The effect of a lateral substituent on the mesomorphic properties in a series of ferroelectric liquid crystals with a 2-alkoxypropionate unit

A new series of ferroelectric liquid crystal materials containing a lateral methyl group on the aromatic ring of the alkoxybenzoate unit has been synthesized and investigated. These materials exhibit a wide temperature range of ferroelectric SmC* phase on cooling (including supercooling) with a very high spontaneous polarization. All phase transition temperatures are lower when compared with those of similar non-substituted materials. In comparison with the compounds containing the lateral methoxy group, only the SmC*-Cr transition changed significantly. The values of spontaneous polarization are mostly increased compared with both non-substituted and methoxy substituted compounds.     

Effect of lateral substitution by fluorine and bromine atoms in ferroelectric liquid crystalline materials containing a 2-alkoxypropanoate unit

Two homologous series of ferroelectric liquid crystalline compounds with 2-alkoxypropanoate chiral unit containing biphenyl benzoate core laterally substituted by fluorine and bromine have been synthesized and studied. All compounds possess the ferroelectric smectic C* phase over a broad temperature range. For bromine-substituted compounds values of spontaneous polarization reach high values up to 250 nC cm^-2. The effects of the lateral substitution on the phenyl ring far from the chiral centre by methyl and methoxy groups, fluorine, chlorine and bromine atoms on mesomorphic properties and on values of the spontaneous polarization are discussed.     

Effect of lateral substitution by fluorine and bromine atoms in ferroelectric liquid crystalline materials containing a 2‐alkoxypropanoate unit

Two homologous series of ferroelectric liquid crystalline compounds with 2‐alkoxypropanoate chiral unit containing biphenyl benzoate core laterally substituted by fluorine and bromine have been synthesized and studied. All compounds possess the ferroelectric smectic C* phase over a broad temperature range. For bromine‐substituted compounds values of spontaneous polarization reach high values up to 250 nC cm^?2. The effects of the lateral substitution on the phenyl ring far from the chiral centre by methyl and methoxy groups, fluorine, chlorine and bromine atoms on mesomorphic properties and on values of the spontaneous polarization are discussed.     

Synthesis and mesomorphic properties of liquid crystalline [1]benzothieno[3,2-b][1]benzothiophene derivatives

Two new series of chiral aliphatic and aromatic esters of 7-decyl[1]benzothieno[3,2-b][1]benzothiophene-2-carboxylic acid were synthesized and their mesomorphic behaviour studied. While the chiral aliphatic esters exhibited only the SmA phase, the antiferroelectric SmC_A* phase was found for esters with chiral 4-hydroxybenzoates; for one homologue a ferroelectric SmC* phase was also observed. Introduction of lateral substituents in the 3-position of the 4-hydroxybenzoic acids (methoxy, fluoro, chloro, and bromo) led to a reduction of the polymorphism and only the SmA phase remained.     

New series of ferroelectric liquid crystals with four ester groups

Three series of ferroelectric liquid crystals have been synthesized, having three ester groups in the mesogenic core and one ester group in the chiral chain. The ester groups introduced into the core decrease the temperature of crystallization, which results in a broad temperature range ferroelectric smectic C phase in homologues with a long non-chiral chain. These phases exhibit a high spontaneous polarization and relatively short pitch of the helical structure.     

Effect of lateral methoxy substitution on mesomorphic and structural properties of ferroelectric liquid crystals

A new series of materials with a chiral fragment derived from lactic acid and a methoxy group as lateral substituent in different positions of the molecular core was synthesised and investigated. Derivatives with ester or ether linkages of the non‐chiral chain were also studied. Depending on the molecular structure, cholesteric, twist grain boundary smectic A (TGBA*), chiral smectic A (SmA*) or chiral smectic C (SmC*) phases were detected. In derivatives with the ester linkage and a methoxy group at the nearest and the next nearest phenyl ring to the non‐chiral chain these phases completely disappear. On the other hand, a methoxy group on the phenyl ring close to the chiral chain provides a compound with low layer shrinkage at the SmA*–SmC* phase transition (“de Vries” behaviour). The temperature dependence of the spontaneous polarisation, the tilt angle, the layer spacing as well as the complex permittivity were studied and the results discussed in terms of molecular structure.     

New series of chiral ferroelectric liquid crystals with the keto group attached to the molecule core

Two new series of ferroelectric liquid crystals with a keto group attached to the molecular core and a lactate unit as a chiral centre were synthesized and studied. All the compounds exhibit the paraelectric SmA phase and the ferroelectric SmC * phase over very wide temperature ranges and down to room temperature. The main characteristics of the chiral ferroelectric SmC * phase, namely spontaneous polarization, spontaneous tilt angle, and dielectric constant, have been measured to establish their relationship to the length of the terminal chains. The influence of the chiral and non-chiral chain lengths on the helix pitch length is also discussed.     

New series of chiral ferroelectric liquid crystals with the keto group attached to the molecule core

Two new series of ferroelectric liquid crystals with a keto group attached to the molecular core and a lactate unit as a chiral centre were synthesized and studied. All the compounds exhibit the paraelectric SmA phase and the ferroelectric SmC* phase over very wide temperature ranges and down to room temperature. The main characteristics of the chiral ferroelectric SmC* phase, namely spontaneous polarization, spontaneous tilt angle, and dielectric constant, have been measured to establish their relationship to the length of the terminal chains. The influence of the chiral and non-chiral chain lengths on the helix pitch length is also discussed.     

Diazo compounds of the heterocyclic series. 6. Amination of methoxy-substituted 2-naphthyl- and 2-arylazobenzimidazoles

The amination of azo compounds inactivated by quaternization was carried out for the first time using 4-methoxyphenyl-, 2- and 4-methoxynaphthylazobenzimidazoles as examples. In contrast to the quaternary salts of 2-arylazobenzimidazoles, during the amination of the above bases of azo compounds, the substitution of the methoxy group rather than of the hydrogen atom was observed. The anomalous ease of substitution of the methoxy group, located in the naphthalene ring in a position adjacent to the azo bridge was attributed to the manifestation of an ortho-effect, discovered in the series of azo compounds for the first time.For Communication 5, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1209–1214, September, 1991.     

Non-Covalent Interactions in Molecular Systems: Thermodynamic Evaluation of the Hydrogen-Bond Strength in Amino-Ethers and Amino-Alcohols

The intramolecular hydrogen bond (intra-HB) is one of the best-known examples of non-covalent interactions in molecules. Among the different types of intramolecular hydrogen bonding, the NH⋅⋅⋅O hydrogen bond in amino-alcohols and amino-ethers is one of the weakest. In contrast to the strong OH⋅⋅⋅N intramolecular hydrogen bond, the strength of the NH⋅⋅⋅O bond can hardly be measured with conventional spectroscopic methods, even for simple amino-alcohols, since the band belonging to the NH⋅⋅⋅O conformer merges with the free OH band. In this work, we developed a combination of G4 calculations, and a method based on experimental vaporization enthalpies to determine the NH⋅⋅⋅O hydrogen bonding strength. The archetypal compounds for this study are 2-amino-1-ethanol and 3-amino-1-propanol as well as their respective methoxy analogs. Based on these molecules, different series were studied to investigate various factors influencing NH⋅⋅⋅O intra-HB strength. In the first series, the influence of alkylation near the hydroxy or methoxy group and the amino group in sterically hindered aminoalcohols was examined. In the second series, the influence of alkylation of the amino-group was investigated. In the third series, the effect of extending the alkyl chain between functional groups was studied.     

Stepwise and directional synthesis of end-functionalized single-oligomer OPVs and their application in organic solar cells

A new stepwise directional synthetic route to single-oligomer p-phenylenevinylenes (OPVs) has been developed. The first step in the reaction sequence is the condensation of a functionalized benzaldehyde with a novel monomer having a methyl phosphonate ester group in one end and an acetal-protected aldehyde at the other end of a stilbene core. Oligomerization then proceeds stepwise by alternating reaction of the previous aldehyde-terminated OPV fragment with the monomer and deprotection of the acetal. Thus, a series of OPVs with 3, 5, 7, 9, and 11 phenylene vinylene units has been prepared that has an electron-donating methoxy group at one end and an electron-accepting aldehyde group at the other end. Some examples where a dimethylamino group replaced the methoxy group were also prepared. The oligomer with seven phenylene vinylene units was then further derivatized at the aldehyde position to create a series of OPVs with a range of substituents from strongly electron-accepting nitrophenyl to electron-donating methoxyphenyl. Photovoltaic cells were assembled with the synthesized OPVs as the photoactive layer. Illumination under simulated sunlight (AM1.5) gave short circuit currents (Isc) in the range 0.015-0.5 mA cm(-2) and typical open circuit voltages (Voc) of 0.4-0.8 V. The maximum efficiency obtained was approximately 0.1%.     

Delineating noncovalent interactions between the azinomycins and double-stranded DNA: importance of the naphthalene substitution pattern on interstrand cross-linking efficiency

[reaction: see text] Using a series of synthetic azinomycin analogues, it is shown that the efficiency of in vitro DNA interstrand cross-linking is markedly reduced when either the C-5' methyl group or both the C-5' methyl and C-3' methoxy groups are deleted from the naphthalene ring.     

Effect of substituent position and lithium,sodium and potassium on the electronic structure of o-, m- and p-methoxybenzoic acids

We have studied the effect of the substituent position in the ring, and lithium, sodium and potassium ions on the electronic structure of o-, m- and p-methoxybenzoic acids (anisic acids) by the use of FT-IR, FT-Raman, Ar matrix FT-IR and ¹H NMR methods, and ab initio calculations at the B3LYP/6-311++G** level of theory. Characteristic shifts of the bands in the spectra and changes in the band intensities along the metal and ligand series were observed. On the basis of the obtained results we may answer the questions: (1) do the substituents in the benzene ring influence the electronic charge distribution in the carboxylic group of anisic acids and alkali metal anisates, (2) do the metal ions affect the electronic charge distribution in the methoxy group, (3) in what way do the alkali metals affect the electronic system of o-, m- and p-anisic acids? The substitution of lithium, sodium and potassium ions in the carboxylic group of o-, m- and p-anisic acids causes changes in the values of bond lengths and angles, and in the electronic charge distribution in the carboxylic group, methoxy group and aromatic ring. The influence of alkali metals on the electronic structure of the ligands is weaker than the effect of methoxy substituents. The effect of Li, Na and K ions on the aromatic ring of the ligands is mostly noticeable in the case of the ortho isomer. The carboxylic and methoxy groups situated in ortho positions in the ring weaken the effect of the alkali metals on the electronic charge distribution in the carboxylic anion and methoxy group.     

New Cyanoarylporphyrazines with High Sensitivity of Photophysical Parameters to Viscosity as Promising Agents for Photodynamic Therapy

Photophysical properties and photodynamic activity for a series of cyanoarylporphyrazine pigments have been analyzed depending on the nature of the substituents and their position in the aromatic ring. Replacement of the fluorine atom in the para-position with the methoxy group leads to significant increase in the ratio of the dark and photoinduced cytotoxicities, i.e. potential therapeutic index of porphyrazine as photosensitizer in photodynamic cancer therapy.     

Ferroelectric liquid crystals derived from (S)‐2‐(6‐methoxy‐2‐naphthyl)propionic acid with non‐fluorinated or semi‐fluorinated alkanes at a chiral terminal chain

Two series of ferroelectric liquid crystals derived from (S)‐2‐(6‐methoxy‐2‐naphthyl)propionic acid, with non‐fluorinated or semi‐perfluorinated alkanes positioned at a chiral terminal chain, have been synthesized and characterized by differential scanning calorimetry, polarizing optical microscopy and electro‐optical measurements. The non‐fluorinated compounds, 1‐hexyl (S)‐2‐{6‐[4‐(4‐alkanoyloxyphenyl)benzoyloxy]‐2‐napthyl}propionates exhibit rich mesomorphism—the BP_II, N*, TGB_A*, SmA* and SmC* phases. The fluorinated compounds display only the SmA* and SmC* phases, suggesting that the fluorination promotes the formation of smectic phases. In addition, the SmA* and SmC* phases of the fluorinated compounds have enhanced thermal stability as compared with the corresponding phases of the non‐fluorinated compounds. The spontaneous polarization (P _s values) for the non‐fluorinated compounds are higher than those of the fluorinated compounds at any reduced temperature below the SmA*–SmC* transition. The electro‐optical responses measured for these compounds in the ferroelectric phase displayed thresholdless, V‐shaped switching.     

Mechanistic understanding of the unexpected meta selectivity in copper-catalyzed anilide C-H bond arylation

DFT calculations suggest that the unexpected meta product in the copper-catalyzed arylation of anilide is formed via a Heck-like four-membered-ring transition state involving a Cu(III)-Ph species. A competitive electrophilic substitution mechanism delivers the ortho product when a methoxy group is present at the meta position of pivanilide. A series of experiments including kinetic studies support the involvement of a Cu(I) catalyst.     

Possible transition from rod-like to disc-like behaviour in ortho-metallated imine complexes of palladium(II): crystal and molecular structure of three palladium complexes

Two series of ortho-metallated palladium imine complexes are reported that contain a coordinated β-diketonate group. In one group the chain length of the imine is varied while the β-diketone is unchanged; in the other the imine chains are both fixed as methoxy and the structure of the β-diketonate is varied. The mesomorphism of these new complexes is reported and discussed in relation to the search for materials showing a biaxial nematic phase.     

Synthesis and complexation properties towards amino acids of mono-substituted p-sulphonato-calix-[n]-arenes

A series of mono-hydroxy functionalised calix-[n]-arenes, and p-sulphonato-calix-[n]-arenes where n=4, 6 and 8, have been synthesised, with the pendant functions being ethoxycarbonyl methoxy group, 2-carboxy methoxy group, 2-amido methoxy group or 2-amino ethoxy group. With calix-[4]-arene and calix-[6]-arenes the compounds are obtained in good yield by treatment of the relevant p-H-calix-[n]-arene with a suitable metal carbonate, as a weak base, in the presence of one equivalent of the corresponding alkyl bromide. However in the case of calix-[8]-arene, the extremely low solubility of p-H-calix-[8]-arene prevented its use and p-tBu-calix-[8]-arene was used in the monosubstitution reactions. The corresponding sulphonate derivatives were prepared in the case of the 2-carboxy methoxy group, 2-amido methoxy group and 2-amino ethoxy group systems, either by sulphonation of the para-H derivatives or by ipso-sulphonation of the tert-butyl derivatives. The complexation properties of the water-soluble p-sulphonato-derivatives with regard to 11 amino acids have been studied by ¹H NMR titration experiments. The obtained association constants show a 1:1 stoichiometry. The presence of a pendant group at the lower rim of calix strongly modifies the observed association constant as compared to the parent p-sulphonato-calix-[n]-arenes. While generally, the cationic amino acids lysine and arginine bind strongly to all the derivatives, the binding of other amino acids is dependant on the nature of the pendant functions, in particular pendant arm-lateral chain function leads to strong binding with aspartic acid, serine and tryptophan.     

Liquid Crystalline Properties of Side-chain Polymers Bearing the Same Mesogenic Group

The synthesis and properties of a series of new ferroelectric liquid crystal side-chain polymers with the same mesogenic side group but different polymer backbones (polyacrylate, polymethacrylate and polysiloxanes) are described. The polymorphism is studied by optical microscopy, differential scanning calorimetry and X-ray diffraction. All the monomers exhibit at least an S_A and a ferroelectric S*_C phase, as the polymethacrylate and the copolysiloxane. These two polymers and the polyacrylate exhibit also an S*_F phase. © 1997 John Wiley & Sons, Ltd.     

Triorganosilyl Ethers of Benzaldehyde,m-Methoxybenzaldehyde and Anisoles

Synthesis of six new triorganosiloxybenzaldehydes, two m-methoxy-(triorganosiloxy)benzaldehydes, and seven methoxy(triorganosiloxy)benzenes are reported. From comparison of the stability of these compounds in the atmosphere, it is concluded that formyl group shows unfavorable influence and methoxy group shows favorable influence on the stability of these compounds. The oposite influences of these two groups on phenoxysilane linkage seems to connect with the oposite directiones of inductive effect of formyl group and resonance effect of methoxy group on the benzene ring.