Non‐symmetric liquid crystal trimers

Four homologous series of non‐symmetric linear liquid crystalline trimers, the 4‐[(4‐{n‐[4‐(4‐methoxy‐phenylazo)phenoxy]alkyloxy}benzylidene)amino]benzoic acid 6‐[4‐(4‐methoxyphenylazo)phenoxy]hexyl esters, 4‐[(4‐{n‐[4‐(4‐cyanophenylazo)phenoxy]alkyloxy}benzylidene)amino]benzoic acid 6‐[4‐(4‐methoxyphenylazo)phenoxy]hexyl esters, 4‐[(4‐{n‐[4‐(4‐methoxyphenylazo)phenoxy]alkyloxy}benzylidene)amino]benzoic acid 6‐[4‐(4‐cyanophenylazo)phenoxy]hexyl esters and 4‐[(4‐{n‐[4‐(4‐cyanophenylazo)phenoxy]butoxy}benzylidene)amino]benzoic acid 6‐[4‐(4‐cyanophenylazo)phenoxy]hexyl esters, have been synthesized and characterized. In each series one spacer was held constant while the length of the second was varied from 3 to 12 methylene units. All these trimers were nematogenic and exhibited pronounced odd–even effects in both their clearing temperatures and associated entropies. Only two of the trimers exhibited a smectic phase, and specifically those containing two differing terminal mesogenic groups and an undecyl spacer. This strongly suggests the driving force for smectic phase formation is a combination of molecular shape and a specific interaction between unlike mesogenic units. The smectic phase has been assigned as a triply‐intercalated alternating smectic C phase, the first example of its kind.     

The role of a liquid crystal oligomer in stabilizing blue phases

A novel liquid crystal oligomer, 4‐(4‐cyanophenyl)phenyl 4‐octyloxy‐2‐{7‐{4‐[4‐(4‐hexylphenyl)‐2,3‐difluorophenyl]phenyloxy}heptanoyloxy}benzoate, was prepared and found to exhibit a wide temperature range of a nematic phase in spite of being far from a rod‐like structure. Furthermore, the compound induced blue phases in the mixture with a chiral smectic liquid crystal. The molecular shape and its 2,3‐difluorophenyl unit play a role in stabilizing the blue phases.     

Liquid crystalline behaviour of benzoic acid derivatives containing alkoxyazobenzene

Liquid crystal trimers based on the hydrogen bonding dimerization of 4‐{n‐[4‐(4‐m‐alkoxy‐phenylazo)phenoxy]alkoxy}benzoic acid (BAm‐n) have been synthesized and characterized. Temperature‐dependent FTIR spectroscopic studies showed that the carboxylic acid groups in BAm‐n are associated to form H‐bonded cyclic dimers both in their crystalline and liquid crystalline phases. The trimers exhibited enantiotropic liquid crystalline behaviour except for BA1‐3 which showed monotropic behaviour, and the mesophases changed from nematic to smectic phase, with the increase of length of the spacer and the terminal substituents. Pronounced odd–even effects in the melting temperatures, clearing temperatures and nematic–isotropic enthalpy changes were observed.     

New metallomesogenic polymers built by self-assembly of non-mesomorphic stilbazole dimers and CF3SO3Ag through coordination bonds

Supramolecular liquid-crystalline main-chain polymers have been obtained by self-assembly of non-mesomorphic bifunctional ligands and a transition metal ion. Stibazole dimers, bis[2-(2-{4-[2-(4-pyridyl)vinyl]phenoxy}ethoxy)ethyl] ether (1) and 1,2-bis[2-(2-{4-[2-(4-pyridyl)vinyl]phenoxy}ethoxy)ethoxy]benzene (2) have been synthesized and complexed with silver trifluoromethanesulfonate (CF₃SO₃Ag). The metallomesogenic polymeric complexes formed by coordination bonds between the pyridyl groups of the stilbazole dimers and the silver ion exhibit smectic phases.     

Structures of Two Spiropyrans in the Open and Closed Form

The crystal structure of the photochromism compound 3-{3,3-dimethyl-6'-nitrospiro[2'H-chromene-2,2'-(2,3-dihydro-1H-indole)]-1-yl}-propanoic acid, SP1, has been characterized by X-ray crystallography. We compared it with the crystal structure of 3-{2-[2-(3,5-dinitro-2-oxidophenyl)ethyl]-3,3-dimethyl-3H-indol-1-ium-1-yl}-propanoic acid. SP2 solvated with two DMF molecules that was obtained earlier. We found that great differences existed between them. Such differences can also be easily found by their [¹H]NMR and IR spectra. Their photochromic behaviors in solutions were investigated by UV-vis absorption with the aid of ultraviolet irradiation, leading to the conclusion that SP1 tended to the closed form while SP2 tended to be the open form both in solution and in the solid state.     

Synthesis and characterization of liquid crystalline polyacrylates and non-liquid crystalline polypyrroles from bifunctional monomers

Two kinds of polymerizations of liquid-crystalline N-{{W-{4-[4-(11-acryloyloxy)undecanoxybenzoyl]biphenyleneoxy}alkyl}}pyrrole gave a side-chain liquid-crystalline polyacrylate containing pyrrole group and a non-liquid crystalline polypyrrole containing acrylate group. Liquid crystallinity was determined by DSC and optical polarizing microscope measurements. The monomers having hexyl or decyl group as the alkyl group exhibited an undefined smectic, smectic B, and smectic A phases on the heating stage. The radically polymerized polyacrylate derivatives containing the pyrrole group showed smectic A, smectic C, and undefined smectic phases on the cooling stage. On the other hand, soluble N-substituted polypyrrole derivatives containing the terminal acrylate group which were prepared by chemical oxidative polymerization by ferric chloride catalyst did not show liquid crystallinity. Structure analysis of the polypyrroles performed by ¹H and ¹³C-NMR and FT-IR spectroscopies demonstrated that the polymerization occurred at the pyrrole ring. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3877–3887, 1999     

Crystal–nematic phase separation in an asymmetric liquid crystal dimer possessing a terminal hydroxyl group

We prepared an asymmetric liquid crystal dimer possessing a terminal hydroxyl group, 2-{4-{7-[4-(4-cyanophenyl)phenyloxy]heptyloxy}phenyl}-5-(6-hydroxyhexyloxy)pyrimidine, and investigated the phase transition behaviour using polarising optical microscopy and differential scanning calorimetry. The compound exhibited an enantiotropic nematic phase. On cooling, two distinct domains were formed during the nematic-to-crystal phase transition. During heating, one domain melted at 126.4°C to the N phase, whereas the other domain changed to the N phase at 144.6°C. Therefore, the crystal and nematic phases coexisted at a temperature of 18.2 K. The coexistence behaviour characteristics depend on the cooling rate. We discuss the manner in which intermolecular interactions affect the phase transition behaviour.     

Reactions with Hydrazonoyl Halides 611: Synthesis of 2,3-Dihydro-1,3,4-Thiadiazoles

2-[1,2-Diaza-3-(2,3-dimethyl-5-oxo-1-phenyl(3-pyrazolin-4-yl))prop-2-enylidene]-3-phenyl-5-substituted 1,3,4-thiadiazolines and 2-{[4-(2,3-dimethyl-5-oxo-1-phenyl(3-pyrazolin-4-yl))(1,3-thiazol-2-yl)]cyanomethylene}-3-phenyl-5-substitu- ted 1,3,4-thiadiazolines were synthesized from hydrazonoyl halides and 4-{-2-aza-2-[(methylthiothioxomethyl)amino]vinyl}-2,3-dimethyl-1-phenyl-3-pyrazoin-5-one and 2-[4-(2,3-dimethyl-5-oxo-1-phenyl-3-pyrazolin-4-yl)-1,3-thiazol-2-yl]ethane-nitrile, respectively. All synthesize compounds were elucidated by elemental analysis, spectra, and alternative synthesis routes, whenever possible.     

A NOVEL SYNTHESIS OF 2-SUBSTITUTED-4H-THIENO [2,3-d][1,3] OXAZIN-4-ONE AND 2,3-DISUBSTITUTED THIENO [2,3-d]PYRIMIDIN-4(3H)-ONE DERIVATIVES

Abstract

The synthesis of acetic 2-{[1-methyl-2-(4-oxo-5,6,7,8-tetrahydro-4H-benzo [4,5]-thieno [2,3-d] [1,3-oxazin-2-yl)ethylidene]amino}-4,5,6,7-tetrahydrohenzo[b]thiophene ?3-carboxylic acid anhydride 5 and 2-(oxopropyl)-5,6,7,8-tetrahydro-4H-benzo-[4,5] thieno[2,3-d][1,3]oxazin-4-one 7, has been achieved in three steps from ethyl 2-amino-4,5,6,7-tetrahydrobenzo(b]thiophene-3-carboxlate 1 via the reaction with ethyl acetoacetate followed by hydrolysis and acetic anhydride-induced cyclization. The 2-substituent in compound 5 has two functional groups i.e. active methylene and acid anhydride which are suitably located for intramolecular transformation. Thermal and/or base catalyzed intramolecular cyclization of 5 afforded 2-(4-acetoxy-(hydroxyl)-2-methyl-5,6,7,8-tetrahydrobenzo[4,5] thieno[2,3-b]pyridin-3-yl)-5,6,7,8- tetrahydro-4H-benzo[4,5]thieno[2,3-d] [1,3]oxazin-4-one 10 and 9 respectively. Treatment of 5 with hydrazine hydrate, aromatic and/or heterocyclic amines induced the same intramolecular cyclization with a concomitant oxazine-pyrimidine interconversion to give 3-amino(aryl or heteryl)-2-(4-hydroxy-5,6,7,8-tetrdhydrobenzo-[4,5]thieno[2,3-b]pyridin-3-yl)-3,4,5,6,7,8-hexahydrobenzo[4,5] thieno[2,3-d] pyrimid in-4-one 11–14 respectively.     

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.     

Synthesis of Some New Thiazoles and Pyrazolo[1,5-a]pyrimidines Containing an Antipyrine Moiety

Ethyl 2-{2-[4-(2,3-dimethyl-5-oxo-1-phenyl-3-(pyrazolin-4-yl)]-2-cyano-1-(phenylamino)vinylthio}-acetate, 2-[4-(2,3-dimethyl-5-oxo-1-phenyl-(3-pyrazolin-4-yl))(1,3-thiazol-2-yl)]2-(4-oxo-3-phenyl-(1,3-thiazoilidin-2-ylidene))ethanenitrile, 2-[4-(2,3-dimethyl-5-oxo-1-phenyl(3-pyrazolin-4-yl))(1,3-thiazol-2-yl)]-2-(4-methyl-3-phenyl(1,3-thiazolin-2-ylidene))ethanenitrile, 2-(5-acetyl-4-methyl-3-phenyl(1,3-thiazolin-2-ylidene))-2-[4-(2,3-dimethyl-5-oxo-1-phenyl(3-pyrazolin-4-yl))(1,3-thiazol-2-yl)]ethanenitrile, and ethyl 2-(cyano(4-(2,3-dihydro-1,5-dimethyl-3-oxo-2-phenyl-1H-pyrazol-4-yl)thiazol-2-yl)methylene)-2,3-dihydro-4-methyl-3-phenylthiazole-5-carboxylate were synthesized by treatment of 2-(4-(2,3-dihydro-1,5-dimethyl-3-oxo-2-phenyl-1H-pyrazol-4-yl)thiazol-2-yl)-3-mercapto-3-(phenylamino)-acrylonitrile with appropriate halo ketones or halo esters. Also, 4-{2-[5,7-dimethyl-2-(phenylamino)(7a-hydropyrazolo[1,5-a]pyrimidin-3-yl](1,-thiazol-4-yl)}-2,3-dimethyl-1-phenyl-3-pyrazolin-5-one derivatives were synthesized via reaction of 4-{2-[5-amino-3-(phenylamino)pyrazolin-4-yl](1,3-thiazol-2-yl)}-2,3-dimethyl-1-phenyl-3-pyrazolin-5-one with β-diketone or β-keto ester. All synthesized compound were established by elemental analysis, spectral data, and alternative synthesis whenever possible.     

Reaction of 4-Aryl-1-(4-oxo-3,4-dihydrothieno-[2,3-d]pyrimidin-2-yl)thiosemicarbazides with Dimethyl Acetylenedicarboxylate

4-Aryl-1-(4-oxo-3,4-dihydrothieno[2,3-d]pyrimidin-2-yl)thiosemicarbazides react with dimethyl acetylenedicarboxylate in methanol to give the corresponding methyl {3-aryl-4-oxo-2-[(4-oxo-3,4-dihydro-thieno[2,3-d]pyrimidin-2-yl)hydrazono]-1,3-thiazolidin-5-ylidene}acetates, whereas in dioxane methyl 5-aryl-amino-2-methoxycarbonylmethyl-3-(4-oxo-3,4-dihydrothieno[2,3-d]pyrimidin-2-yl)-2,3-dihydro-1,3,4-thiadiazole-2-carboxylates are mainly formed.     

Synthesis,Crystal Structure,and DFT Study of a New Derivative of Pyrido[2,3-d]pyrimidine

Russian Journal of General Chemistry - N-{4-[(6-bromopyrido[2,3-d]pyrimidin-4-yl)oxy]phenyl}morpholine-4-carboxamide has been synthesized as a derivative of pyrido[2,3-d]pyrimidine that...     

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.     

An α-Diimine-Nickel(II) catalyst bearing an electron-withdrawing substituent for olefin polymerization

A Br-substituted α-diimine ligand, bis[N,N′-(4-bromo-2,6-dimethylphenyl)imino]-2,3-butadiene L1, and its corresponding Ni(II) complex, {bis[N,N′-(4-bromo-2,6-dimethylphenyl)imino]-2,3-butadiene} dibromonicke [NiBr ₂ (L1)], have been synthesized and characterized. The crystal structure of the free ligand (L1) was determined by X-ray crystallography. Two α-diimine-Ni(II) catalysts, {bis[N,N′-(2,4,6-dimethylphenyl)imino]-2,3-butanedione} dibromonickel [NiBr ₂ (L2)] and {bis[N,N′-(2,6-dimethylphenyl)imino]-2,3-butanedione} dibromonickel [NiBr ₂ (L3)], were also synthesized and characterized for comparison. The complex [NiBr ₂ (L1)], when activated by diethylaluminum chloride, produces the most active catalytic system for the polymerization of ethylene among the three complexes. NMR analysis shows that the degree of branching of polyethylene increases in the presence of electron-withdrawing groups under the same reaction conditions.     

Synthesis of N-arylsulfonyl-2-aryl(hetaryl)aminoacetic acids

Hydrolytic transformations of 4-[2,2,2-trichloro-1-(arylsulfonylamino)-and-(ethoxycarbonylamino)ethyl]phenyloxy(or sulfanyl)acetic acids under microwave irradiation in alkaline medium involve both trichloromethyl group and ester fragment to give N-arylsulfonyl-2-[4-carboxymethyloxy(or sulfanyl)phenyl]-2-aminoacetic acids in good yields. Hydrolysis of methyl 4-[2,2,2-trichloro-1-(arylsulfonylamino)ethyl]phenyloxy(or sulfanyl)acetates without microwave activation occurs only at the ester group with quantitative formation of 4-[2,2,2-trichloro-1-(arylsulfonylamino)ethyl]phenyloxy(or sulfanyl) acetic acids. N-[2,2,2-Trichloro-1-(1-naphthyl, 2-furyl, and 1-methylindol-3-yl)ethyl]-4-chlorobenzenesulfonamides in alkaline medium under microwave irradiation were converted in 10–15 min into the corresponding N-(4-chlorophenylsulfonyl)-2-aryl-2-aminoacetic acids in preparative yields.     

Competition between micro-segregation and anti-parallel alignment of an amphiphilic rod-like liquid crystal

Recently, we reported that a rod-like molecule, 4-[4-(7-hydroxyheptyloxy)phenyl]-1-(4-hexylphenyl)-2,3-difluorobenzene, exhibited a nematic phase with a layered structure and smectic C phases consisting of three states. We prepared a homologous series of the rod-like molecules in which a 2,3-difluoro-1,4-diphenylbenzene unit and a hydroxyl unit are connected via a flexible methylene spacer. We investigated their physical properties using polarised optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Although they showed nematic, smectic A and smectic C phases, the phase structures were found to depend on the flexible spacer length. Those compounds possessing a shorter spacer length than a heptyl unit exhibited bilayered smectic A and smectic C phases, whereas those possessing a longer spacer length than a heptyl unit showed conventional monolayered smectic A and smectic C phases. A nematic phase with a smectic-like layer ordering was observed for the compound possessing an octyl unit. The structure–property relations of the amphiphilic compounds are discussed.     

Synthesis and some transformations of methyl [4-(oxoacetyl)phenyl]carbamate

The oxidation of methyl (4-acetylphenyl)carbamate with selenium dioxide in dioxane–water (30: 1) gave methyl [4-(oxoacetyl)phenyl]carbamate whose condensation with ethyl acetoacetate or diethyl malonate and hydrazine hydrate afforded ethyl 3-methyl-6-[4-(methoxycarbonylamino)phenyl]pyridazine-4-carboxylate and methyl {4-[5-(hydrazinecarbonyl)-6-oxo-1,6-dihydropyridazin-3-yl]phenyl}carbamate, respectively. The reaction of methyl [4-(oxoacetyl)phenyl]carbamate with o-phenylenediamine in dimethylformamide–ethanol on heating led to the formation of methyl [4-(quinoxalin-2-yl)phenyl]carbamate. Methyl {4-(5,7-dioxo- 4,4a,5,6,7,8-hexahydropyrimido[4,5-c]pyridazin-3-yl)phenyl}carbamate and methyl {4-(5-oxo-7-sulfanylidene- 4,4a,5,6,7,8-hexahydropyrimido[4,5-c]pyridazin-3-yl)phenyl}carbamate were synthesized by reactions of methyl [4-(oxoacetyl)phenyl]carbamate with barbituric and thiobarbituric acids, respectively, and hydrazine hydrate in the presence of zirconyl chloride octahydrate at room temperature.     

Substituent effect of fluorine atom on benzothiadiazole bridging unit in dye sensitized solar cells

Dye sensitized solar cells performances using two organic dyes with fluorinated-benzothiadiazole spacer, 3-{5-[7-(5-{4-[Bis(9,9-dimethyl-9H-fluoren-2-yl)-amino]-5-fluoro-phenyl}thiophen-2-yl)benzo-[1,2,5]thiadiazol-4-yl]thiophen-2-yl}-2-cyano acrylic acid (JK-311) and 3-{5-[7-(5-{4-[Bis(9,9-dimethyl-9H-fluoren-2-yl)-amino]-5,6-difluorophe-nyl}thiophen-2-yl)benzo-[1,2,5]thiadiazol-4-yl]thiophen-2-yl}-2-cyano acrylic acid (JK-312), were systematically investigated by solar simulation equipment, stepped light-induced transient measurements of photocurrent and voltage, and electrochemical impedance spectroscopy. To investigate substituent effect of fluorine atom on benzothiadiazole, molecular orbital calculations of two dyes using a time dependent density functional theory model with B3LYP/3-31G* were also carried out. JK-312 showed a unique electronic transition from HOMO-1 to LUMO. Short circuit current and open-circuit voltage in DSSCs performances were increased by the introduction of fluorine atom into spacer segment, compared to fluorine-free dyes.     

Liquid-crystalline behaviour of some bis(4-alkyloxyphenyl) thiazolo [5,4-d] dithiazoles

The preparation of liquid-crystalline 2,5-bis(4-alkyloxyphenyl) thiazolo [5,4-d] dithiazoles (ATT_n), in which the alkyl group is C_nH_{2n + 1} (where n = 1 to 10, 12), has been described. Mesomorphic properties and phase transitions as determined by polarizing hot stage microscopy and differential scanning calorimetry are discussed as a function of the number of carbon atoms in the alkyloxy chain. The exhibition of tilted smectic phases (smectic C and smectic I) by these compounds is an interesting feature since there is no significant central dipole moment transverse to these molecules.