Synthesis of novel azoester homologous series of liquid crystalline behavior and the study of mesomorphism dependence on lateral substitution of middle phenyl ring

The titled azoester liquid crystalline homologous series consists of eleven homologues. The pentyl to tetradecyl derivatives of the series are nematogenic without exhibition of smectogenic character. Rest of the members of the series are nonliquid crystalline in nature. Textures of the nematic mesophase are schlieren or threaded type. Transition curves in the phase diagram showed normal phase behavior. Transition temperatures and liquid crystal behavior observed under an optical polarizing microscope equipped with a heating stage. An odd even effect is observed for nematic-isotropic transition curve. Analytical and spectral data confirms the structures of the molecules. Present homologous series is predominant nematogenic and partly nonmesogenic. Average thermal stability for nematic is 125.33°C and nematogenic mesophase length varies between 12°C to 48°C at tetradecyl (C₁₄) and octyl (C₈) derivatives, respectively.     

Synthesis and Evaluation of Liquid Crystal Behavior of a Novel Homologous Series: 4-(4′-n-Alkoxy benzoyloxy) Phenylazo-2″, 6″-dimethylbenzenes

A novel homologous series entitled 4-(4′-n-alkoxy benzoyloxy) phenyl azo 2^″, 6^″-dimethyl benzenes consisting of 12 members is reported. Liquid crystal behavior as a nematogenic mesophase commences from the pentyloxy homologue monotropically and then continues enantiotropically until the last hexadecyloxy homologue without exhibition of any smectogenic behavior. An odd-even effect is observed for nematic-isotropic transition curve of the phase diagram. The textures of the nematic mesophase are of the threaded or Schlieren type. Analytical and spectral data support the molecular structure of the homologues. Transition temperatures of the novel homologues were determined by an optical polarizing microscopy. Liquid crystal properties of a novel homologous series are compared with other known homologous series. The average thermal stability for the nematic phase is 77.1°C.     

Synthesis of novel ester series and study of its mesomorphism dependence on terminal end group with lateral –OCH3 group

Novel liquid crystal (LC) materials of ester derivatives were synthesized and studied with a view to understanding and establishing the effects of molecular structure on LC properties. The novel molecules consist of two phenyl rings bonded through –COO– central group and a laterally substituted methoxy group with –OC_nH_2n+1 as well as –COOCH₃ terminal end groups, and yielded 12 homologous members of an ester series. The C₁ to C₃ members are nonmesomorphic, the C₄ to C₁₂ members are enantiotropic nematic only, and the C₁₄ to C₁₆ members are enantiotropically smectogenic in addition to nematogenic. Transition temperatures and the textures of LC state were observed through an optical polarizing microscope (POM) equipped with a heating stage. The textures of nematic phase are threaded or Schlieren, and that of smectic phase are focal conic of the type A or C. Transition curves of a phase diagram behave in normal manner with the exhibition of an odd-even effect (only N-I). Analytical and spectral data support the molecular structures of the novel ester derivatives. The LC properties of the present series are compared with structurally similar other known series. The average thermal stability of the series is 93°C for smectic and 120.88°C for nematic and the mesogenic phase length ranges between 2°C and 46°C.     

Synthesis and crystal structures of cis- and trans-1-(3′-N, N-dimethylthiocarbamoyl-4′-methoxy)-2-(3″, 4″, 5″trimethoxyphenyl) ethene

The combretastatin A-4 analogue cis-1-(3-N,N-dimethylthiocarbamoyl-4-methoxy)-2-(3,4, 5-trimethoxyphenyl) ethene (1) and its trans stereoisomer (2) were synthesized. The molecular structures of these compounds were obtained by single-crystal X-ray diffraction. Crystallization of 1 occurs in the centrosymmetric monoclinic space group C2/c (No. 15) with a = 21.468(5), b = 7.932(1), c = 23.949(3); and = 100.75(1) and Z = 8. Crystallization of 2 occurs in the centrosymmetric monoclinic space group P2₁/n (No. 14) with a = 11.7825(7), b = 11.562(1), c = 14.911(1) and = 93.294(6); and Z = 4. Details of the synthesis and the structural characterization of the title compounds are presented and discussed.     

Synthesis and structure analysis of 2-(2′-propanonylthio)-3-(o-methyl phenyl) quinazol-4(3H)-one

The three-dimensional molecular and crystal structure of 2-(2'-propanonylthio)3-(o-methyl phenyl)quinazol-4(3H)-one has been determined by X-ray crystallographic methods. This compound crystallizes in the orthorhombic space group P_bca with unit cell parameters: a=9.649(5), b=30.102(10), c=11.403(9)Å. It has been solved by direct methods and refined to a residual index of 0.054. The magnitude of torsion along C16— C11— N3— C4 bond is 93.5(4)°. The dihedral angle between the plane comprising all the ring atoms of quinazoline moiety and the atoms of the methyl substituted phenyl ring is 94.12(1)°. The crystal structure is stabilized by one intramolecular C— HsO interaction and three intermolecular C— HsN contacts.     

Attractive interactions between functional groups in crowded molecules: The solid state structures of diethyl 2-cyano(2′-nitrophenyl)methyltartronate and diethyl (2′-,6′-dinitrophenyl)methyltartronate

The molecular structures of two substituted diethyl tartronates show a variety of interactions between functional groups. Oxygen atoms interact with the electron deficient carbon and nitrogen atoms of nitrile and nitro groups which in response show small distortions from their normal geometries. Short O ··· H contacts between benzyl hydrogen atoms and ortho nitro groups indicate some weak hydrogen bonding effects. Crystal data: C₁₅H₁₆N₂O₇, Mr = 336.3, a = 7.668(2), b = 7.961(3), c = 15.244(3) Å, = 86.78(1), = 81.56(1), = 61.92(1)°, triclinic, P1¯, Z = 2; C₁₄H₁₆N₂O₉, Mr = 356.3, a = 7.786(2), b = 10.324(2), c = 11.155(4) Å, = 71.43(2), = 77.21(2), = 76.40(3)°, triclinic, P1¯ and Z = 2.     

Polymorphism and design of noncentrosymmetric crystals of 4-hydroxybenzaldehyde-4-nitrophenylhydrazone and N′-(2-phenyl-1H-indole-3-aldehyde)-4-nitrophenylhydrazone

The products of crystallization of 4-hydroxybenzaldehyde-4-nitrophenylhydrazone (I) and N′-(2-phenyl-1H-indole-3-aldehyde)-4-nitrophenylhydrazone (II) from different solvents are studied by X-ray diffraction with the aim of examining the polymorphism of hydrazone derivatives. The structural features of the crystals prepared are analyzed. It is shown that, in the case when molecules of organic compounds with a high molecular hyperpolarizability are capable of forming stable acentric supramolecular associates in the crystal, knowledge of their polymorphism offers strong possibilities for designing the noncentrosymmetric crystal structure necessary for a manifestation of the nonlinear optical activity.     

Properties of the Liquid Crystals Formed by the N-Oxides of Certain 4-(4′-pyridyl)phenyl 4″-n-Alkoxybenzoates: Comparison of the N-Oxide and Cyano-groups as Mesogenic Terminal Substituents

The liquid liquid crystal transition temperatures of the N-oxides of certain 4-(4′-pytidyl)phenyl 4″ -n-alkoxybenzoates are reported. The effects on smectic and nematice thermal stability of the N-oxide function and the cyano-group in terminal positions in mesogens are compared and discussed.     

Synthesis,Characterization and Structural Conformation Studies of 2-Amino-3-ethoxycarbonyl-4-(4′-methoxy Phenyl)-4H-pyrano-[3,2-c]-chromene-6-methyl-5-one

2-amino-3-ethoxycarbonyl-4-(4′-methoxy Phenyl)-4H-pyrano-[3,2-c]-chromene-6-methyl-5-one was synthesized by the two-component reaction of 6-methyl-4-hydroxy coumarin with 4′-methoxy-2-cyano cinnamate, which was synthesized by Knoevenagel reaction with 88% yield. The compound obtained was characterized by spectroscopic techniques and confirmed by X-ray crystallographic studies. The crystallographic data analysis reveals that the title compound crystallizes in the triclinic space group \(P\overline{1}\) with cell parameters a = 7.7750(8) Å, b = 9.0310(6) Å, c = 15.6120(17) Å, α = 77.249(7)°, β = 115.860(3)°, γ = 70.139(7)°, V = 1,003.0(16) Å³ for Z = 4. The structure has been solved by direct methods and refined to R1 = 0.0552 for 3,164 observed reflections with I > 2 σ(I). The pyran ring is in a flattened boat conformation. The carbonyl group is oriented in a -synperiplanar(cis) conformation.

Open image in new window

     

The Mesogenic Behavior of Isomeric and Nonisomeric Series of Novel Azoesters. 4-(4′-n-Alkoxy Benzoyloxy) Phenylazo-2″-Bromobenzenes

A novel homologous series: 4-(4′-n-alkoxy benzoyloxy) phenylazo-2^″-bromobenzenes is synthesized and studied with a view to understanding and establishing the effects of molecular structure on mesogenic behavior in a series. The mesogenic property commences from fifth homologue to the last homologue. The transition temperatures of the series are relatively low ranging between 68°C and 143°C. The mesogenic range varies between 6°C and 22°C. The novel azoester series is nematogenic without exhibition of any smectogenic property and an average thermal stability of 89.4°C. The mesogenic behavior of the novel series is compared with structurally similar isomeric/nonisomeric other known series.     

Crystal structure of 4-phenyl-3,5-dioxacyclohexyl-1, 1′-cyclopentane-2′,3″-(1,5,8,11-tetraoxacyclotridecane)

The structure of the title compound is determined by X-ray diffraction (DAR-UMB diffractometer, θ-θ/2θ scan mode, MoK _α radiation, direct method). The crystal is monoclinic, a = 24.582(6) Å, b = 22.812(8) Å, c = 8.647(3) Å, γ = 60.64(2)°, ρ _calcd = 1.232 g/cm³ space group A2/a, and Z = 8 for C₂₂H₃₂O₆. The molecule consists of four fragments: 13-crown-4 (A), 1,3-dioxane (B), a five-membered ring (C) acting as a bridge between fragments A and B, and a phenyl ring (D). Introduction of the bulky ring C as a bridge into the molecule results in significant deviations (up to ±0.014 Å) of the ether O atoms from planarity. The conformation of the macrocyclic fragment is [3433] according to the Dale notation. The C—H?O 1,4-interactions, which are energetically favorable occur in the propylene part of 13-crown-4: the C(2)?O(5) and C(4)?O(1) distances are 2.82 Å. The molecules in the structure form planar networks parallel to the xy plane. The intermolecular contacts correspond to the van der Waals interactions.     

7-Hexyloxy-3-[4’-(3-methylbutyloxy) phenyl]-4H-1-benzopyran-4-one: Study of Smectic behaviour and UV absorption profile

The intermolecular interaction energies between a pair of 7-Hexyloxy-3-[4’-(3-methylbutyloxy) phenyl]-4H-1-benzopyran-4-one (HMBPB) molecules have been estimated with respect to translational and orientational motions. The complete neglect differential overlap (CNDO/S) method has been employed to calculate the net atomic charge and atomic dipole moment components at each atomic center. The modified Rayleigh-Schrodinger perturbation theory along with multicentered-multipole expansion method has been employed to evaluate the long-range intermolecular interactions, while a ‘6-exp’ potential function has been assumed for short-range interactions. The total interaction energy values obtained through these computations have been used to calculate the probability of each configuration at room temperature (300K), and isotropic-smectic transition temperature (412.6K). Molecular arrangements inside a bulk of materials and smectic behavior of the compound in terms of their relative order have been discussed. Translational and rotational rigidity of the molecule has been analyzed to understand the smectic behaviour. The UV absorption profile has been estimated using CNDO/S, and INDO/S methods.     

Crystal and molecular structure of CI Solvent Yellow 18, 4-(2′,4′-dimethyl phenyl hydrazono)-5-methyl-2-phenyl-3H-pyrazol-3-one

The crystal structure of CI Solvent Yellow 18, C₁₈H₁₈N₄O, has been determined by single crystal X-ray diffraction techniques. It crystallizes in the monoclinic system witha=7.480(2) Å,b=19.184(3) Å,c=11.260(1) Å,=98.00(3)°, space groupP2₁/n andZ=4. The structure has been solved by direct methods, and least-squares refinement has been completed on three-dimensional data (2310 reflections, CuK radiation). The hydrogen atoms have been found, but only their positional parameters refined. Final residual 0.085 (all positive intensity data). The molecule exists as the hydrazone tautomer and intramolecular hydrogen bonding keep the molecule approximately planar. The molecules are packed in layers parallel to the (¯202) plane and in columns parallel tob. Alternate molecules within the columns are in antiparallel. The molecules are linked by van der Waals' forces.     

Structural studies of N-2-(3-picolyl)- and N-2-(4-picolyl)-N′-tolylthioureas

Reactions of 2-aminopicolines with 2- and 4-tolyl isothiocyanates yielded N-2-(4-picolyl)-N-4-tolylthiourea, 1, N-2-(3-picolyl)-N-4-tolylthiourea, 2, and N-2-(4-picolyl)-N-2-tolylthiourea, 3. Compound 1 is monoclinic, of space group P2₁/c with a = 7.456(1) Å, b = 13.135(3) Å, c = 13.959(3) Å, = 104.99(3)°, and V = 1320.5(5) ų with Z = 4, for d _calc = 1.294 g/cm³. Compound 2 is triclinic, of space group with a = 6.877(3) Å, b = 7.590(5) Å, c = 13.213(9) Å, = 78.38(2)°, = 77.96(4)°, = 86.36(4)°, and V = 660.5(7) ų with Z = 2, for d _calc = 1.294 g/cm³. Compound 3 is monoclinic, of space group P2₁/c with a = 12.604(2) Å, b = 15.592(3) Å, c = 6.875(2) Å, = 91.05(2)°, and V = 1350.9(2) ų with Z = 4, for d _calc = 1.265 g/cm³. The three thioureas are found in both solid state and solution in a conformation resulting from intramolecular hydrogen bonding. Compounds 1 and 3 present an intermolecular hydrogen bond involving the thione sulfur and the NH hydrogen, which is not present in 2 owing to the steric hindrance of the methyl group in the phenyl ring. The geometry of the molecule is affected by the position of the methyl groups on the pyridine and aryl rings.     

Crystal and molecular structure of 2,6-dimethyl-3-acetyl-5-carbomethoxy-4- (4′-methoxyphenyl)-1,4-dihydropyridine

2,6-Dimethyl-3-acetyl-5-carbomethoxy-4-(4-methoxyphenyl)-1,4-dihydropyridine has been synthesized and characterized by X-ray diffraction analysis. The compound crystallizes in the monoclinic space group P2 ₁/c with cell parameters a=16.085(2) Å, b= 12.332(3) Å, c= 8.479(4) Å, = 99.23(8)°, Z=4. The structure exhibits both intra and intermolecular hydrogen bonds. The structure adopts a flat boat conformation in the dihydropyridine ring.     

Low-temperature study of the molecular and crystal structures of 2-(2′-tosylamino-5′-nitrophenyl)-4H-3,1-benzoxazin-4-one, an organic luminophore

The crystal structure of 2-(2′-tosylamino-5′-nitrophenyl)-4H-3,1-benzoxazin-4-one (I) is studied by X-ray diffraction at 100 K (C₂₁H₁₅N₃O₆S, a = 20.899(2) Å, b = 10.948(1) Å, c = 8.260(1) Å, V = 1889.3(1) ų, Z = 4, and space group Pbn2₁). The compound exhibits an anomalous Stokes shift. Upon cooling, the oxazineaminophenyl fragment of compound I acquires a quinoid structure and the linear parameters of the intramolecular N-H?N hydrogen bond increase (the distance between the heterocyclic nitrogen atom and the hydrogen atom of the tosylamino group becomes 1.92 Å). The complete optimization of the geometry of molecules in compound I and unsubstituted 2-(2′-tosylaminophenyl)-4H-3,1-benzoxazin-4-one in the ground singlet electronic state is performed by the semiempirical method with the MOPAC program. It is shown that the oxygen atoms in the sulfo group of molecule I are nonequivalent, because one of them is involved in the intermolecular C-H?O hydrogen bond.     

Structural study of nitrovinylindoles: (I) 2-methyl-3-(2′-methyl-2′-nitrovinyl)indole and (II) 3-(2′-nitrovinyl)indole

Compound (I) is 2-methyl-3-(2-methyl-2-nitrovinyl)indole, C₁₂H₁₂N₂O₂,M _r=216.24, monoclinic,P2₁/n,a=16.710(1),b=7.627(1),c=17.646(1) Å,=104.8(1)°,V=2174.7(1) ų,Z=8.D _x=1.321 g cm^–3, MoK, =0.71073 Å,=0.858 cm^–1,F(OOO)=912, room temperature,R=0.061 for 1956 observed reflections. Compound (II) is 3-(2-nitrovinyl)indole, C₁₀H₈N₂O₂,M _r=188.18, monoclinic,P2₁/n,a=10.178(1),b=10.608(1),c=8.411(1) Å,=105.5(2)°,V=875.0(1) ų,Z=4,D _x=1.4284 g cm^–3, CuK, =1.5418 Å,=8.068 cm^–1,F(000)=392, room temperature,R=0.040 for 1330 observed reflections. Compounds (I) and (II) have a similar geometry, the only significant difference lying in the rotation of the nitrovinyl chain. This feature could be responsible for the difference in biological activity. In both compounds, the molecules are associated, forming charge-transfer complexes.     

Chain Ordering and Sm-N Transition in Different Members of the Homologous Series 4-(4′- n-AIkoxy Benzylideneamino) Biphenyls

Our extension of Marcelja's theory of nematic-isotropic transition to the smectic A phase is used to calculate the smectic A-nematic (Sm-N) transition temperatures for the homologous series 4–(4′- n-alkoxy benzylideneamino) biphenyls. In a mean field calculation, explicit inclusion of the conformational energies of the alkyl chain of a molecule in the partition function shows an even-odd effect generally observed in experiments on Sm-N transitions. It is found that the members of this series showing the smectic phase will have first order Sm-N transitions and the transition entropies for individual members are calculated.     

X-ray structure investigation of two polymorphic modifications of 1-acetyl-3-(4-nitrophenyl)-5-(2′-furyl)pyrazoline

Two polymorphic modifications of 1-acetyl-3-(4-nitrophenyl)-5-(2′-furyl)pyrazoline (I) are investigated by X-ray diffraction with the purpose of analyzing the factors responsible for the formation of crystal structures of the optical nonlinear organic compounds. Both modifications crystallize simultaneously upon slow evaporation of a solution of compound I in an isopropanol-acetonitrile (3: 1) mixture. It is found that the molecular geometry of the polymorphic modifications is characterized by the rotation of the furan substituent with respect to the plane of the pyrazoline ring. The molecular hyperpolarizabilities (β) of both conformers are calculated.     

Absolute Configuration Determination of Two Optically Active Cyclopropyl-Ketoacids: (1′S, 3S) 3-(2′,2′-Dichloro-1′-methyl-cyclopropyl)-6-oxo-heptanoic acid and (1′S, 3S) 3-(2′,2′-Dibromo-1′-methyl-cyclopropyl)-6-oxo-heptanoic acid

Abstract  

The title compounds C₁₁H₁₆Cl₂O₃ (III) and C₁₁H₁₆Br₂O₃ (IV) have been prepared from (S)-Limonen. Their crystal structure and absolute configuration have been determined by X-ray analysis which confirmed the 1′S absolute configuration at the cyclopropyl moiety, in agreement with the known absolute configuration of the starting material. Both (III) and (IV) are orthorhombic, space group P2₁2₁2₁ with a = 7.2558(4) ? (for III) 7.4058(6) ? (for IV), b = 9.7885(5) ? (for III) 9.7459(7) ? (for IV), c = 17.7551(10) ? (for III) 18.0354(14) ? (for IV), α = 90°, β = 90°, γ = 90° and Z = 4.