A. I. Smirnova

Solvent-dependent mesomorphism of polycatenar silver(I) complexes in organic solvents

In this paper, the solvent-induced liquid crystal properties of a range of polycatenar complexes of silver(I) are described. The behaviour is examined in a range of solvents, where it is found that mesophases can be induced that are not present in the solvent-free materials. It is shown that in the majority of cases, the induced mesophases can be explained in terms of ideas concerning interfacial curvature and the location of added solvents, but in others, ‘chromonic’-type behaviour is found, so that the observed mesomorphism is truly a solvent-dependent phenomenon.

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...

Polycatenar Metallomesogens - From Layers to Columns and so yo Cubics

The mesomorphism of various series of polycatenar metallomesogens is described and, by considering various structure/mesomorphism arguments, a model is proposed to rationalise cubic phase formation in calamitic and polycatenar mesogens.

Lyotropic Phase Behaviour of Phthalocyanine Derivatives in Apolar Organic Solvents

Abstract Copper (II) and nickel (II) complexes of 2,3,9,10,16,17,23,24-octa(dodecyloxy)phthalocyanine (1a, 1b) and copper (II) complex of 2,9,16,23-tetra(decy1thio)phthalocyanine (1c) have been synthesized and their liquid crystalline properties have been studied. It was established, that 1a-c possess both thermotropic and lyotropic (with apolar organic solvents) mesomorphism. Lyomesomorphism exhibited by compounds can be attributed to chromonic type.

Induction of Mesomorphic Properties in Poly(propylene imine) Dendrimers and their Model Compounds

The lyotropic phase behaviour of selected dendrimers with non-mesomorphic peripheral units, i.e. decyloxybenzoyl substituted poly(propylene imine) dendrimers as well as model compounds of their main parts, i.e. decyloxybenzoyl substituted alkylamines and also derivatives of 1,4,7-triazacyclononane, has been studied. For the first time, the induction/variation of mesomorphic properties in binary systems of these dendrimers or of related model compounds with suitable organic solvents has been established.

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.

The influence of lateral fluorination and cyanation on the mesomorphism of polycatenar mesogens and the nature of the SmC phase therein

Several series of tetracatenar mesogens having different lateral substituents (–F, –CN, –CF3) on the central phenylene ring of the molecule have been synthesised and their mesomorphic behaviour investigated by polarising microscopy, differential scanning calorimetry and small-angle X-ray scattering methods. The study offers an insight into the effect of different lateral polar functions on the mesomorphism of tetracatenar mesogens and starts to try to delineate polar and steric contributions. Thus –CF3 exerts a strong steric effect that destabilises more organised mesophases (SmC, ribbon) and reduces transition temperatures. Use of a central tetrafluorophenyl unit also destabilises organised phases in common with observations made in calamitic materials, but the use of only one or two lateral fluorines has relatively little effect on transition temperatures and mesomorphism. The more polar cyano function is different in that addition of one such group reduces transition temperatures and destabilises the nematic and crystal phases, whereas the more symmetric derivative with two cyano functions shows more stable crystal and mesophases. A detailed geometrical analysis supported by X-ray diffraction data (and a dilatometry data base) leads to the proposal of a model for the SmC-to-Colr phase transformation triggered by chain-induced layer undulations in the smectic phase.

The influence of lateral apolar substituents on the mesomorphic behaviour of tetracatenar liquid crystals

Several series of new tetracatenar mesogens consisting of a five-ring aromatic core and bearing one or more apolar lateral substituents in the central benzene ring of the molecule have been synthesized and their mesomorphism is characterized by polarization microscopy, differential scanning calorimetry, and X-ray diffraction methods. Introduction of one, two, or four methyl groups into these tetracatenar mesogens destabilized columnar organization typical of the long-chain homologs, but did not suppress smectic C and nematic phases. Introduction of larger substituents did, however, suppress lamellar organization (C15H31) or mesomorphism (tert-butyl) totally.

Lyotropic mesomorphism in some thermotropic, polycatenar complexes of silver(I)

A wide range of mesophases are induced on treating polycatenar complexes of silver(I) with a wide range of organic solvents.

Induction of Mesomorphic Properties in Non-Mesogenic Octa(decyloxy) phthalocyanines

Abstract As it is well known [1, 2], non-peripheral substituted octa (alkoxy)-phthalocyanines (Pc) do not exhibit neither thermotropic nor lyotropic mesomorphism (in binary mixtures with organic solvents). In this work we induced an enantiotropic mesophase due to charge-transfer (CT) interactions in mixtures of PC derivatives I-III (viscous or oil-like liquids) with a strong electron acceptor 2,4,7-trinitro-9-fluorenone (TNF). Decreasing of number and length of substituents and modification of chemical structure of phthalocyanine macrocycle by introduction of four sulfur atoms (compound IV) resulted in crystallinity of this compound. In contact preparation of IV with TNF a wide area of CT-complex showing the monotropic mesomorphic phase is found out. All above mentioned CT-complexes do not form any lyomesophases in binary mixtures with number of organic solvents.