3-(2-Cyanoethyl)-6-aryl- or 6-(trans-4-alkylcyclohexyl)cyclohex-2-enones: synthesis,transformations and mesomorphic properties

The synthesis and chemical transformations of 3-(2-cyanoethyl)-6-aryl- or 6-(trans-4-alkylcyclohexyl)cyclohex-2-enones into nematic and smectic liquid crystalline compounds are discussed. These 3,6-disubstituted cyclohex-2-enones were prepared by the condensation of appropriate Mannich salts or trans-4-alkylcyclohexyl 2-bromoethyl ketones with ethyl 2-(2-cyanoethyl)acetoacetate.     

New liquid crystalline cyclohexene and cyclohexane derivatives and compositions based upon them

The synthesis and chemical transformations of 3,6-disubstituted cyclohex-2-enones into new liquid crystalline cyclohexene and cyclohexane derivatives are discussed. 3,6-Disubstituted cyclohex-2-enones have been synthesized by the condensation of appropriate 2-bromoethyl ketones or Mannich salts with 2-[2-(trans -4-alkylcyclohexyl)ethyl]acetoacetic or 2-[2-(4-substituted phenyl)ethyl]acetoacetic esters.     

Synthesis and mesomorphic properties of four-ring liquid crystals containing 2,3-difluorophenyl and 1,3-dioxane units

Two series of novel liquid crystalline materials were synthesized: 2-(2,3-difluoro-4-alkoxyphenyl)-5-[4-(4-alkylcyclohexyl)phenyl]-1,3-dioxanes (A _m-n and 2-(2,3-difluoro-4-alkylphenyl)-5-[4-(4-alkylcyclohexyl)phenyl]-1,3-dioxanes (B _m-n ). Their mesmorphic properties were characterized by polarizing optical microscopy and differential scanning calorimetry. All these compounds exhibit broad mesomorphic phases, and most of them show wide smectic C phases and the phase sequence Cr-SmC-SmA-N-I. The relationship between properties and chemical structures is discussed in detail.     

Sulfur-linked cyanobiphenyl-based liquid crystal dimers and the twist-bend nematic phase

ABSTRACT

The synthesis and characterisation of two series of cyanobiphenyl-based liquid crystal dimers containing sulfur links between the spacer and mesogenic units, the 4?-[1,ω-alkanediylbis(thio)]bis-[1,1?-biphenyl]-4-carbonitriles (CBSnSCB), and 4?-({ω-[(4?-cyano[1,1?-biphenyl]-4-yl)oxy]alkyl}thio)[1,1?-biphenyl]-4-carbonitriles (CBSnOCB) are described. The odd members of both series show twist-bend nematic and nematic phases, whereas the even members exhibit only the nematic phase. An analogous cyanoterphenyl-based dimer, 3⁴-{6-[(4?-cyano[1,1?-biphenyl]-4-yl)thio]-hexyl}[1¹,2¹:2⁴,3¹-terphenyl]-1⁴-carbonitrile (CT6SCB), is also reported and shows enantiotropic N_TB and N phases. The transitional properties of these dimers are discussed in terms of molecular curvature, flexibility and biaxiality. The same molecular factors also influence the birefringence of nematic phases. Resonant X-ray scattering studies of the twist-bend nematic phase at both the carbon and sulfur absorption edges were performed, which allowed for the determination of critical behaviour of the helical pitch at the transition to the nematic phase, the behaviour was found to be independent of molecular structure. It was also observed that despite the different molecular bending angle and flexibility, in all compounds the helical pitch length far from the N-N_TB transition corresponds to 4 longitudinal molecular distances.     

3-Aryl- or 3-(trans-4-alkylcyclohexyl)- 6-arylcyclohex-2-enones: synthesis,transformations and mesomorphic properties

The synthesis and chemical transformations of 3-aryl- or 3-(trans-4-alkylcyclohexyl)- 6-arylcyclohex-2-enones into liquid crystalline compounds are discussed. These 3,6-disubstituted cyclohex-2-enones were prepared by the condensation of appropriate Mannich salts or trans-4-alkylcyclohexyl 2-bromoethyl ketones with 4-substituted benzyl methyl ketones.     

New isothiocyanatotolane liquid crystals with terminal but-3-enyl substitute

Four kinds of new but-3-enyl-based isothiocyanate liquid crystals composed of tolane core and but-3-enyl terminal group (A1–A4) were synthesised via seven step reactions based on 2-(4-bromophenethyl)-1,3-dioxolane, and four n-butyl analogues B1–B4 as comparison structures were also prepared. The mesomorphic properties and physical properties of the compounds were investigated. Single fluorinated compounds A2 and A3 exhibit monotropic nematic phase, and they have lower melting enthalpy and higher clearing points than those of the comparison compounds B2 and B3. The non-fluoro-substituted compound A1 and difluorinated compound A4 exhibit no nematic phase. Replacement of n-butyl chain by but-3-enyl as terminal group is enabled to increase birefringence (Δn ~ 0.394–0.430) and reduce rotational viscosity. These isothiocyanatotolanes with terminal but-3-enyl substitution have potential application for high birefringence mixtures.     

Synthesis and reactivity with M(II) (M=Co and Cu) chloride of 1-[(2-carboxyethyl)benzene]-3-[benzothiazole]triazene

Reaction of ethyl anthranilate, sodium nitrite, and 2-aminobenzothiazole produces a new triazenide compound, 1-[(2-carboxyethyl)benzene]-3-[benzothiazole]triazene (HL), which has been characterized by X-ray crystallography and NMR spectrum. In the presence of Et₃N, reaction of HL and CuCl₂?·?2H₂O or CoCl₂?·?6H₂O in THF/methanol affords a tetranuclear copper(II) complex [Cu₄L₄(µ-OMe)₄]?·?4THF (1) and a cobalt(III) complex [CoL′₃] (2) (L′ is 1-[benzothiazole] triazene ion), accompanied by C–N bond cleavage of HL. They are characterized by X-ray crystallography and magnetic susceptibility measurement. Magnetic studies indicate significant antiferromagnetic coupling between the copper(II) centers for 1. The value obtained for the coupling constant J is ?585?cm^?1.     

DNA-binding and cleavage activity of polypyridyl ruthenium(II) complexes

Polypyridyl ruthenium(II) complexes [Ru^II(3-bptpy)(dmphen)Cl]ClO₄ (1), [Ru^II(3-cptpy)(dmphen)Cl]ClO₄ (2), [Ru^II(2-tptpy)(dmphen)Cl]ClO₄ (3), and [Ru^II(9-atpy)(dmphen)Cl]ClO₄ (4) {where 3-bptpy?=?4′-(3-bromophenyl)-2,2′:6′,2″-terpyridine, 3-cptpy?=?4′-(3-chlorophenyl)-2,2′:6′,2″-terpyridine, 2-tptpy?=?4′-(2-thiophenyl)-2,2′:6′,2″-terpyridine, 9-atpy?=?4′-(9-anthryl)-2,2′:6′,2″-terpyridine, dmphen?=?2,9-dimethyl-1,10-phenanthroline} have been synthesized and characterized. The DNA-binding properties of the complexes with Herring Sperm DNA have been investigated by absorption titration and viscosity measurements. The ability of complexes to break the pUC19 DNA has been checked by gel electrophoresis. The experimental results suggest that all the complexes bind DNA via partial intercalation. The results also show that the order of DNA-binding affinities of the complexes is 4?<?3?<?2?<?1, confirming that planarity of the ligand in a complex is very important for DNA-binding.     

Synthesis and mesomorphic properties of the homologous series of 4′-bromophenyl 4′'-[(4-n-alkoxy-2,3,5,6 tetrafluorophenyl)ethynyl]benzoates

Abstract

A homologous series of 4′-bromophenyl 4′'-[(4-n-alkoxy-2,3,5,6-tetrafluoro-phenyl)ethynyl]benzoates has been synthesized. The transition temperatures were studied by polarizing optical microscopy. The compounds exhibit nematic and smectic A phases.     

Synthesis and mesomorphic properties of four-ring fluorinated liquid crystals with trifluoromethyl group

The discovery of nematic phase in 3-fluoro-4-trifluoromethyl-4?-(4?-alkyl [trans, trans-1,1?-bicyclohexyl]-4-yl) 1,1?-biphenyls (n = 2, 3, 4, 5) is an accidental affair. A convenient method was used for the synthesis of these target compounds. After the preparation of the intermediate with trifluomethyl group, the target compounds were synthesised by Suzuki cross-coupling reaction. Then, these phase transition temperatures were measured by polarising textural observation, which confirmed the existence of single nematic phase. These temperatures were also measured by differential scanning calorimetry, which showed that the clearing point of compound (n = 3) is 267℃. The possible mechanism of occurrence of unique nematic phase was discussed on the basis of the principles of fluorine chemistry.     

Dielectric studies of liquid crystals under high pressure III. Low frequency relaxation process in 4-(trans-4′-n-hexylcyclohexyl)isothiocyanato benzene

Abstract

Dielectric studies of 4-(trans-4′-n-hexylcyclohexyl) isothiocyanatobenzene (6CHBT) were performed in the pressure range 0·1–150 MPa, the frequency range 1 kHz–13 MHz and the temperature range 295–325 K. The temperature and pressure dependencies of the static permittivity ?_0∥ and of the relaxation time τ_∥ are analysed and compared with the analogous data obtained recently for 4-n-pentyl-4′-cyanobiphenyl (5CB) (Parts I and II of this series). Marked differences in the dielectric properties of the nematic phases of the two substances are observed. They are interpreted as a result of varying degrees of molecular association in particular compounds. It is concluded that in the nematic phase of 6CHBT dipole–dipole correlations do not exist or are very weak, whereas for 5CB they are easily broken by a relatively low pressure.     

Synthese und flüssigkristalline Eigenschaften 2,6-disubstituierter Naphthaline

Synthesis and Liquid-Crystal Properties of 2,6-Disubstituted Naphthalene Derivatives The syntheses and the mesomorphic properties of a series of novel 2,6-disubstituted naphthalenes are described. 4-[6-(n-Alkyl)-2-naphthyl]benzonitriles 5 and 4-[6-(n-Alkoxy)-2-naphthyl]benzonitriles 8 exhibit widerange nematic mesophases. 6,6′-Di(n-alkyl)-2,2′-binaphthyls 6 have been isolated as by-products from the reaction mixtures of 5 . Some of these novel compounds have polymorphic properties. The esters 13 and 15 of 4-(6-hydroxy-2-naphthyl)benzonitrile show enhanced mesophase stabilities which reach maximum values in the series of α, β-unsaturated esters 15 . The 4-(n-pentyl)benzoate 14 of the same (hydroxynaphthyl)benzonitrile has a melting point of 125° and a clearing point of > 310°. This particular derivative belongs to those liquid-crystalline compounds having the broadest purely nematic-phase range. In addition, (RS)-4-(2-pentyl-6-chromanyl)benzonitrile ( 20 ) and three compounds with two and four laterally arranged CN groups at the bicyclo[2.2.2]octene, bicyclo[2.2.2]octadiene, and the phenyl-ring systems 31 – 33 were synthesized. Only 20 shows mesomorphic properties.     

Cobalt(II) complexes with pyridine and 5-[(E)-2-(aryl)-1-diazenyl]-quinolin-8-olates: synthesis,electrochemistry and X-ray structural characterization

Abstract

Nine new cobalt(II) compounds, trans-[Co(L^PAQ)₂(Py)₂] (1), trans-[Co(L^PAQ)₂(3-MePy)₂] (2), trans-[Co(L^MeAQ)₂(Py)₂] (3), trans-[Co(L^OMeAQ)₂(Py)₂] (4), trans-[Co(L^OEtAQ)₂(Py)₂]·2(H₂O) (5), trans-[Co(L^CAQ)₂(Py)₂] (6), trans-[Co(L^BAQ)₂(Py)₂] (7), cis-[Co(L^BAQ)₂(3-MePy)₂] (8a) and trans-[Co(L^BAQ)₂(3-MePy)₂]·2(3-MePy) (8b) (primary ligand: L^XAQ?=?substituted 5-[(E)-2-(aryl)-1-diazenyl]quinolin-8-olate; secondary ligands: Py?=?pyridine, 3-MePy = 3-methylpyridine), have been synthesized and characterized by elemental analysis, IR and UV-vis spectroscopy. Magnetic measurements of the cobalt compounds were performed in solution by ¹H NMR spectroscopy using the Evans’ method while their redox properties were studied by cyclic voltammetry. Single-crystal X-ray diffraction analysis of the compounds revealed their octahedral geometries and trans configuration, except for 8a, which has a cis configuration. Intermolecular noncovalent interactions were detected, π···π interactions in 5, C?–?H···π interactions in 2 and C?–?H···π edge-to-face (T-shaped) arrangements in 3, 4, 6, and 7.     

The synthesis and liquid crystal transition temperatures of some weakly polar nematic methyl (E)-[trans-4-substituted-cyclohexyl]-allyl ethers

Abstract

We have introduced an oxygen atom and a carbon-carbon double bond with a trans-configuration (E) into the terminal alkyl chain of a wide variety of liquid crystalline cyclohexane derivatives to produce a variety of new methyl (E)-allyl ethers. The melting points and tendency to form smectic mesophases are often low, while nearly all of the compounds prepared exhibit a nematic phase. Thus, even two-ring derivatives can exhibit nematic phases over a wide temperature range (≤80°C), sometimes starting below room temperature (T _m≈10°C). Comparisons with the corresponding derivatives incorporating either just an oxygen atom or just a carbon-carbon double bond in the same position indicate that synergetic effects lead to broader nematic phases than would otherwise have been expected. Thus many of the new methyl (E)-allyl ethers exhibit nematic phases over a wider temperature range than the corresponding materials with an unsubstituted alkyl chain attached to the cyclohexyl ring. The new compounds are easily prepared from known starting materials. Many intermediates are themselves liquid crystalline. This allows investigation of the relationship between liquid crystal transition temperatures and the nature of the terminally substituted alkyl chain (for example, incorporating C[dbnd]C, OH, CO₂C₂H₅ and OCH₃ groups).     

New isothiocyanato liquid crystals containing thieno[3,2-b]thiophene central core

New isothiocyanato liquid crystal (LC) materials based on thieno[3,2-b]thiophene core have been synthesised and characterised. Their mesomorphic and physical properties were evaluated. The results indicate that most of the new compounds exhibit only enantiotropic smectic A phases with high clearing points, and the difluorinated compounds (A3 and A6), in particular, also display a stable nematic phase with low melting points. Compared with the corresponding biphenyl and thiophene-phenyl analogues, these thieno[3,2-b]thiophene-based compounds possess increased birefringence (the highest value found to be 0.40) and mesogenic phase intervals. These new thieno[3,2-b]thiophene-based LCs exhibit a high birefringence and a high clearing point and are of potential use as components of high birefringence mixtures.     

Gas chromatographic study of the thermal and analytical properties of a nematic luquid crystal and its cupric complex

The nematic compound N-4-(2′-(4″-dodecyloxybenzoyloxy)-4′-do-decyloxy)azobenzenyl-4-dodecyloxysalicylideneimine, known as LH, and its cupric complex, bis[N-4-(2′-(4″-dodecyloxybenzoyloxy)-4′-dodecyloxy)azobenzenyl-4-dodecyloxysalicylidene]iminato of copper (II), known as CuL₂ have been used as stationary phases for gas chromatography. The thermal properties of LH and CuL₂ have been determined with conventional metal columns, using n-alkanes as solute probes. Plots of In V⁰_g against 1/T clearly show the temperature transitions of LH and CuL₂. The analytical capabilities of the two stationary phases were established by use of 25 m glass capillary columns. Satisfactory separations were obtained for positional hydrocarbon and halocarbon isomers, aromatic and polyaromatic compounds, and volatile essential oil constitutents.     

Synthesis of a novel [60]fullerene pearl-necklace polymer,poly(4,4′-carbonylbisphenylene trans-2-[60]fullerenobisacetamide)

A novel [60]fullerene pearl-necklace polymer, poly(4,4′-carbonylbisphenylene trans-2-[60]fullerenobisacetamide), was synthesized by a direct polycondensation of trans-2-[60]fullerenobisacetic acid with 4,4′-diaminobenzophenone in the presence of large excesses of triphenyl phosphite and pyridine. In the present polymer, [60]fullerene pearls and diamine linkers were attached to each other by methano-carbonyl connectors. The molecular weight M_w of the polymer was determined to be 4.5 × 10⁴ on the basis of the TOF-MS, and a GPC analysis of the polymer using polystyrene standards showed a weight-average molecular weight of 5.3 × 10⁴. The UV-vis spectrum of the resultant polymer in N,N-dimethylacetamide (DMAc) exhibited a broad absorption (λ_max 310 nm, ε 2.1 × 10⁴ L · mol⁻¹ · cm⁻¹), tailing to longer wavelengths, and a fluorenscence peak centered at 550 nm was observed in DMAc. There was observed a large downfield-shift of the cyclopropane methyne proton in the ¹H-NMR spectra from 4.57 ppm of the ethyl ester to 5.78 ppm of the polyamide. These observations indicate that the present polyamide is a high-molecular-weight [60]fullerene pearl-necklace polymer and that the cyclopropane rings are efficient to make the [60]fullerene cages and the diamine components conjugatable. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3632–3637, 1999     

Previously undescribed benzoxepins with bioactivities against inducible pro-inflammatory cyclooxygenase and lipoxygenase from Rhizophora annamalayana Kathir

Two unprecedented benzoxepins were obtained from the ethyl acetate fraction of the leaves of Rhizophora annamalayana Kathir, and characterized as 4-(11-(hydroxymethyl)-10-methylpentan-2-yl)-4, 5-dihydrobenzo[c]oxepin-1(3H)-one (1) and (E)-methyl-14-hydroxy-4-(11-(5-hydroxy-1-oxo-3,4,5-tetrahydrobenzo[c]oxepin-4-yl)ethyl)-10-methylhept-11-enoate (2). The benzoxepin 2 exhibited greater 1, 1-diphenyl-2-picrylhydrazyl and 2, 2′-azino-bis-3 ethylbenzothiozoline-6-sulfonic acid diammonium radical scavenging assays (IC₅₀ 0.68 and 0.84 mg/mL, respectively) than those recorded with 1 (IC₅₀ 0.70 and 0.89 mg/mL, respectively). The tetrahydrobenzo[c]oxepin analogue (2) exhibited significantly great cyclooxygenase-2 and 5-lipoxygenase inhibitory properties (IC₅₀ 0.87 and 0.94 mg/mL, respectively), while compared with its dihydrobenzo[c]oxepin-1(3H)-one isoform (1) (IC₅₀ 1.16 and 1.64 mg/mL, respectively). The dihydrobenzo[c]oxepin-1(3H)-one isoform (2) exhibited significantly greater selectivity index (~2) than synthetic ibuprofen (0.44) (p < 0.05), which attributed the higher anti-inflammatory selectivity of the former against inducible pro-inflammatory cyclooxygenase-2 than its constitutive isoform (cyclooxygenase-1). No significant difference in 5-lipoxygenase (5-LOX) inhibitory activities were apparent between compound 2 (IC₅₀ 0.94 mg/mL) and synthetic ibuprofen (IC₅₀ 0.93 mg/mL).     

Cd(II) and Cu(II) coordination polymers based on a multidentate N-donor ligand: syntheses,crystal structures,optical band gaps,and photoluminescence

Four Cd(II)- and Cu(II)-containing coordination polymers (CPs) based on a multidentate N-donor ligand and varied dicarboxylate anions, [Cd(3,3′-tmbpt)(p-bdc)]·2.5H₂O (1), [Cd(3,3′-tmbpt)(m-bdc)]·2H₂O (2), [Cu(3,3′-tmbpt)(m-bdc)]·H₂O (3), and [Cu(3,3′-tmbpt)(p-bdc)]·2H₂O (4), where 3,3′-tmbpt = 1 ? ((1H-1,2,4-triazol-1-yl)methyl)-3,5-bis(3-pyridyl)-1,2,4-triazole, p-H₂bdc = 1,4-benzenedicarboxylic acid, and m-H₂bdc = 1,3-benzenedicarboxylic acid, have been prepared hydrothermally. The structures of the compounds were determined by single-crystal X-ray diffraction analyses and further characterized by infrared spectra and elemental analyses. Compound 1 exhibits a 3-D twofold interpenetrating framework with a 6⁵·8 CdSO₄ topology. Compound 2 is a 2-D layer containing meso-helical chains with a 4⁴·6² sql topology. Compound 3 shows a 1-D → 3-D interdigitated architecture while 4 displays a 2-D → 3-D interdigitated architecture. The structural differences of the compounds indicate that the dicarboxylate anions and the central metal ions play important roles in the resulting structures of CPs. Optical band gaps and solid-state photoluminescent properties have also been studied.     

Synthesis,characterization, crystal structure,and DNA binding of two copper(II)–hydrazone complexes

Two new Cu(II)–hydrazone complexes, [Cu(L)(Hbpe)ClO₄]·ClO₄·[Cu(L)Cl] (1) and [Cu(HL)₂]·1.5ClO₄·0.5OH (2) (where HL?=?(E)-N′-(1-(pyridine-2-yl)ethylidene)benzohydrazide and bpe = trans-1-(2-pyridyl)-2-(4-pyridyl)ethylene), have been synthesized and characterized by physicochemical methods. The structures of the complexes have been established by single-crystal X-ray diffraction direct methods, which reveal that the metal ions have distorted square-pyramidal and square-planar geometries in 1, and a distorted octahedral geometry in 2. DNA binding of HL, 1, and 2, performed by UV–vis titration in tris-buffer medium, yielded binding constants, which are 9.5 × 10³, 1.88 × 10⁴, and 4.66 × 10⁴ M^?1, respectively. Viscosity measurements suggest a surface or groove-binding mode of interaction between CT-DNA with HL, 1, and 2.