The Crystalline state and the Mesophases of Cholesteryl Oleyl Carbonate

The preparation of pure crystalline cholsteryl oleyl carbonate is described. The melting point, the mesophase transition temperatures, and the enthalpy of the melting process are recorded, and a method of maintaining cholesteryl oleyl carbonate in a pure state over extended periods of time is suggested.     

Liquid-Crystalline Solvents as Mechanistic Probes. 10. Dynamics of Intramolecular Quenching of Pyrenyl Fluorescence in the Liquid-Crystalline and Isotropic Phases of a Cholesteric Solvent1

Abstract

The effect of cholesteric order in a 59.5/15.6/24.9 (w/w/w) mixture of cholesteryl oleate/cholesteryl nonanoate/cholesteryl chloride (CM) on the intramolecular fluorescence quenching of l,3-bis(l-pyrenyl) propane (P3P) has been explored. A comparison with fluorescence quenching of N,N-dimethyl-4-[3-(l-pyrenyl)propyl]aniline (P3D) in CM is made. From the Arrhenius activation parameters for quenching in the cholesteric and isotropic phases, it is concluded that the motions which take the ground state conformers of P3P to their quenching transition state are nearly impervious to macroscopic CM mesophase order: in the cholesteric phase, E'_a = 10.5±0.4 kcal mol^?1 and ΔS^? = 1 ± 1 eu; in the isotropic phase, E'_a = 10.0 ± 0.2 kcal mol^?1 and ΔS^? = 0 ± 0.5 eu. An explanation of these results is advanced.     

Optical Rotatory Power of a Cholesteric Liquid Crystal for Obliquely Incident Light Using Multiple Scaling

The axis of polarization of light propagating through a cholesteric liquid crystal rotates with the angular rotation per distance traversed termed rotatory power. The rotation is due to the helical array of the molecules rather than due to the individual molecules as is found, for instance, with light being propagated through a sugar solution. The De Vries model for rotatory power of a cholesteric liquid crystal is generalized using multiple scaling theory to include light traveling at an oblique angle to the pitch axis. The resulting expression is tested experimentally using a mixture of cholesteryl oleyl carbonate and cholesteryl chloride.     

NMR Studies of (TMTSF)2PF6

Abstract

Pulsed NMR determinations of the relaxation times T₂, T₂* and T₁, as a function of temperature and field, for the methyl group protons in (TMTSF)₂PF₆ are reported. Below the metal-insulator transition (T_MI)T₂* shortens while T₂ increases, indicating a line which is inhomogeneously broadened due to the onset of a SDW. The SDW also contributes to the spin-lattice relaxation rate, T₁ ^?1, in the neighborhood of T_MI. A frequency dependent maximum in T₁ ^?1 is observed near 20K and is attributed to methyl group rotation. A frequency independent maximum at 58K suggests a structural phase transition involving rearrangement of the methyl and PF₆ groups.     

Synthesis, crystal structures, and properties of copper complexes with tripodal ligands and azide anion

Two new Cu^II complexes, (CuL¹N₃)ClO₄ (1) and (CuL²N₃)ClO₄ (2), have been synthesized and characterized in the presence of NaN₃, where L¹ = tris[2-(6-methylpyridyl)methyl]amine and L² = tris[(3,5-dimethylpyrazol-l-yl)methyl]amine, and their crystal structures have been determined by X-ray diffraction methods. Compound 1 crystallizes in the triclinic space group P–1, with a = 8.258(2) Å, b = 11.481(2) Å, c = 14.158(3) Å, = 72.30(3)°, = 79.05(3)°, = 86.08(3)°, V = 1255.4(5) ų. Compound 2 crystallizes in the monoclinic space group C2/c, with a = 26.752(2) Å, b = 10.561(2) Å, c = 21.059(4) Å, = 120.51(3)°, V = 5126(3) ų. In both compounds, each Cu^II center is in a distorted trigonal–bipyramidal coordinated environment with four nitrogen atoms from the tripodal ligand and one nitrogen atom from the azide group. The coordination geometry around Cu^II center of 1 is axially compressed trigonal bipyramid, while that of 2 is an axially elongated trigonal bipyramid. The coordinated azide group is in the axial site in both complexes. A quasi-dimeric structure of 1 has been formed in the unit cell through hydrogen bonding. The electronic spectra of two complexes in solution have been further studied by UV–vis technique, and the coordination properties have been discussed.     

1-[2-(p-Tolyl)-1-diazenyl]-3-({3-[2-(p-tolyl)-1-diazenyl] perhydrobenzo[d]imidazol-1-yl}methyl)perhydrobenzo[d]imidazole: synthesis,characterization and X-ray crystal structure

1-[2-(p-Tolyl)-1-diazenyl]-3-({3-[2-(p-tolyl)-1-diazenyl]perhydrobenzo[d]imidazol-1-yl}methyl)perhydrobenzo[d]imidazole(1) has been synthesized by reactionof a mixture of 1,2-diaminocyclohexane and formaldehyde withp-toluene diazonium chloride inaqueous solution. The product has been characterized by IR and NMRspectroscopy and elemental analysis. A crystal grown from solution ina mixed solvent system of ethyl acetate and hexanes was analyzed byX-ray crystallography. The solution of the crystal structure of(1) is important in establishing theconnectivity of this molecule and other compounds of similarstructure. The crystal structure of (1) is compared with the previously reportedstructure of the p-cyano analogue(2). Compounds (1) and (2)differ principally in the relative orientation of the heterocyclicrings; in (1), the molecule has adistinct V-shape, whereas compound (2) adopts a more extended conformation.Significant conjugation within the triazene moieties is evident inboth (1) and (2), as manifested in the N465=N andN–N bond lengths. The conjugation is greater in (2) due to the extended conjugation through tothe nitrile group. The title compound (1){C₂₉H₄₀N₈}crystallizes in the monoclinic, space group C2/c, with lattice constants: a = 30.532(6) ?,b =5.9050(12) ?, c= 15.463(3) ?, α = 90°,β = 99.94(3)°, γ = 90°,V =2746.0(10) ?³, Z = 4, D _c =1.209 mg m⁻³,F(000) = 1076, R ₁ = 0.0785,wR ₂= 0.1877.     

Thermal Analysis,Quantum Chemical Calculations,and Structural Characterization by Single Crystal Synchrotron Radiation of a Monoclinic Polymorph of Citraconic acid

Abstract  

The crystal structure of a monoclinic polymorph of methyl maleic acid (citraconic acid, polymorph II) was determined using single crystal synchrotron data from a small fragment extracted from the reagent bottle. The material crystallizes in space group P2₁/c with unit cell parameters a = 8.109(2), b = 7.090(2), c = 10.709(3) ?, β = 114.148(16)°, V = 561.8(3) ?³, Z = 4, d _c = 1.538 g cm⁻³. In this polymorph, the carboxylic group with the α-methyl group participates in cyclic hydrogen bonds with graph set symbol R₂² (8) R_{2}^{2} (8) , while the other carboxylic group participates in a hydrogen bonding pattern represented by the C(4) graph set symbol. In contrast, in a previously reported polymorph (polymorph I) obtained by slow evaporation from ethyl acetate, both carboxylic groups participate in cyclic hydrogen bonding motifs. Thermal analysis suggests that the transformation of polymorph II into polymorph I is monotropic.     

Synthesis,Spectroscopic Studies and Structure of 2-[(Benzo[<Emphasis Type="Italic">d</Emphasis>]thiazol-2-ylamino)methyl]phenol

Abstract  

Schiff base (E)-2-[(benzo[d]thiazol-2-ylimino)methyl]phenol (1) has been synthesized from the reaction of 2-hydroxy-benzaldehyde with 2-aminobenzothiazole. The 2-[(benzo[d]thiazol-2-ylamino)methyl]phenol (2) was prepared reduction of the Schiff base 1 with sodium borohydride. The compounds 1 and 2 have been characterized by elemental analysis, FT-IR, ¹H-NMR, ¹³C-NMR and UV–visible spectroscopic techniques. The structure of the compound 2 has also been examined crystallographically. The compound 2 crystallizes in the monoclinic space group P2/c. The unit cell parameters were found as a = 10.017(1), b = 11.725(1), c = 10.341(1) ?, V = 1208.1(1) ?³, D _x = 1.409 g cm⁻³ and Z = 4. The crystal structure was solved by direct methods and refined by the full-matrix least squares method and found as R ₁ = 0.0308 and wR ₂ = 0.0818 for 2032 for the observed reflections [I > 2σ(I)].     

Optical Effects and Molecular Ordering in Spherulites

The optical behaviour of spherulite textures exhibited by mixtures of cholesteryl acetate and cholesteryl ethyl carbonate is investigated. The observed optical effects arise due to a helicoidal arrangement of the molecules along the radial directions of the spherulites, the long axes of the molecules being oriented transverse to the radial directions. The helicoidal nature of the structure is strikingly demonstrated by two sensitive interference experiments wherein sinusoidal interference fringes are observed. The observed results are in agreement with the theory developed for the interference effects.     

Synthesis and structure of tris[2-(1-naphthalenyloxy)ethyl]amine and tris[2-(1-naphthalenyloxy)ethyl]amine perchlorate

Syntheses and crystal structures of tris[2-(1-naphthalenyloxy)ethyl]amine 1 and tris[2-(1-naphthalenyloxyl)ethyl]amine perchlorate 2 are reported. Compound 1 crystallizes in the rhombohedral system, space group R3¯ with a = 13.077(4), c = 29.011(8) Å, and D _calc = 1.233g/cm³ for Z = 6; compound 2 crystallizes in the cubic system, space group P2₁3 with lattice parameters a = 14.630(5) Å and D _calc = 1.332g/cm³ for Z = 4. In 1, three naphthalene rings make dihedral angles of 109.21, 70.78, 70.78,° respectively. In 2 they make dihedral angles of 107.3, 72.7, 72.7° respectively. Deviation of N from the plane (C(12),C(12)i,C(12)ii) in 1 is 0.3742 Å which is less than that in (2) (–0.4223 Å). The crystals structure is stabilized by van der Waals interactions in both compounds.     

Infrared Spectroscopic Studies of the Nematogenic Homologous Series p−(p−ethoxyphenylazo) phenyl alkanoates

Abstract

Infrared (500–2000 cm^?1) spectra of p-(p-ethoxyphenylazo)phenyl alkanoates (valerate, hexanoate, heptanoate and undecylenate) have been examined in the solid state. An attempt has been made to correlate the variations in the intensities and frequency shifts with the known crystal structures determined by X-ray diffraction methods. The gradual shift towards smaller wavelength in the carbonyl (C=O) stretching frequency and the relative increase in the intensity of the carbonyl frequency as the chainlength increases may be correlated with the increased deviation from planarity of the molecule.     

An X-ray Crystallographic Study of the Related Triazenes, 1,4-Di[(<Emphasis Type="Italic">E</Emphasis>)-2-(2-nitrophenyl)-1-diazenyl]piperazine and Methyl 4-{(E)-2-(4-methylpiperazino)-1-diazenyl}benzoate

Abstract The crystal structures of methyl 4-{(E)-2-(4-methylpiperazino)-1-diazenyl}benzoate (2a) and 1,4-di[(E)-2-(2-nitrophenyl)-1-diazenyl]piperazine (3a) have been determined by single crystal X-ray diffraction analysis. The bis-triazene (3a) adopts an unusual pseudo-boat conformation in the piperazine ring, with a dihedral angle of 52.20(0.06)° between the two planes defined within the piperazine ring. The crystal structures of 2a and 3a are compared with the structure of the triazene (4) and the closely related bis-triazene (5). The piperazine ring of 2a adopts a typical chair conformation, whereas the piperazine ring of 3a adopts an unusual boat conformation. Crystal data: 2a C₁₃H₁₈N₄O₂, monoclinic, space group P2₁ /n, a = 13.849(3) ?, b = 6.577(1) ?, c = 14.904(3) ?, α = 90°, β = 96.098(3)°, γ = 90° and V = 1,349.8(4) ?³, for Z = 4. 3a C₁₆H₁₆N₈O₄, triclinic, space group P-1, a = 7.6066(6) ?, b = 8.3741(7) ?, c = 14.507(1) ?, α = 78.673(1)°, β = 81.877(1)°, γ = 73.445(1)° and V = 865.0(1) ?³, for Z = 2. Index abstract The crystal structures of methyl 4-{(E)-2-(4-methylpiperazino)-1-diazenyl}benzoate (2a) and 1,4-di[(E)-2-(2-nitrophenyl)-1-diazenyl]piperazine (3a) have been determined by single crystal X-ray diffraction analysis.     

Molecular Packing Coefficients of the Homologous Series Cholesteryl Alkanoates

The properties of cholesterol derivatives are important owing to the involvement of these compounds in a myriad of industrial and biological research areas such as thermography, display devices and the formation in atherosclerosis of arterial deposits containing cholesteryl esters. Molecular structural studies of mesogens in the crystalline state have been carried out in search of a better understanding of the physical properties which lead to mesophase formation. It has been demonstrated previously for a homologous series of nematogens¹ how the molecular packing coefficients of the solid phase vary with increasing chain length and how this throws light upon the variation of other physical properties. Here, we extend this treatment to the cholesteryl alkanoates. Detailed crystal structure analysis is available for only one member of this series: cholesteryl tetradecanoate, which was studied by Craven and de Titta.² Prior to this, unit cell dimensions and space groups has been obtained for 13 members by Barnard and Lydon.³ They found the crystallography of these compounds to be complex. No overall homology of crystal structure was apparent and at least eight different types of crystal structure occur.     

Crystal Structure of Diethyl[(4chlorophenyl)(dibenzylamino)methyl]propanedioate

Abstract  

The titled new functionalized N,O,O-ligand of type diethyl[(4-chlorophenyl)(dibenzylamino)methyl]propanedioate (4) is prepared in good yield through condensation of dibenzylamine, with 2-arylidene-malonic acid diethyl esters 3. The structure of 4 was determined by spectral (IR, ¹H NMR), elemental analyses and X-ray diffraction data. The molecular conformation shows two possible pockets ready to coordinate two metal atoms.     

The Synthesis and Crystal Structure of 5-(4-Bromophenylamino)-2-methylsulfanylmethyl-2<Emphasis Type="Italic">H</Emphasis>-1,2,3-triazol-4-carboxylic Acid Ethyl Ester

Abstract  The 5-(4-bromophenylamino)-2-methylsulfanylmethyl-2H-1,2,3-triazol-4-carboxylic acid ethyl ester 6 was synthesized from p-bromoaniline. The yielded product 6 was investigated with X-ray crystallographic, NMR, MS, and IR techniques. Compound 6, C₁₃H₁₅BrN₄O₂S, Mr = 371.26, crystallizes in the monoclinic space group P2₁/n with unit cell parameters a = 5.5220(1), b = 26.996(5), c = 10.596(2) ?, β = 103.83(3). V = 1533.8(5) ?³, Z = 4, Dx = 1.608 mg m⁻³. The final R ₁ was 0.0844; wR ₂ was 0.1560. H-bond is discussed. Index Abstract  The structure of 5-(4-bromophenylamino)-2-methylsulfanylmethyl-2H-1,2,3-triazol-4-carboxylic acid ethyl ester from 5-amino-1-(4-bromophenyl)-1,2,3-triazol-4-carboxylic acid ethyl ester is studied. H-bond is discussed.      

Synthesis and crystal structures of the bis-Schiff bases of 2-(methylthio)aniline with isophthaldehyde, terephthaldehyde, and para-diacetylbenzene

The crystal structures of the new compounds 1,3-bis(((2-methylthio)phenylimino)methyl)benzene (1), 1,4-bis(((2-methylthio)phenylimino)methyl)benzene (2), and 1,4-bis(1-((2-methylthio)phenylimino)ethyl)benzene (3) were obtained by single crystal X-ray diffraction. Compound 1 crystallizes in the orthorhombic space group Pna2₁ with a=16.8250(13) ?, b=18.1068(13) ?, c=6.3086(5) ?; and Z=4. Compound 2 crystallizes in the triclinic space group with a=6.7532(7) ?, b=9.4433(9) ?, c=15.2473(15) ?; and α=86.339(2)°, β=80.609(2)°, γ=80.962(2)°; and Z=2. Compound 3 crystallizes in the triclinic space group with a=6.787(3) ?, b=7.517(3) ?, c=10.653(4) ?; and α=89.998(7)°, β=72.341(7)°, γ=75.998(7)°; and Z=1. Details of the synthesis, structures, and spectroscopic results are discussed.     

Synthesis and Crystal Structures of Copper(II) Complexes Derived from 5-Methoxy-2-[(2-morpholin-4-ylethylimino)methyl]phenolate and (2-Morpholin-4-ylethyl)-(1-pyridin-2-ylethylidene)amine

Abstract  

A pair of copper(II) complexes, [CuL¹(ONO₂)(OH₂)] 1 and [CuBrL²N₃] 2, where L¹ is 5-methoxy-2-[(2-morpholin-4-ylethylimino)methyl]phenolate, and L² is (2-morpholin-4-ylethyl)-(1-pyridin-2-ylethylidene)amine, have been synthesized and characterized by elemental analysis, IR spectra and single crystal X-ray diffraction. Complex 1 crystallizes in the monoclinic space group P2₁/c, with a = 10.496(2), b = 19.113(3), c = 8.586(2) ?, β = 105.186(10)°. Complex 2 crystallizes in the monoclinic space group C2/c, with a = 16.606(3), b = 7.357(2), c = 26.043(5) ?, β = 94.996(2)°. The Cu atom in each complex is five-coordinate in a square pyramidal geometry.     

Imidazolium chloride organophosphate antidotes

The structures of four imidazolium oxime derivatives were solved by direct methods. These compounds have been shown to be effective in the treatmen of organophosphate poisoning. Despite substantial differences in the nature of the substituent on N1, all four compounds have similar shapes when viewed down the plane of the imidazole ring. The potency of these compounds in the treatment of organophosphate poisoning correlates well with the distance between the imidazole ring and the oxygen moiety on the side chain. 2-(hydroxyimino)methyl-3-methyl-1-[1-(3-methyl-sulfonylpropyloxy) methyl]imidazolium chooride (1) crystallizes in the triclinic space groupPī (Z=2). The unit cell parametersa, b, c (?) and α, β, and γ (^o) were: 8.506(2), 8.787(4), 10.070(4), 73.68(3), 81.37(3), 85.39(3). 2-(hydroxyimino)-methyl-3-methyl-1-(2′-N-phenylsulfonylamino-1′-ethyl) imidazolium chloride (2) crystallizes in the monoclinic space groupP2 ₁ la(Z=4). The unit cell parametersa, b, c (?) and β (^o) were: 12.690(2), 6.317(4), 20.193(4), 91.47(2). 1-(2′-ethyl-2′-trifluoromethanesulfonyl-aminoethyl)-2-(hydroxyimino) methyl-3-methylimidazolium chloride (3) crystallizes in the triclinic space groupPī (Z=2). The unit cell parametersa, b, c (?) and α, β, and γ (^o) were: 6.635(1), 11.333(2), 12.274(3), 115.05(3), 98.46(3), 90.11(3). 2-(hydroxyimino)-methyl-3-methyl-1-[2-(2-methyl-3-nitrobutyloxy) methyl]-imidazolium chloride (4) crystallizes in the orthorhombic space groupP2₁2₁2₁ (Z=4). The unit cell parametersa, b, andc (?) were: 10.034(1), 11.401(2), 13.352(2).     

Dielectric secondary relaxation and phenylene ring dynamics in bisphenol-A polycarbonate

A detailed dielectric investigation of the secondary relaxation on a series of bisphenol-A polycarbonate samples with different treatments that influence the local polymer structure is presented. Dielectric spectroscopy measurements were performed in the frequency range 10⁻²–10⁶ Hz. The structural changes induced by different thermo-mechanical treatments, as well as by polymer crystallization, lead to a reduction of the dielectric losses that is not uniform over the whole frequency range but more pronounced in the high frequency side of the γ-relaxation peak. These effects have been rationalized in terms of the great coupling between the motions of the phenylene rings and those of the dipolar entity of the repeating unit (namely the carbonate group). Furthermore, it is shown that the same approach allows rationalizing the marked differences between the dielectric and mechanical secondary relaxations.     

Crystal Structure and Characterization of [Ni(RPOEt)<Subscript>2</Subscript>(C<Subscript>2</Subscript>H<Subscript>5</Subscript>OH)<Subscript>2</Subscript>](ClO<Subscript>4</Subscript>)<Subscript>2</Subscript> [RPOEt = bis{(diphenylphosphinyl)methyl}ethyl phosphinate]

Abstract  

The compound [Ni(RPOEt)₂(C₂H₅OH)₂](ClO₄)₂ (1) [RPOEt = bis{(diphenylphosphinyl)methyl}ethyl phosphinate] has been prepared in the form of single crystals and characterized by elemental and thermal analyses, IR spectroscopy and by a single crystal X-ray diffraction study. The complex crystallizes in the triclinic P[`1] P\bar{1} space group with a = 9.8773(5), b = 13.741(1), c = 14.287(1) ?, α = 64.313(9), β = 70.280(5), γ = 89.973(7)o, V = 1620.5(2) ?³, and Z = 1. The nickel(II) atom in 1, situated at the centre of symmetry, is coordinated by four oxygen atoms from two RPOEt ligands and two oxygen atoms from two ethanol molecules in a slightly distorted octahedral environment. The third phosphoryl-oxygen atom from the phosphinate ligand is hydrogen bonded to the oxygen atom of the ethanol molecule coordinated to nickel(II). The complex [Ni(RPOEt)₂(C₂H₅OH)₂]²⁺ cations are linked by the C–H···O hydrogen bonds into one-dimensional chains and by the composite π···π and C–H···π phenyl interactions into a final three-dimensional structure.