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.     

Complexes of N′-(4-phenyl thiazole-2-yl) thiourea with some first row transition metals

Metal complexes of N′-(4-phenyl thiazole-2-yl) thiourea (L) possessing the stoichiometry, [MLX₂] (M = Cu²⁺; X = Cl⁻, Br⁻, NO₃⁻ and ClO₄⁻), (M = Ni²⁺; X = Cl⁻), (M = Co²⁺; X = Cl⁻, NO₃⁻) have been isolated and studied. Tentative geometry of the complexes has been deduced by elemental analyses, magnetic and spectroscopic techniques. Fungicidal screening of the complexes has been made against Helminthosporium oryzae, Fusarium oxysporium and Aspergillus niger.     

Synthesis and characterization of homologous series with chiral (S)‐1‐methylpropyl terminal substituent

Homologous series of liquid crystalline azoesters and azomethine esters consisting of a (S)‐1‐methylpropyl group attached in one of the terminal positions have been synthesized and thermally characterized. All twenty‐four derivatives from both series, namely, the 4‐(4‐n‐alkoxybenzoyloxy)‐4′‐1‐(S)‐methylpropylazobenzenes and 4‐(4‐n‐alkoxybenzoyloxy)benzylidene‐4′‐1‐(S)‐methylpropylanilines exhibit mesomorphism. The lower members of the homologous series show a chiral nematic phase while the higher members show smectic C*, smectic A as well as chiral nematic mesophases. The homologues have been characterized using IR, NMR and UV‐Visible, spectroscopies, X‐ray diffraction and DSC. Their mesomorphic properties are compared with those of structurally related homologous series.     

Synthesis and characterization of complexes of the first transition series cations with 2,2′-biimidazole and 2,2′-biimidazolate

Mononuclear [M(hfacac)₂(H₂biim)] complexes, where M = Mn^II, Fe^II, Co^II, Ni^II, Cu^II or Zn^II, hfacac = hexafluoroacetylacetonate, H₂biim = 2,2-biimidazole; dinuclear K₂[M₂(acac)₄(-biim)] (M = Cu^II or Zn^II) and tetranuclear K₂[M₄(acac)₈( ₄-biim)] (M = Co^II or Ni^II) complexes have been prepared and characterized by chemical analysis, conductance measurements, i.r., electronic and e.p.r. spectroscopies and by magnetic susceptibility measurements (in the 2–300 K range). Mn^II, Fe^II and Co^II are in a high spin state. The e.p.r. spectra of Cu^II and Mn^II compounds have been recorded.     

X-ray diffraction,optical birefringence,dielectric and phase transition properties of the long homologous series of nematogens 4-(trans -4′- n -alkylcyclohexyl) isothiocyanatobenzenes

The temperature dependence of density, refractive indices, apparent molecular length and intermolecular distance of 11CHBT, are reported, together with the static dielectric permittivities, ε∥, ε┴, ε _iso of 11CHBT and 12CHBT; the effect of chain length on various physical properties of the CHBT series is also discussed. All the temperatures T _m, T _NI and T _NCr show an odd-even (OE) effect, but transition enthalpies ΔH _m and ΔH _c show no such behaviour. T _m, T _NI and T _NCr and ΔH _m are found to increase with chain length, while ΔH _c shows a maxima at n = 6. At the common reduced temperature T* = 0.98 T_NI, the density of the compounds are found to decrease with increasing chain length while the polarizability parameters α_e, α_o and α increase. However, the volume expansion coefficient, polarizability anisotropy and normalized polarizability anisotropy show a distinct OE effect. Similarly, n _e decreases smoothly with chain length but n _o and Δn show an OE effect like ε┴ and Δε. The ratio ln ?P ₂? /ln ? P ₄? remains closer to Faber theory than MS theory. Effective dipole moments are found to be approximately constant in the series; antiparallel association is observed in all the members. Kirkwood correlation factors g┴ and Δg are found to exhibit an OE effect like ε∥ and ε∥, but g∥ and ε∥ show no such effect. The effects of substitution in the core and end polar group on these properties are also discussed.     

Fractal-like scaling in liquid crystals. Odd–even effect of scaling exponents in the 4,4′-di-n-alkyloxyazoxybenzene homologous series

Abstract

A power law behaviour of dielectric loss versus frequency has been found in members of the 4,4′-di-n-alkyloxyazoxybenzene series. For each member the scaling of the data with respect to v/v _max is possible in the liquid-crystalline temperature range; this suggests a fractal-like geometry in nematic and smectic phases. The values of the scaling exponents, indicating a cooperativity of molecular reorientation around the short axes, exhibit an odd–even effect.     

Sorption and selective properties of binary liquid-crystalline sorbent based on 4-Methoxy-4′-ethoxyazoxybenzene and a cetylated β-Cyclodextrin

The mesomorphous, sorption, and selective properties of a binary sorbent based on achiral liquid crystal 4-methoxy-4′-ethoxyazoxybenzene and macrocyclic heptakis(2,3,6-tri-O-acetyl)-β-cyclodextrin (10.25 wt %) are investigated. Macrocyclic additive was found to induce the formation of a helically twisted nematic phase (N*). The standard and excess thermodynamic functions of sorption by binary sorbent from gaseous phase are determined for 29 organic compounds (n-alkanes, cycloalkanes, arenes, monoatomic alcohols, heterocycles, optical isomers of camphene, limonene, and butanediol-2,3). The investigated sorbent is found to have high structural selectivity over the wide temperature range of the N* mesophase (α _p/m = 1.11–1.06, 95–120°C) and moderately expressed enantioselectivity within the narrow region of transition from the solid crystalline state to the N* mesophase (α_+/? = 1.024–1.088, 91–100°C).     

Thermal and odd–even behaviour in a homologous series of lithium n-alkanoates

Thermotropic phase transition temperatures, enthalpies and entropies of phase changes and odd–even alternation, in a homologous series of anhydrous lithium n-alkanoates, LiC_nH_2n?1O₂ (LiC_8–19 inclusive), have been investigated by differential scanning calorimetry (d.s.c.), hot stage polarizing microscopy and solid state ¹³C NMR spectroscopy. The number of phases observed, between the room temperature microcrystalline solid and isotropic melt, shows a clear dependence on chain length. For LiC_8–13, only one intermediate lamellar II crystalline phase is observed. For LiC_14–19, a lamellar II and high temperature phase are evident. The high temperature phase is characterized by pre-melting and disordering of hydrocarbon chains as they change from nearly all-trans to one with increased gauche conformers. It is probably a solid rotator phase. Odd–even alternation in melting temperature, density and some thermodynamic data result from the relative distance between methyl groups, from opposite layers in a bi-layer. Molecular models indicate that the methyl groups in odd chains are more favourably orientated which lead to a more energetically favoured staggered conformer. As a consequence, the methyl groups, for odd chains, are in closer proximity than even chains. This subtle change in the molecular lattice could account for the presence of polymorphic structures on cooling from the melt.     

Simulations of some physical parameters of homologous series of nBT and nCHBT at 0.3–20.0 THz

ABSTRACT

In this work, the terahertz (THz) absorption of homologous series of isothiocyanobiphenyls (nBT) and 4-(trans-4?-n-alkylcyclohexyl)isothiocyanato-benzene (nCHBT) are simulated by using the density functional theory (DFT) method. Numerical results show that absorption of the tested nematic liquid crystals (NLCs) varies up to 0.04 in the broad range of 0.3–20.0 THz and takes maximum value in the range of 9–14 THz.

In addition, the values of molecular polarisabilities (α_o, α_e) increase with the increase in the number of carbon atoms in the alkyl chain, while refractive indices (n_o, n_e) decreases. The calculated birefringence (Δn) values for nCHBT are approximately twice as large as the birefringence value for nBT. It is crucial to examine these series of nematic liquid crystals at THz frequencies due to the role of soft matter in various switchable THz components.     

Synthesis and Crystal Structure of(p-{2-[p-(5′-Phenyl-1′,3′,4′-oxadiazole-2′-yl)-phenyl]-vinyl}-phenyl)-di-p-tolyl-amine

The crystal of the title compound (C36H29N3O,Mr = 519.62) has been prepared and structurally determined by X-ray single-crystal diffraction. It crystallizes in triclinic P ī space group with the crystal cell parameters: a = 12.544(4), b = 14.112(4), c = 17.770(5)A, α = 96.150(6), β = 106.112(5), γ = 107.156(5)°, V = 2825.7(14) ?3, Z = 4, Dc = 1.221g/cm3, μ(MoKα) = 0.074 mm-1 , F(000) = 1096,the final R = 0.0747 and wR = 0.1632 for 4713 observed reflections with I >2σ(I). The E-stereochemistry of the title compound can be confirmed by the result of the X-ray diffraction analysis.     

Features of the aminomethylation of 7-hydroxy-4′-fluoroisoflavones with primary amines

The behavior of 7-hydroxy-4′-fluoroisoflavones under the conditions of the Mannich reaction with primary amines was studied. New 9-alkyl-substituted 3-(4-fluorophenyl)-9,10-dihydro-4H,8H-chromeno-[8,7-e][1,3]oxazin-4-ones were synthesized. A method was developed for the synthesis of 8-amino- methyl derivatives of isoflavones.     

Heteroleptic ruthenium(II) polypyridine complexes with a series of substituted 2,2′-bipyridine ligands

Five substituted-2,2′-bipyridine ligands L, (4-(p-methylphenyl)-6-phenyl-2,2′-bipyridine (L1), 4-(p-bromophenyl)-6-(p-bromophenyl)-2,2′-bipyridine (L2), 4-(p-bromophenyl)-6-phenyl-2,2′-bipyridine (L3), 4-phenyl-6-(p-bromophenyl)-2,2′-bipyridine (L4), and 4-(p-fluorophenyl)-6-(p-fluorophenyl)-2,2′-bipyridine (L5) were synthesized by stepwise formation. Reaction of cis-[RuCl₂(bpy)₂]?2H₂O or cis-[RuCl₂(phen)₂]?2H₂O and the substituted-2,2′-bipyridine ligands in the presence of KPF₆ afforded the corresponding cationic polypyridine-ruthenium complexes of the type [(bpy)₂Ru(L)](PF₆)₂ (bpy = 2,2′-bipyridine, 1–5) or [(phen)₂Ru(L)](PF₆)₂ (phen = 1,10-phenanthroline, 6–10), respectively. All complexes have been spectroscopically characterized by UV–vis, luminescence, and electrogenerated chemiluminescence. The structures of 1?CH₃COCH₃, 3?CH₃COCH₃, 5?2CH₃COCH₃, 6, 8, 9, and 10 have been determined by single-crystal X-ray diffraction.     

Chromatographic properties of a capillary column with the Aerosil modified with nematic 4-methoxy-4′-ethoxyazoxybenzene

The chromatographic properties of a SCOT capillary column with the Aerosil modified with a nematic liquid crystal of 4-methoxy-4′-ethoxyazoxybenzene were studied. The Rohrschneider constants and retention factors were determined for substances from various classes. The microheterogeneous adsorbent SCOT(SiO₂ + MEAB) belongs to medium-polarity stationary phases by its selectivity. It was shown that, in the temperature range 95–110°C, the studied column possessed high values of para-meta selectivity, efficiency, and capacity with respect to arenes and polar substances. Examples of rapid separations of mixtures containing isomers of different types are presented.     

Investigations of 2,3′-biquinolyl. 9. Reaction of 1′,4′-dihydro-2,3′-biquinolyl with organolithium compounds

The 1,4-dihydro-2,3-biquinolyl reacts with organolithium compounds to form the mixture of 4-R-1,4-dihydro-2,3-biquinolyls and 2-R-1,2-dihydro-2,3-biquinolyls in the ratio analogous to the conversion in the series of 2,3-biquinolyl. The utilization of the complex, the organolithium compound-TMEDA, in this process leads, after treatment of the reaction mixture with water, exclusively to 2-R-1,2-dihydro-2,3-biquinolyls. Treatment with methyl iodide leads to 1-methyl-2-R-1,2-dihydro-2,3-biquinolyls.     

SrIrIn6 – An Intergrowth of SrIrIn4 with Indium Slabs

The indium-rich intermetallic compound SrIrIn₆ was synthesized from the elements in a sealed tantalum ampoule at 1173 K, followed by slow cooling for crystal growth. SrIrIn₆ crystallizes with a new structure type which was characterized by X-ray powder and single crystal diffraction: Pmma, a = 852.34(2), b = 434.54(5), c = 1059.18(6) pm, wR₂ = 0.0178, 884 F² values, and 32 variables. The SrIrIn₆ structure shows two basic building units: (i) Ir@In₉ tricapped trigonal prisms (261–292 pm Ir–In) and (ii) distorted bcc In@In₈ cubes (301 to 329 pm In–In). The strontium cations fill cages within the complex three-dimensional [IrIn₆] network and have coordination number 13 (Sr@In₁₃) in form of a tricapped pentagonal prism. The SrIrIn₆ structure can be described as a simple intergrowth variant of SrIrIn₄ (LaCoAl₄ type) with indium slabs. The crystal chemical similarities with the structures of SrIrIn₄, SrIr₂In₈ and Eu₃Ir₂In₁₅ are discussed.     

Complexes of lanthanide perchlorates with 4-N-(2′-hydroxy-1′-naphthylidene)aminoantipyrine

Lanthanide perchlorate complexes with 4-N-(2′-hydroxy-1′-naphthylidene) aminoantipyrine [HNAAP(HL)] of types [Ln(L)₂ClO₄] (where Ln = La, Pr, Nd or Sm) and [Ln(HL)₄](ClO₄)₃ (where Ln = Gd, Tb, Dy, Ho or Y) have been synthesized and characterized. HNAAP acts as a monovalent terdentate ligand in the complexes of the lighter lanthanides and as a neutral bidentate ligand in the complexes of the heavier lanthanides. The perchlorate group is coordinated only in the complexes of the lighter lanthanides.     

Complexes of Some Metal Nitrates with 4′-Nitrobenzo-15-Crown-5

Complexes of Ag, Cu, Ca, Nd, and Er nitrates with 4-nitrobenzo-15-crown-5 (NB15C5) were synthesized and their IR absorption spectra were studied. Macrocyclic conformation in the complexes was determined. The structures of the complexes were proposed with account of the data of IR absorption spectra and of the previous X-ray diffraction study. In the Ag, Cu, and Ca complexes, NB15C5 was found in the inner sphere, while in the Nd and Er complexes, it was found to be the outer-sphere ligand.     

A phase polymorphism N?SAd?I in liquid-crystalline polymethacrylates with 4′-trifluoromethoxyazobenzene mesogenic side groups

The mesophase behaviour of liquid-crystalline polymethacrylates with 4′-trifluoromethoxyazobenzene mesogens and alkylene spacers $ \left( {\rlap{--} ({\rm CH}_{\rm 2} \rlap{--} )_n ,n = 2 - 6} \right) $ in the side chains was investigated and compared with that of the corresponding non-fluorinated polymers. The fluorinated polymers with spacer lengths n = 5 and 6 are the first side-group liquid-crystalline polymethacrylates showing a nematic phase below a smectic A phase.