Synthesis and Mesomorphic Properties of the Homologous Series of Di-(4′- n-alkylphenyl)- trans-cyclohexane-1,4-dicarboxylates

The homologous series of di-(4′- n-alkylphenyl)- trans-cyclohexane-1,4-dicarboxylates in which the alkyl group is C₁-C₁₂ has been prepared by esterification of trans-1,4-cyclo-hexanedicarboxylic acid or dicarbonyl chloride with 4-alkylphenols. Mesomorphic properties and phase transitions as determined by hot-stage polarizing microscopy and DSC are discussed in relationship to various structural features. Comparisons of these properties with those for the corresponding alkoxy series and the analogous terephthalic acid diesters are also presented and discussed.     

Structure of the α-(allcis) form of 2,4,6-tris(trichloromethyl)-1-oxa-3,5-dithian

The higher-melting (mp 236°C)-isomer of dithioparachloral, i.e.,-2,4,6-tris(trichloromethyl)-1-oxa-3,5-dithian, is orthorhombic,Pnma,a=9.983(2),b=15.318(2),c=10.416(2) Å,V=1592.81 ų,Z=4. The structure was solved by direct methods, from data collected at room temperature on an Enraf-Nonius CAD4 diffractometer, and refined by least-squares to a finalR value of 0.040 using 1017 reflections. The molecule is in the chair conformation with all threecis-CCl₃ groups located pseudoequatorially. Endocyclic parameters are: torsion angles (deg) C-O-C-S 75.1(3), O-C-S-C –63.2(3), C-S-C-S 62.4(3); angles (deg) C-O-C 111.9(2), O-C-S 112.6(3), C-S-C 94.8(2), S-C-S 113.2(1); bond lengths (Å) O-C 1.426(5), C-S 1.824(4), S-C 1.818(3) (quoted in cyclic order).     

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.     

Investigation of the structure and properties of (K x (NH4)1 − x )3H(SO4)2 single crystals

The influence of isomorphous replacement in the cation sublattice on the kinetics of the phase transition in single crystals of the solid solutions (K _x (NH₄)_{1 ? x} ) _m H _n (SO₄)_{(m + n)/2} · yH₂O belonging to the K₃H(SO₄)₂-(NH₄)₃H(SO₄)₂-H₂O salt system was studied. Superproton phase transitions for the end compositions of this system have been found earlier. The optical and thermal properties of crystals with the composition (K,NH₄)₃H(SO₄)₂ in the temperature range from 295 to 500 K were investigated, and the crystal structure was determined at 295 K. The results of the study and the comparison with the literature data show that the replacement of potassium atoms with ammonia leads to a fundamental change in the kinetics of the phase transition, the phase-transition temperature remaining virtually unchanged.     

Crystal structure of (4α,4aα,8aα)-(±)-octahydro-2-(phenylmethyl)-2H-1,2-benzoxazin-4-ol, 4-methylbenzenesulfonate(ester)

The title compound, a bicyclic tetrahydro-1,2-oxazine, crystallizes in a monoclinic lattice, space group P2₁/c, with a = 12.9809(18)Å, b = 12.920(2)Å, c = 13.631(2)Å, = 110.713(12)°, and Z = 4. The structure found in the solid state for this conformationally mobile molecule shows the tosyl group in an axial position and a benzyl group in an equatorial position of the bicyclic system.     

Crystal Structure of 3′-(4-Methoxyphenyl)-2-Phenyl-4′-(4-Ethoxyphenyl)-1,2-Dihydro-4H,4′H-Spiro [Isoquinoline-3,5′-Isoxazol]-4-One

The title compound, 3′-(4-methoxyphenyl)-2-phenyl-4′-(4-ethoxyphenyl)-1,2-dihydro-4H,4′H-spiro[isoquinoline-3,5′-isoxazol]-4-one was synthesized from the reaction of dipolarophile with p-methoxybenzadoxime in the presence of sodium hypochlorite in chloroform solution. The structure of the synthesized compound was determined by IR, ¹H NMR, mass spectroscopic data, ¹³C NMR spectroscopy, elemental analysis and X-ray crystallography. The structure was solved in monoclinic, space group C2/c with a = 21.941 (4), b = 17.233 (3), c = 15.404 (3) Å, β = 122.193 (2), V = 4928.9 (16) Å³, Z = 8 and with R_int = 0.154. The geometry of the title compound showed that the piperidine ring adopts a half-chair conformation. In the crystal structure, molecules are linked by C–H···O and C–H···N contacts. Weak C–H···π interactions plays an important role in stabilizing the supramolecular structure.     

A comparison of the crystal structures of (dabcoH2)CuCl4 and (dabcoH2)CuCl4⋅H2O

The crystal structures of the anhydrous and monohydrated (dabcoH₂)CuCl₄nH₂O salts (n = 0,1) have been determined and a comparison of their crystal structures has been reported. The anhydrous salt is monoclinic P2₁/c with a = 9.045(2) Å, b = 6.9270(10) Å, c = 18.767(4) Å and = 90.07(3)° with V = 1175.8(4) ų. The hydrated salt is also monoclinic P2₁/c with a = 9.266(2) Å, b = 9.395(2) Å, c = 14.386(3) Å and = 93.32(3)° with V = 1250.3(5) ų. The structures of the two salts are closely related. Both compounds contain isolated distorted (compressed) tetrahedral CuCl₄ ^2– anions, diprotonated dabco cations, and in the case of the hydrated salt, lattice H₂O molecules. In the anhydrous salt, each of the two N–H⁺ groups of the dabcoH₂ ²⁺ dications form bifurcated hydrogen bonds to chloride ions on adjacent CuCl₄ ^2– anions along the c axis, thus forming chains running parallel to the c axis. In the hydrated salt, a water molecule is inserted into one of the pair of bifurcated hydrogen bonds, forming instead N–H O–H CuCl₄ ^2– linkages. The chains thus formed are cross-linked by O–H Cl hydrogen bonds between the chains. Because of this additional hydrogen bonding, the CuCl₄ ^2– anions in the hydrated salt are distorted further from tetrahedral geometry.     

On the stereochemistry of lignin model compounds of the arylglycerol-β-aryl ether type: Crystal structure oferythro-1-(4-hydroxy-3,5-dimethoxyphenyl)-2-(4-hydroxymethyl-2,6-dimethoxyphenoxy)-1,3-propanediol,C20H26O9

The crystal structure of erythro-1-(4-hydroxy-3,5-dimethoxyphenyl)-2-(4-hydroxymethyl-2,6-dimethoxyphenoxy)-1,3-propanediol, C₂₀H₂₆O₉, has been determined from single-crystal X-ray diffraction data. The compound crystallizes in the triclinic space groupP¯1 witha=8.705(6),b=8.893(5),c=13.211(8) Å,=106.23(5),=93.71(5), =82.97(5)° andZ=2. The structure was solved by direct methods. Full matrix least-squares refinement of 366 structural parameters gaveR=0.039 for 1402 observed [I>3a(I)] reflexions. The molecules are held together by van der Waals forces and moderately strong hydrogen bonds. Average bond distances: C(sp ²)-O 1.370(6) Å and C(sp ³)-O 1.426(14) Å.     

The Metabolemeter III: Phase Behaviour Under Pressure of bis-(4-4′-n-Heptyloxybenzylidene)- 1, 4-Phenylenediamine and Terephthalylidene-bis-(4-n-Decylaniline)

By using a metabolemeter, the phase transitions of bis-[4, 4′-n-heptyloxybenzylidene]-1, 4 phenylenediamine (HBPD) and terephthalylidene-bis-[4-n-decylaniline] (TBDA) have been studied. The weakly first order phase transitions (S_G-S_F and S_F-S_I) and the narrowly separated phase transitions (S_C-S_A and S_A-I) of TBDA are detectable. For HBPD, both transitions S_G-S_I and S_I-S_C are individually observed and the enthalpy changes are deduced from pressure increments at the tranformations: two triple points are detected, one directly by a change of slope in the drawing of the equilibrium curves. The pressure-temperature phase diagrams are given; for each transiton, the volume increases on increasing the temperture.     

Synthesis and structure of (±)-4-O-methanesulfonyl-myo-inositol 1,3,5-orthoformate

Racemic 4-O-methanesulfonyl-myo-inositol 1,3,5-orthoformate was prepared by methanolysis of racemic 2,4-di-O-benzoyl-4-O-methanesulfonyl-myo-inositol 1,3,5-orthoformate, in the presence of triethylamine. The diol crystallizes in space group P2₁2₁2₁ with cell dimensions a = 6.094(1), b = 6.502(2), c = 25.947(3) Å, V = 1028.1(4) Å, Z = 4. The molecular crystals show both intra- and intermolecular O—H···O short contacts. The methine and the methyl hydrogens are involved in several C—H···O interactions.     

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.     

Study of the Phase Situation in 4-n-pentylphenyl-4′-n-heptyloxythiobenzoate (7S5)

Results of measurements of the specific heat of 4-n-pentylphenyl-4′-n-heptyloxythiobenzoate in the temperature range from about 90 K to about 370 K are presented. They were carried out with an adiabatic calorimeter, a differential scanning calorimeter and a polarizing microscope. Adiabatic calorimetry revealed four anomalies in the specific heat vs. temperature curve viz., two associated with transitions in the solid phase, one with melting and one with the liquid-crystalline nematic-to-isotropic phase transition. Also, two modifications of the solid, stable and metastable, were found to exist. In addition, the DSC method applied in the 285 K to 370 K range revealed a smectic C phase, but only when the sample is being cooled. The polarizing microscope showed the structural polymorphism of the solid phase in the 297 K to 327 K range to be more complex than would stem from adiabatic calorimetry and DSC measurements alone. It also confirmed the occurence of the S_c phase on cooling as ascertained by the DSC method.     

Supramolecular structure of tetrakis-μ-(4-chloro-3-nitrobenzoato)-bis(methanol)dicopper(II)

The title compound, [Cu₂(II)(4-Cl-3-NO₂–C₆H₃CO₂)₄(CH₃OH)₂] or [Cu₂(4-chloro-3-nitrobenzoate)₄(MeOH)₂] has been prepared and its structure determined using X-ray crystallography. The complex crystallizes in the triclinic space group P-1 with a = 9.6887(9)Å, b = 10.6448(9)Å, c = 11.4194(10)Å, = 108.094(2), = 110.682(2), = 105.055(2), V = 952.691(15)ų, and Z = 1. The structure consists of centrosymmetric dimers in which the Cu(II) atoms display a square pyramidal CuO₅ coordination, with four carboxylate O atoms in the basal plane [CuO 1.951(2)–1.968(2)Å] and the methanol O atoms in the apical position [CuO 2.170(2)Å]. The Cu atoms are 2.614(1)Å apart and are bridged by four benzoate groups. The discrete dimers are extended into 1D chains that result from hydrogen bonding between the coordinated methanol on one Cu(II) dimer and the nitro substituent on an adjacent Cu(II) dimer. The chains are interdigited and held by – stacking interactions forming 3D supramolecular array.     

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.     

Crystal structure of the Λ-[4M] enantiomer of cis-diaqua-bis(1,3-dimethylpteridine-2,4(1H,3H)-dione-N5,O4) copper(II) perchlorate monohydrate

Single-crystal X-ray diffraction studies have been performed on the complex cis-diaqua-bis(1,3-dimethylpteridine-2,4(1H,3H)-dione-O⁴,N⁵) copper(II) perchlorate monohydrate, [Cu(DLM)₂(H₂O)₂](ClO₄)₂ · H₂O. This compound crystallizes in the orthorhombic system, P2₁2₁2₁ space group, Z = 4 with a = 8.749(1) Å, b = 14.213(1) Å, c = 21.200(2) Å, and V = 2636.2(4) ų. The metal ion is surrounded in octahedral geometry by two mutually quasi-perpendicular N5,O4-coordinated lumazine chelators with the O4 atoms trans and the N5 atoms cis. The polyhedron is completed by two cis-coordinated water molecules. The absolute configuration of the complex can be described, following Bailar's nomenclature, as the enantiomer of the stereoisomer 4M. A three-dimensional hydrogen-bond network is defined by water molecules, perchlorate anions, and the O2 of the pteridine A.     

Synthesis and mesomorphic properties of 2,4-bis(4′-n-pentyloxybenzoyloxy)- benzylidine-4″- n-alkoxyaniline

The synthesis and mesomorphic properties of a new series of 2,4-bis(4′-npentyloxybenzoyloxy)- benzylidine-4″ -n-alkoxyaniline (DC5An) are reported. The molecular structure of compounds was confirmed by FTIR, ¹H-NMR, ¹³C-NMR, mass spectroscopy and elemental analysis. The mesomorphic properties were studied by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM) measurements. All compounds of the series exhibit nematic (N) and smectic C (SmC) phases. The first four homologues (DC5A1-DC5A4) display a N mesophase, whereas the highest homologues (DC5A5-DC5A10) exhibit an enantiotropic dimorphism N and SmC phases. The mesomorphic properties of the present series are compared and discussed with other structurally related series.     

Reaction of the dicobalt alkyne compound Co2(CO)6(μ-dmad) with the diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd). Spectroscopic properties, X-ray diffraction data, and thermal reactivity of the chelating isomer of Co2(CO)4(bpcd)(μ-dmad)

Treatment of Co₂(CO)₆(-dmad) (where dmad = dimethyl acetylenedicarboxylate) with the bidentate ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) in the presence of added Me₃NO affords the new alkyne compound Co₂(CO)₄(bpcd)(-dmad) in good yield. Both IR and ³¹P NMR spectroscopies indicate that the bpcd ligand is coordinated to a single cobalt center in a chelating fashion in solution. The solid-state structure of Co₂(CO)₄(bpcd)(-dmad) is identical to the solution structure Co₂(CO)₄(bpcd)(-dmad), as determined by X-ray diffraction analysis. Co₂(CO)₄(bpcd)(-dmad) crystallizes in the triclinic space group P-1, a = 10.7460(8) Å, b = 11.628(2) Å, c = 15.077(1) Å, = 95.831(9)°, = 91.205(7)°, = 101.526(9)°, V = 1834.7(3) ų, Z = 2, and d _calc = 1.514 g/cm³; R = 0.0489, R _w = 0.0528 for 2854 reflections with I > 3(I). The thermal reactivity of Co₂(CO)₄(bpcd)(-dmad) has been briefly explored by spectroscopic methods, and evidence is presented for the attack of one of the PPh₂ groups on an alkyne carbon atom in Co₂(CO)₄(bpcd)(-dmad) to from the zwitterionic hydrocarbyl compound Co₂(CO)₄(-²:²:¹:¹-(MeO₂C)=C(CO₂Me)PPh₂C=C(PPh₂)C(O)CH₂C(O)] upon thermolysis. The redox chemistry of both Co₂(CO)₄(bpcd)(-dmad) and Co₂(CO)₄[-²:²:¹:¹-(MeO₂C) C=C(CO₂Me)PPh₂C=C(PPh₂)C(O)CH₂C(O)] has been explored by cyclic voltammetery.     

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.     

Novel manganese(III) oxidation chemistry: X-ray crystal structures of (1α,2α,4β)-1,2-diacetoxy-4-(4-methoxyphenyl)-6-methoxy-1,2,3,4-tetrahydronaphthalene (compound A) and (1α,2α,4β)-1,2-diacetoxy-4-(2-methoxyphenyl)-8-methoxy-1,2,3,4-tetrahydronaphthalene (compound B)

CompoundA is (1,2,4)-1,2-diacetoxy-4-(4-methoxyphenyl)-6-methoxy-l,2,3,4-tetrahydronaphthalene, C₂₂H₂₄O₆,M _r=384.43, monoclinic, P2₁/n, witha=11.074(3),b=10.353(4),c=17.616(4)Å,=94.96(2)°,V=2012.1ų,D _calc=1.27 g cm^–3 and=0.55 cm^–1 forZ=4. Least-squares refinement of 1371 observed [F ₀5 (F ⁰)] reflections led to the final agreement index ofR=0.052. A twofold disorder was observed for the 1-acetoxy group whereas the 2-acetoxy group was ordered. CompoundB, (1,2,4)-1,2-diacetoxy-4-(2-methoxyphenyl)-8-methoxy-l,2,3,4-tetrahydronaphthalene, C₂₂H₂₄O₆,M _r=384.43, crystallizes in the monoclinic space group, P2₁/c, witha=16.209(2),b=10.076(1),c=13.357(4)Å,=111.41(2)°,V=2030.9ų,D _calc=1.26 g cm^–3 and=0.54 cm^–1 forZ=4. A final agreement index ofR=0.045 was realized by least-squares refinement of 1486 observed [F _o5 (F _o)] reflections. Intermolecular interactions in the cell lattices of compoundsA andB are noted. The title compoundsA andB were prepared by manganese(III) acetate oxidative dimerization of two molecules of 4-methoxystyrene and 2-methoxystyrene, respectively.