N. V. Usol'tseva

Lyotropic phase behaviour of disc-shaped tetra-palladium organyls in apolar organic solvents [1]

Abstract The lyomesomorphic behaviour in apolar organic solvents of members of two series 1 and 2 of disc-shaped palladium organyls—the syntheses of four of them are new (1d, f and 2a, e) and are described here—each carrying twelve long lipophilic chains have been studied. Their lyomesomorphism appeared to be complex and has been observed here for the first time with metal organyls. As can be seen by polarizing microscopy, most of the binary mixtures investigated here exhibit nematic properties. For two members of series 1—the chloro-bridged 1b and its bromo-analogue 1c—there is even evidence for the existence of two different nematic lyomesophases side by side showing reversible transitions between them. In ternary systems, i.e. after the addition of 2,4,7-trinitrofluorenone (TNF, a strong electron acceptor), the nematic phases are stabilized, suggesting that their mesophase structures are made up by columns with intercalated TNF molecules (charge transfer complex formation). Influences of structural fea...

The first case of a lyotropic twisted nematic (N∗) phase induced by a chiral charge transfer complex [1]

Abstract The disc-shaped tetra-palladium organyl 1 forms optically active charge transfer complexes in equimolar mixtures with the enantiomers of the π-acid electron acceptor 2, (+)- or (−)-TAPA, exhibiting lyotropic cholesteric nematic properties in apolar organic solvents. These ternary systems are the first examples in which such a lyomesophase has been induced by charge transfer interactions.

On the nematic-nematic phase transition in mixtures composed of sheet-shaped palladium organyls and apolar organic solvents

Abstract The three sheet-shaped palladium organyls 1a-c exhibit lyotropic nematic properties in apolar organic solvents. The occurrence of two nematic lyomesophases was verified by the investigation of the orientational properties of these liquid crystalline systems. In cells with obliquely deposited SiO x layers, the director of the high temperature phase N2 is aligned in a homogeneous, planar manner. In the low temperature phase N1, a different orientational pattern is observed. The specific pattern type depends on the deposition conditions of the SiO x layers. In samples homeotropically aligned in the N2 phase, the director is tilted away from the cell normal after the transition into the N1 phase. These changes of orientation are reversible. The experimental observations presented here support our proposed model for the structural change at the nematic-nematic phase transition.

The Molecular and Supramolecular Structure of Metalloorganic Lyotropic Mesogens

Abstract On the basis of data in literature and those obtained from our experiments we have analysed the influence of metal in the structure of rod-like and discoid amphiphilic molecules on their lyotropic mesomorphism.

Synthesis, mesomorphism and electrochemical properties of tetrasubstituted zinc and copper phthalocyanines

We describe the synthesis of highly soluble, tetrasubstituted zinc and copper phthalocyanines exhibiting liquid crystalline properties. These compounds were characterized using elemental analysis, MS, 1H-NMR, FTIR and UV-Vis absorption spectroscopy. The liquid crystalline properties of phthalocyanines (Pcs) were studied by polarizing optical microscopy and differential scanning calorimetry. All of the four compounds exhibit thermotropic columnar mesophases and two of them show clear hexagonal ordering. Additionally, these Pcs display lyotropic behaviour. The clearing temperatures lie above 300 °C and on cooling down the mesophase can be “frozen” into a glassy state. The cyclic voltammetry studies of these phthalocyanines show electrochemical stability and reversible redox behaviour. The Pcs without any azo groups in the ligands exhibit both reversible oxidation and reduction, whereas those with azo groups show only reversible reduction steps. The low HOMO energy values of about 5 eV as calculated from oxidation potential make these compounds interesting as p-type organic semiconductors for electro-optical applications.

Mesomorphism and Glass Formation of Phthalocyanine Metal Complexes with Bulky Substituents

This paper deals with the synthesis of phthalocyanine complexes, containing four oligo(oxyethylene)-, oxybenzene-, esther of p-oxybenzoic acid or p-oxyazobenzene side chains terminated by a bulky trityl substituent. Their purity was established by column chromatography and by satisfactory elemental analysis. The structures of resultant phthalocyanines were characterized by nuclear magnetic resonance (NMR), fast atom bombardment mass spectroscopy (FAB-MS), ultraviolet-visible (UV-VIS) and infrared (IR) spectroscopy and their phase transitions were studied by polarizing optical microscopy. Some of these complexes exhibit enantiotropic mesomorphic properties and transition into glass state on cooling. The glass appearance is influenced not only by side chains’ structure, but also by the nature of metal.

Comparative lyotropy study of homologous hexaesters of hexahydroxy-benzene and -cyclohexane (scyllitol) in linear and cyclic hydrocarbons: microsegregation and mesophase formation of discotics [1]

The investigation addressed in the title was carried out on a total of 17 members of the two disc-shaped series 1 or 2 of radial hexaesters differing only in their cyclic C6-core units. Their lyotropic behaviour appeared to be dependent on the intracolumnar order of stacking of the respective hexaester molecules. With linear alkanes in mixtures with the phenylene centred hexaesters (series 1 derived from hexahydroxybenzene) no lyomesomorphism occurs, whereas with most of the cyclohexane centred analogues (series 2, scyllitol derivatives) even two lyomesophases were observed: a hexagonal type and, in 49 cases, a nematic columnar (induced) phase. Here, the lyotropy demonstrates its dependence on the length of chains both of the alkanoyl groups of 2 and the solvent (the linear alkanes) used. In the case of the selected cyclic solvents, three factors proved to govern the lyotropic mesomorphism of all these disc-like hexaesters: (1) their degree of saturation, (2) their molecular size/volume, and (3) their ste...

Influence of molecular structure peculiarities of phthalocyanine derivatives on their supramolecular organization and properties in the bulk and thin films

In order to study the influence of molecular structure peculiarities on supramolecular organization and properties in the bulk and thin films of discotic mesogens six new mix-substituted phthalocyanine derivatives with 3,6-dioctyloxyphthalonitrile and 3,4,5,6-tetrachlorophthalonitrile fragments were synthesized. Temperatures of phase transitions, types of mesophase and their dependence on molecule structure, chemical nature, position and ratio of different substituents as well as presence of holmium in the metal complexes were analyzed. The behavior of the studied molecules on the boundary between water and air was investigated and the peculiarity of supramolecular organization in floating layers as well as in thin films was determined. Quenching of luminescence in solutions of the studied compounds in the presence of fullerene C60 was determined, thus giving prospects for application of these compounds as sensors for fullerene microquantities.

Synthesis and Induction of Mesomorphic Properties of Tetrabenzoporphine Derivatives

Zinc complexes of meso-alkyl-substituted tetrabenzoporphines and their aza-derivatives have been synthesized using the interaction of phthalimide or its derivatives with zinc salts of the carboxylic acids. The porphyrin-ligands were obtained on the basis of the above mentioned compounds. The spectral and mesomorphic properties of the synthesized compounds were studied.

Erratum to: “Nucleophilic Substitution in 4-Bromo-5-nitrophthalodinitrile: XI. Preparation, Properties, and Prediction of Mesomorphism in Mixed-Substituted Phthalocyanines Containing Aryloxy and Benzotriazole Fragments”

Stepwise nucleophilic substitution of bromine and nitro group in 4-bromo-5-nitrophthalodinitrile has led to a series of phthalonitriles containing benzotriazole and aryloxy fragments; basing on them, the mixed-substituted phthalocyanines have been prepared. The spectral properties of products have been studied. According to simulation of columnar mesomorphism only one of the products is not capable of mesomorphism characteristic of discotic mesogens; the result has been confirmed with the experiment.