(4-ethoxyphenylazo)phenyl 4-methoxybenzoates

Abstract Homologous series of 2-alkoxycarbonyl-4-(4-ethoxyphenylazo)phenyl 4-methoxybenzoates (L) and their orthopalladated μ-chloro dimers (Pd2Cl2L2) have been synthesized and their thermotropic phase transition behaviour has been characterized. The ligands, L, are three-ring nematogens with their central rings substituted in the 2-position by n-alkyl chains of varied length. The thermal stability of the nematic phases decreases rapidly with increasing side chain length and then levels off as the series is ascended. In every case the mesomorphic phase appears only over a small temperature range (less than 20° C). The orthopalladated species also proved to be nematogenic. Melting and clearing points rise on the average by 87° C and 126° C, respectively, and thus the temperature ranges of the nematic phases are enlarged considerably upon metallation. In relation to the observed stabilization of the nematic phases, particularly of higher homologues, a lath-like molecular structure, in which the side chains ...

Effects of Terminal Substituents on Mesomorphic Properties: Phenyl 444-X-Substituted phenyliminomethyl)benzoate and its Isomeric Compounds

Abstract The nematic-isotropic transition temperature of phenyl 4-(4-X-substituted phenyliminomethy1)benzoate and its seven isomeric compounds carrying only one terminal substituent; i.e., methoxyl, ethoxyl, nitro, or cyano group, has been compared. The temperature is influenced not only by the terminal substituent but also by the arrangement of the linking groups and the effects of these two features are mutually dependent. The efficiency order of substituents for nematic thermal stability was found to be CN < NO2 < C2H5O < CH3O. The difference in the temperature is as large as 31 to 54°C between the cyano and methoxy derivatives and 23 to 44°C between the nitro and methoxy derivatives. The latter finding is in sharp contrast with the order CH3O < NO2, which has been generally quoted. In order to find some clue to the relationship between molecular features and mesomorphic behavior, the compounds were classified into four pairs of the isomeric compounds with the same molecular skeleton, those with a carb...

The effect of ΔΛ chirality on molecular organization in two-dimensional films of a Ru(II) complex with a mesogenic ligand

A novel amphiphilic Ru(II) complex, [Ru(acac)2L] (acac = acetylacetonato, L = 5,5′-bis(4-octylphenyloxycarbonyl)-2,2′-bipyridyl), in which L undergoes SmC, SmA and N liquid crystal phases, exhibits a remarkable chirality effect on its monolayer state: that is, a racemic mixture gives a monolayer consisting of spike-like aggregates of 1.2 nm (in height) × 50 nm (in diameter), whereas the Δ-enantiomer gives a uniform monolayer.

Thermotropic Mesophases of Benzene Derivatives with Terminally Hydroxylated Groups

Abstract Nine benzene derivatives substituted with at least one long alkyl chain in common and with various terminally hydroxylated groups have been prepared. Thermotropic meso-phases were observed in seven compounds and the hydrogen bonding of the alcoholic OH groups seems to be responsible for this behavior of novel one-ring mesogens. The X-ray diffraction patterns are consistent with a common structural model involving bimolecular layers of hydrogen bonding network separated by fully interdigitated alkyl chains.

Proton Transfer in Crystalline Aromatic Schiff Bases and Their Electronic Properties

Abstract Aromatic Schiff bases having extended II-electron systems and their charge transfer (CT) complexes have been prepared and subjected to structural, optical, and electrical conductivity studies. It is demonstrated by the X-ray crystal-lographic study that the hydroxyl protons form hydrogen bonds to the imino nitrogens, strength of which can be varied by chemical modification of the molecules. Intramolecular proton transfer takes place in solid state and is manifested in the thermochromic spectral changes.