Tailoring the physical properties of some high birefringence isothiocyanato-based liquid crystals

This paper describes the synthesis and characterization of several liquid crystal compounds having a tolane or terphenyl core structure and a high polarizability, isothiocyanato (NCS), terminal group. The synthesized compounds have high optical birefringerce (0.35 and 0.52), the highest being exhibited by the olefin-tolanes. Several eutectic mixtures are formulated and show improved properties over the single compounds, such as a broad nematic range, low melting temperature and relatively high clearing point. The birefringence of these mixtures is in the range 0.35-0.37. UV, viscosity and electro-optical measurements of the synthesized compounds are also reported. Dipole moment and polarizability calculations were made using CS-MOPAC and Hyperchem software computational programmes.     

synthesis, phase transitions and optical properties of novel tetrathiafulvalene derivatives with extremely high molecular polarizabilities

The synthesis of novel unsymmetrically-substituted tetrathiafulvalene derivatives based on lithiation procedures is described. The disubstituted derivatives were synthesized as 1:1 cis/trans-isomeric mixtures, the compositions of which were established by ¹H NMR and ¹³C NMR spectroscopy. The transition temperatures, refractive indices, birefringence, polarizability and order parameter of each of the mixtures were determined and the values are discussed in comparison with analogous compounds with the tetrathiafulvalene unit replaced by a 1,4-phenylene group. In addition, we describe the synthesis of a number of monosubstituted tetrathiafulvalene derivatives and their associated thermal properties. The isomeric compounds presented in this paper have exceptionally large values of polarizability anisotropy, as compared with their phenyl-containing counterparts.     

synthesis,phase transitions and optical properties of novel tetrathiafulvalene derivatives with extremely high molecular polarizabilities

The synthesis of novel unsymmetrically-substituted tetrathiafulvalene derivatives based on lithiation procedures is described. The disubstituted derivatives were synthesized as 1:1 cis/trans-isomeric mixtures, the compositions of which were established by ¹H NMR and ¹³C NMR spectroscopy. The transition temperatures, refractive indices, birefringence, polarizability and order parameter of each of the mixtures were determined and the values are discussed in comparison with analogous compounds with the tetrathiafulvalene unit replaced by a 1,4-phenylene group. In addition, we describe the synthesis of a number of monosubstituted tetrathiafulvalene derivatives and their associated thermal properties. The isomeric compounds presented in this paper have exceptionally large values of polarizability anisotropy, as compared with their phenyl-containing counterparts.     

The Importance of Polarity/Polarizability Interaction on the Acidity Behavior of 9,10-Anthraquinone and 9-Anthrone Derivatives in Methanol-Water Mixed Solvents Using Target Factor Analysis and QSPR Approaches

The influence of solvent properties on acidity constants of some newly synthesized 9,10-anthraquinone and 9-anthrone derivatives was studied in methanol-water mixtures in a composition range of 0.57 to 1.0 methanol mole fraction. The model was established by using both multiple linear regression and target factor analysis. Both methods revealed that the solvent polarity/polarizability parameter ^* is a major factor in controlling the acidity behavior of the anthraquinones and anthrones studied in binary methanol-water mixed solvents. A QSPR study was conducted to drive the relationships between the ^* coefficient s and the polarity/polarizability of molecules. Both dipole moment and polarizability were found to have a linear relationship with s. The results confirm that, in the dipolar protic solvents used, the dipole-dipole interaction (for neutral molecules) and the ion-dipole interaction (for ionized molecules) are the major factors controlling the acidity behavior of these compounds.     

Selectivity of stationary phases in reversed-phase liquid chromatography based on the dispersion interactions

Selectivity of 15 stationary phases was examined, either commercially available or synthesized in-house. The highest selectivity factors were observed for solute molecules having different polarizability on the 3-(pentabromobenzyloxy)propyl phase (PBB), followed by the 2-(1-pyrenyl)ethyl phase (PYE). Selectivity of fluoroalkane 4,4-di(trifluoromethyl)-5,5,6,6,7,7,7-heptafluoroheptyl (F13C9) phase is lowest among all phases for all compounds except for fluorinated ones. Aliphatic octyl (C8) and octadecyl (C18) phases demonstrated considerable selectivity, especially for alkyl compounds. While PBB showed much greater preference for compounds with high polarizability containing heavy atoms than C18 phase, F13C9 phase showed the exactly opposite tendency. These three stationary phases can offer widely different selectivity that can be utilized when one stationary phase fails to provide separation for certain mixtures. The retention and selectivity of solutes in reversed-phase liquid chromatography is related to the mobile phase and the stationary phase effects. The mobile phase effect, related to the hydrophobic cavity formation around non-polar solutes, is assumed to have a dominant effect on retention upon aliphatic stationary phases such as C8, C18. In a common mobile phase significant stationary phase effect can be attributed to dispersion interaction. Highly dispersive stationary phases such as PBB and PYE retain solutes to a significant extent by (attractive) dispersion interaction with the stationary phase ligands, especially for highly dispersive solutes containing aromatic functionality and/or heavy atoms. The contribution of dispersion interaction is shown to be much less on C18 or C8 phases and was even disadvantageous on F13C9 phase. Structural properties of stationary phases are analyzed and confirmed by means of quantitative structure-chromatographic retention (QSRR) study.     

Linear solvation energy relationships of anionic dimeric surfactants in micellar electrokinetic chromatography II. Effect of the length of a hydrophilic spacer

Anionic dimeric surfactants with hydrophilic spacers containing two to six oxygen atoms were synthesized and applied as pseudostationary phases in micellar electrokinetic chromatography. Their selectivity was determined via linear solvation energy relationships. There were no differences in cohesiveness, polarizability or dipolarity with increasing spacer length, but there was a clear trend in increasing hydrogen bond accepting ability, and a concomitant decrease in hydrogen bond donating ability. The different selectivity of these dimeric surfactants compared to sodium dodecylsulfate can be useful for optimizing separations of mixtures of solutes for which these types of interactions are important. Their critical micelle concentrations were in the range of 0.2-0.3mM, except for the surfactant with the shortest spacer (<0.03 mM), and are much lower than those of conventional surfactants used in micellar electrokinetic chromatography.     

Unusual solvatochromism within 1-butyl-3-methylimidazolium hexafluorophosphate + poly(ethylene glycol) mixtures

Hybrid "green" solvent systems composed of room-temperature ionic liquids (ILs) and poly(ethylene glycols) (PEGs) may have enormous future potential. Solvatochromic absorbance probe behavior is used to assess the physicochemical properties of the mixture composed of IL 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF(6)]) and PEG (average molecular weights of 200, 400, 600, and 1500) at ambient conditions. Lowest energy intramolecular charge-transfer absorbance maxima of a betaine dye, i.e., E(T)(N), indicates the dipolarity/polarizability and/or hydrogen-bond donating (HBD) acidity of the [bmim][PF 6] + PEG mixtures to be even higher than that of neat [bmim][PF(6)], the solution component with higher dipolarity/polarizability and/or HBD acidity. Dipolarity/polarizability (pi*) obtained separately from the electronic absorbance response of probe N, N-diethyl-4-nitroaniline shows a trend similar to E(T)(N ) thus confirming the unusually high dipolarity/polarizability of the [bmim][PF(6)] + PEG mixtures. Similar to E(T)(N ) and pi*, the HBD acidity (alpha) of [bmim][PF(6)] + PEG mixtures is also observed to be anomalously high. Contrary to what is observed for E(T)(N ), pi*, and alpha, the hydrogen-bond accepting (HBA) basicity (beta) of the [bmim][PF(6)] + PEG mixtures is observed to be lower than that predicted from ideal additive behavior indicating diminished HBA basicity of the mixture as compared to its neat components. A four-parameter simplified combined nearly ideal binary solvent/Redlich-Kister (CNIBS/R-K) equation is shown to satisfactorily predict the solvatochromic parameters within [bmim][PF(6)] + PEG mixtures. It is demonstrated that [bmim][PF(6)] + PEG mixtures possess physicochemical properties that are superior to those of either the neat IL or the neat PEG.     

偶氮香豆素化合物的二阶非线性极化率

测定了一系列偶氮香豆素化合物的紫外吸收波长(λ_a)、摩尔吸光系数(ε)和最大荧光发射波长(λ_e)的数据,并用溶致变色法测算了它们的二阶非线性极化率(β_xxx).结果表明,所测定的化合物在溶液状态下表现出较强的二阶非线性极化特性.     

Schiff bases of indoline-2,3-dione (isatin) with potential antiproliferative activity

ABSTRACT: BACKGROUND: Cancer is one of the most dreaded diseases and it is a leading cause of mankind death worldwide. Recent reports documented a remarkable antiproliferative activity of isatin nucleus against various cancer cell lines. The current work describes the antiproliferative activity of Schiff bases of combinatorial mixtures of the isatin derivatives M1-M22 as well as the individual compounds 1-11(A-K) of these combinatorial mixtures. RESULTS: The designed combinatorial library composed from eleven hydrazides A-K and eleven isatin derivatives 1-11 has been synthesized to formally generate 22 mixtures, M1-M22 of 121 Schiff bases, and their antiproliferative activity against K562 chronic myelogenous leukemia cells was evaluated. The indexed method of analysis of the prepared library was applied to elucidate the active components in the tested mixtures M1-M22. The predictions from the crossing procedure was validated through evaluation of the antiproliferative activity of individual compounds 1-11(A-K) of the library. Individual compounds 1-11(A-K) were also evaluated against the non-tumorigenic MCF-12A cell line to investigate their selectivity. A pharmacophore model was developed to further optimize the antiproliferative activity among this series of compounds. CONCLUSIONS: Variable antiproliferative activity was revealed with the investigated mixtures M1-M22 and the individual compounds 1-11(A-K). Most of the tested mixtures and several individual Schiff bases displayed high potency with IC50 values in the low micromolar range. A considerable selectivity of some individual compounds to the tumorigenic K562 cell line compared with the non-tumorigenic MCF-12A cell line was observed as indicated by their selectivity index (SI).     

Intermolecular polarizability dynamics of aqueous formamide liquid mixtures studied by molecular dynamics simulations

A molecular dynamics simulation study is presented for the relaxation of the polarizability anisotropy in liquid mixtures of formamide and water, using a dipolar induction scheme that involves the intrinsic polarizability and first hyperpolarizability tensors of the molecules, and the dipole-quadrupole polarizability of water species. The long time diffusive decay of the collective polarizability anisotropy correlations exhibits a substantial slowing down as the formamide mole fraction increases in the mixture. The diffusive times for the polarizability relaxation obtained from the authors' simulations are in good agreement with optical Kerr effect experimental data, and they are found to correlate nearly linearly with the estimated mean lifetimes of the hydrogen bonds within the mixture, suggesting that the relaxation of the hydrogen bond network is responsible to some extent for the collective relaxation of the polarizability anisotropy of the mixture. The short time behavior of the polarizability anisotropy relaxation was investigated by computing the nuclear response function, R(t), which is very rapidly dominated by the formamide contribution as it is added to water, due to the much larger polarizability anisotropy of formamide molecules compared to that of water. Several contributions to the Raman spectrum were also analyzed as a function of composition, and the dynamical origin of the different bands was determined.     

Microwave-assisted solution-phase synthesis and DART-mass spectrometric monitoring of a combinatorial library of indolin-2,3-dione schiff bases with potential antimycobacterial activity

A combinatorial library composed of eleven hydrazides A-K and eleven indolin-1,2-dione derivatives 1-11 has been designed to formally generate sublibraries of 22 mixtures, M(1)-M(22) comprising of 121 Schiff bases, A-K(1-11). The designed library has been synthesized by the solution-phase method and microwave-assisted synthetic techniques. The formation of individual compounds of each mixture was confirmed by Direct Analysis in Real Time (DART) as ionization technique connected to an Ion Trap as a mass detector. The synthesized mixtures were evaluated for their antimycobacterial activity against four Mycobacterium strains; M. intercellulari, M. xenopi, M. cheleneoi and M. smegmatis. Variable antimycobacterial activity was revealed with the investigated mixtures and maximum activity was shown by M(8), M(10), M(11), and M(15) with MIC values of 1.5, 3.1, 6.2 and 0.09 μg/mL, respectively. Application of the indexed method of analysis on these active mixtures revealed that compounds D(8), D(10) and D(11) may contribute to the activity of the tested mixtures.     

Synthesis and mesomorphic properties of cyano derivatives of 2-(4-carbohydroxy-3-halogenphenyl)-5-alkyl-1,3,2-dioxaborinanes

Cyano derivatives of 2-(4-carbohydroxy-3-halogenphenyl)-5-alkyl-1,3,2-dioxaborinane have been synthesized. These compounds are characterized by low nematic-isotropic transition temperatures and a high positive dielectric anisotropy; they are promising for use in liquid-crystalline mixtures intended for high information electrooptic display devices.     

Novel liquid crystal mixtures for a surface-stabilized ferroelectric LCD

We synthesized novel fluorine-substituted chiral compounds having a fluorine atom at an asymmetric carbon and a difluorinated biphenyl ring as a core of a liquid crystal molecule by means of an original method. The ferroelectric mixtures were obtained by mixing the chiral compounds with the non-chiral liquid crystal mixture with a wide SmC temperature range between 29 C (crystallized) and 78 C. They show a large P s greater than 10 nC cm -2 at 5 wt% of the chiral compound. Two types of cell, called 'parallel' and 'antiparallel', were fabricated according to the relative direction of the rubbing direction on the substrates. The parallel cells filled with the FLC mixtures show the usual bistable SSFLC (surface-stabilized ferroelectric liquid crystal). The fast response time of 60mus (22V pp pulse width 250mus, at room temperature) was obtained. The apparent cone angle was 45.2 in the switching state and 40.5 in the memory state. On the other hand, the antiparallel cells show an unusual monostable behaviour, i.e. the director falls back to the original configuration when the applied voltage is switched off. The surface-stabilized monostable cells show very attractive characteristics for application for a TFT-active matrix LCD; a high contrast of 81 :1, a fast response time (of the order of 1ms), and an analogue-grey scale with excellent linearity within the low voltage range below 4 V.     

Halide affinity for the water-air interface in aqueous solutions of mixtures of sodium salts

The water-air interface plays a critical role in many physical and chemical processes of the Earth's atmosphere. In particular, heavy halide ions are strongly involved in processes of fundamental importance in determining the prevalence of many atmospheric components through heterogeneous reactions at the water-air interface. In this work, molecular dynamics simulations are used to study the halide enhancements at the water-air interface in the case of mixtures of Cl(-), Br(-), and I(-) ions. The results show a pattern of enhancement directly correlated to the anion polarizability. This effect is explained in terms of the charge distribution across the slab resembling an electrical double layer. As a result, the anions with higher polarizability lower the system's potential energy by enhancing their presence at the interface.     

New steroid α,β-unsaturated ketones as chiral components of induced cholesteric liquid crystal systems

New (E)-16-arylidene derivatives of 3β-hydroxyandrost-5-en-17-one and their acetates containing different substituents in the arylidene fragment were synthesized. The ability of the synthesized chiral compounds to induce helical supramolecular ordering (their helical twisting power) upon the introduction into the nematic liquid crystal (LC) 4-cyano-4′-pentylbiphenyl (5CB) and into multicomponent mixtures E63 and LC-1289 characterized by a wide mesophase interval. The dependence of the helical twisting power of the studied chiral additives (CAd) on their molecular structure was analyzed. The highest helical twisting power (44.6–67.1 μm⁻¹) was revealed for the synthesized acetates. It was found that the composites based on LC-1289 and E63 containing the studied CAd in very low concentrations (≤10–11 mol.%) have selective light reflection in the visible spectral region. The helical twisting power of the studied α,β-unsaturated ketones is determined by the combined influence of the anisotropy of polarizability of CAd molecules and specific features of their molecular shape.     

Molecular interactions in 1-pentanol +2-methyl-2-butanol mixtures: Static dielectric constant,viscosity and refractive index investigations at 5, 25 and 45°C

Static dielectric constants, refractive indices and viscosities of 1-pentanol +2-methyl-2-butanol mixtures were measured at 5, 25 and 45°C. The results show that the mixing of the two isomers modifies the polarizability and the resistence of viscous flow of the system depending on the composition and temperature. Short range intermolecular interactions producing hetero-alcohol open dimers are considered.     

Synthesis and mesomorphic properties of cyano derivatives of 2-(4-carbohydroxy-3-halogenphenyl)-5-alkyl-1,3,2-dioxaborinanes

Abstract

Cyano derivatives of 2-(4-carbohydroxy-3-halogenphenyl)-5-alkyl-1,3,2-dioxaborinane have been synthesized. These compounds are characterized by low nematic-isotropic transition temperatures and a high positive dielectric anisotropy; they are promising for use in liquid-crystalline mixtures intended for high information electrooptic display devices.