Crystal Structures and Phase Transformations of the Fluorinated Fullerenes

Abstract

In situ x-ray diffraction experiments of the fluorinated fullerenes, C₆₀F _x (x = 0, 36 and 48) at high temperatures have been undertaken. The structural phase transformation of C₆₀F₄₈ was observed at about 358 K. It was also found that the lattice parameters of the low temperature phase of C₆₀F₄₈ show anomalous change at about 310 K. The thermal expansion coefficients of the fluorinated fullerenes were determined by using the change of the lattice parameters with temperature.     

Crystal structure of 1-chloroanthraquinone

The X-ray crystal structure of 1-chloroanthraquinone is determined. The compound C₁₄H₇O₂Cl, is monoclinic in P2₁(#4) with a = 7.763(1), b = 3.973(2), c = 16.947(1) Å, = 95.13(1)°, V = 520.6(3) ų, D _calc = 1.548 g/cm³, and Z = 2. In the molecular structure, the Cl atom is obviously repelled by O(1). The major force of crystal formation comes from aromatic ring stacking and C–H-aromatic interaction.     

17α-acetoxy-17β-methyl-16β-phenyl-D-homo-4,6-pregnadiene-3,17a-dione: synthesis and crystal structure determination of a new rearranged pregnane derivative

The title compound is C₂₉H₃₄O₄, tetragonal, P4₃, a = b = 10.310(1), c = 23.871(2)Å. The A, B, C, and D rings adopt envelope, half-chair, chair, and distorted chair conformations, respectively. The phenyl ring is planar. The methyl substituents at the A/B, C/D, and at C(17) are axial; and the –OCOCH₃ group at C(17) and phenyl ring at C(16) are equatorial. The molecules in the crystal are held together by van der Waals forces and several C–H···O hydrogen bond interactions.     

Crystal structure of 3,4-dimethoxybenzoic acid

The crystal structure of 3,4-dimethoxybenzoic acid (1) was obtained by single-crystal X-ray diffraction. Crystallization of 1 occurs in the centrosymmetric triclinic space group (No. 2) with a = 4.8727(5) Å, b = 8.4926(7) Å, c = 11.2333(14) Å; = 101.365(8)° = 102.010(8)° = 105.784(8)°; and Z = 2. Compound 1 forms hydrogen bonded dimers across an inversion center. Details of the structure and spectroscopic results are presented and discussed.     

Crystal structure of the quaternary alloy CuTaInSe3

The crystal structure of the quaternary compound CuTaInSe₃ belonging to the system (CuInSe₂)_1‐x(TaSe)_x with x= 0.5, was analyzed using X‐ray powder diffraction data. This material is isostructural with the CuFeInSe₃ compound, and crystallize in the tetragonal space group P42c (Nº 112), Z = 1, with unit cell parameters a = 5.7831(1) Å, c = 11.6227(4) Å, V = 388.71(2) ų. The Rietveld refinement of 18 instrumental and structural variables led to R_p = 8.0%, R_wp = 9.5%, R_exp = 6.3% and χ² = 1.5 for 4501 step intensities and 144 independent reflections. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal Structure of Europium C60 Compounds

Abstract

We have studied crystal structures of europium C₆₀ compounds by high resolution x-ray diffraction measurements. In the systematic synthesis of Eu _x C₆₀ for x (0 ≤ x ≤ 6), two stable phases appear at x = 3 and 6. Eu₆C₆₀ has a bcc structure, which is an isostructure to M ₆C₆₀ (M represents an alkali or alkaline earth metal). Eu₃C₆₀ has a superstructure derived by doubling the fcc pristine C₆₀ crystal along three principal axes. This superstructure comes from an ordering of cation vacancies, which is analogous to Yb_2.75C₆₀.     

Field Dependence of 1 and 2 Photon Charge Generation in Anthracene and Phenazine

Charge carrier generation through photexcitation with strongly absorbed light and very weakly absorbed light has been compared for anthracene and phenazine crystals. No attempt was made to prepare clean surfaces, but purified crystals were used. The field dependence for strongly absorbed light was similar for both crystals, superlinear at low fields, linear at high fields. For weakly absorbed light, the photo generation of charge in anthracene could be described as Onsager type behavior, generation in phenazine could not. These results are discussed in terms of the charge generation process.     

Synthesis, crystal structure and molecular modeling (AM1) of two 5-arylidene derivatives of Meldrum's acid

The synthesis and structural characterization of two 5-Arylidene derivatives of Meldrum's acid (2,2-dimethyl-1,3-dioxane-4,6-dione) are described: 5-(4-Nitrobenciliden)-2,2-dimethyl-1,3-dioxane-4,6-dione (3a), and 5-(4-Methoxybenciliden)-2,2-dimethyl-1,3-dioxane-4,6-dione (3b). The structure of 3a was refined to R₁ = 0.0421 for 2148 reflections (with I > 2 (I)). Crystal data for 3a: C₁₃H₁₁NO₆, orthorhombic, space group Pbca, a = 16.008(3), b = 6.137(1), c = 25.281(5) Å, V = 2483.6(8) ų, Z = 8. The structure of 3b was refined to R₁ = 0.0496 for 4681 reflections (with I > 2(I)). Crystal data for 3b: C₁₄H₁₄O₅, triclinic, space group P1, a = 9.131(2), b = 9.922(2), c = 14.490(3)Å, = 85.076(6), = 84.80(3), = 89.37(2)°,V = 1302.4(5) ų, Z = 4. The results of crystallographic and molecular modeling (AM1) were compared. The molecules in the crystal are held together, in both compounds, by van der Waals forces and C—H···O hydrogen bond interactions.     

Crystal and molecular structure of benzophenone azine: evidence for an Fe(II) carbene intermediate

Benzophenone azine crystallizes in the monoclinic space groupA2/a (No. 15) witha=16.303(3) Å,b=5.4864(2) Å,c=21.973(5) Å, =85.52(2)°,V=1959.4(8) ų, andD _calc=1.22 g cm^–3 forZ=4. The structure was solved by direct methods and refined againstF to a finalR value of 0.047. The unit cell contains four molecules of the title compound; the asymmetric unit consists of half a molecule. Despite the high crystallographic symmetry, the two halves of the molecule arenot related by a center of symmetry; instead, the molecule adopts C₂ symmetry; the molecular C₂ axis is coincident with the crystallographic twofold axis. The formation of benzophenone azine from the reaction of the iron-containing Lewis acid complex [(⁵-C₅H₅)Fe(CO)₂(THF)]⁺ [BF₄]^– and diphenyldiazomethane provides strong evidence for an Fe(II) carbene intermediate.     

Crystal and molecular structure of potassium 2-amino-6-sulfinato-purine monohydrate

The crystal and molecular structure of the title compound, K[C₅H₄N₅O₂S]H₂O, has been determined at room temperature. The structure determination reveals that the negative charge on the anion is localised on the sulfinate group which results in significant rearrangement of -electron density within the purine ring. The K⁺ cation exists in a N₃O₄ donor set which defines a distorted trigonal prismatic geometry. Crystals of K[C₅H₄N₅O₂S]H₂O are triclinic with space group and unit cell dimensionsa=8.248(2),b=8.710(2),c=6.988(6) Å, =99.87(4), =102.84(5), and =78.35(2)°,Z=2.     

Synthesis, crystal structure, and molecular modeling (AM1) of Methyl 6-chloro-4-(2-chlorophenyl)-5-formyl-2-methyl-1, 4-dihydropyridine-3-carboxylate

The synthesis and structural characterization of Methyl 6-chloro-4-(2-chlorophenyl)-5-formyl-2-methyl-1,4-dihydropyridine-3-carboxylate is described. The structure was refined to R₁ = 0.0470 for 2665 reflections (with I > 2(I)). Crystal data: C₁₅H₁₃C₁₂NO₃, monoclinic,space group P2₁/c, a = 11.163(9), b = 14.484(8), c = 9.422(7) Å, V = 1512.9(19) ų, Z = 4. The results of crystallographic and molecular modeling (AM1) were compared. The Cl atom attached to the phenyl group has two possible orientations, having 75% (sp) and 25% (ap) occupancy, respectively. The molecules in the crystal are held together by means of intermolecular hydrogen bonds of the type N=H...O and by C=H...O interactions.     

Crystal structure characterization of the quaternary compounds CuFeAlSe3 and CuFeGaSe3

The crystal structure of the chalcogenide compounds CuFeAlSe₃ and CuFeGaSe₃, belonging to the system I‐II‐III‐III₃, were characterized using X‐ray powder diffraction data. Both compounds crystallize in the tetragonal space group P42c (N° 112), Z = 1, with unit cell parameters a = 5.609(1) Å, c = 10.963(2) Å for CuFeAlSe₃ and a = 5.6165(3) Å, c = 11.075(1) Å for CuFeGaSe₃. These compounds are isostructural with CuFeInSe₃, and have a normal adamantane structure. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal and molecular structure of 3-chloro-3,6-dinitro-2,2-dimethyl-4-chromanone, C11H9N2O6Cl

3-Chloro-3,6-dinitro-2,2-dimethyl-4-chromanone is the first 3-chloro-3-nitro-4-chromanone to be synthesized by nitrating its corresponding 4-chromanone at the 3 position and then chlorinating the nitration product. Its structure was determined by IR, NMR, MS and x-ray crystallography. It crystallizes as a pair of enantiomers with 2 molecules in the primitive triclinic space group P (#2) with a = 9.476(2), b = 10.906(3), c = 6.578(5) Å, and = 101.08(3), = 90.13(3), = 73.23(1)°, V = 637.7500 ų, and Z = 2. The nitro group at the 6 position conjugates with the benzene ring. The pyranone ring has a half-chair conformation; the chloro group occupies the pseudoequatorial position, and the nitro group occupies the pseudoaxial position. The 2 and 3 positions are essentially antiperiplanar, minimizing steric interaction.     

Crystal structure and vibrational spectra of polyamine-copper(II) complexes

The structures of [Cu(en)(H₂O)₂]SO₄ (I), [Cu(en)₂](NO₃)₂ (II) and [Cu(trien)I]I (III) have been determined by single crystal X-ray diffraction. ComplexI is monoclinic, space group C2/c, with unit cell parametera=7.232(1),b=11.725(2),c=9.768(1), =105.50(1)°, andZ=4. ComplexII is also monoclinic, space group P2₁/a, witha=7.978(2),b=9.982(4),c=8.218(3), =111.11(2)°, andZ=2. ComplexIII is orthorhombic, space group P2₁2₁2₁, witha=8.098(1),b=11.902(1),c=13.682(2), andZ=4. The structures were solved by direct methods and refined by full-matrix least-squares to finalR values of 0.031, 0.043 and 0.036 for complexesI, II, andIII, respectively. ComplexesI andII show an octahedral coordination geometry. ComplexIII shows a square pyramidal coordination geometry. ComplexI forms infinite monodimensional chains where the SO ₄ ^2– ions acts as a bridge between two neighboringen molecules. The vibrational spectra of these complexes agree well with their crystal structures. Structure and stability of seven other related Cu(II) complexes of (trien), (dien)₂, (en)₂ and (en) are inferred in this study.     

Crystal structure and spectroscopy of 4-N-benzylaminocoumarin

The structure of 4-N-benzylaminocoumarin (C₁₆H₁₃NO₂) has been determined by X-ray diffraction and the Ft-ir,¹H- and¹³C-nmr spectra of the compound were recorded. Crystals of the compound are monoclinic, space group P2₁/c, with cell dimensiona=8.077(2),b=14.598(4),c=10.890(3) Å, and =97.76(3)°. The Ft-ir and nmr spectra indicate that the nitrogen atom is in the amino form in solution. The crystal structure is consistent with this observation, but the C(3)–C(4) double bond is clearly delocalized to include the lone pair on the nitrogen atom.     

Metastable States and CDW Conductivity in NbSe3

A study of the response of niobium triselenide to pulsed currents shows that the field-induced motion of the charge-density waves (CDWs) leaves them in long-lived metastable states in which, presumably, some distortion is stabilised by pinning. Evidence of this is provided by a reduction in Ohmic conductivity after current flows non-linearly through a specimen originally in thermal equilibrium, and by a transient increase in the non-linear conductivity on subsequent reversals of the current. A gradual increase in the non-linear conductivity during pulses applied repeatedly in the same sense is found to arise from a thermally-induced change in the strength of the pinning. The possible origin of this change is discussed.     

Crystal structure of pyrazole derivatives. IV. 5-chloro-4-chlorosulfonyl-3-methyl-1-phenylpyrazole

The title compound crystallizes in space groupP2 ₁/a witha=17.063(1),b=13.208(1),c=21.260(2) Å, =99.51(1)°,V=4726(1) ų,Z=16, there are four independent molecules in the asymmetric unit. The phenyl and pyrazole rings are planar, to within experimental accuracy, making different dihedral angles in the independent molecules: 42.2(1), 129.5(1), 52.5(1), and 46.2(1)°.     

Structure of (Z)-1-p-methoxyphenyltelluro-1,4-diphenyl but-1-en-3-yne

C₂₃H₁₈TeO,M _r=437.97, ,a=9.940(2),b=13.664(3),c=7.895(2) Å, =80.60(1), =69.71(2), =75.95(1)°,V=972.0(4) ų,Z=2,R=0.041 for 2668 observed reflections. The Te–C bond distances are 2.109(5)Å and the C–Te–C angle is 96.0(2)°. The phenyl rings are planar to within experimental accuracy, making dihedral angles of 64.6(2), 65.3(2) and 31.1(3)°.     

Self-Assembled Germanium-Dot Multilayers Embedded in Silicon

We report mainly on structural investigations on nanoscale Ge rich islands, the growth of which is driven by misfit strain (Stranski-Krastanow growth mode). Results of several methods, i.e. atomic force microscopy, transmission electron microscopy, and mainly x-ray diffraction and x-ray reflectivity measurements are presented and discussed.     

Application of Infrared ATR Spectroscopy to Liquid Crystals. III

Infrared absorption measurements of nematic N-(p-ethoxybenzylidene)-p'-cyanoaniline (EBCA) under a DC electric field were performed by means of our previously reported ATR method. DC voltages up to 15V were applied to the nematic liquid crystal 15 μm thick between a silicon ATR prism (probing electrode) and an In₂O₃-coated glass electrode (opposite electrode). By using this method the orientational behavior of molecules in boundary layers about 1 μm thick at the Si electrode was investigated.

The threshold voltage for the dielectric orientation varied from 2 to 6 V depending upon the boundary conditions at the opposite electrode, and the maximum degree of order of homeotropic orientation was found to be 0.6–0.7. A storage effect, in which a homeotropic texture induced by the electric field remains unaltered even if the field is removed or reversed, was observed.