Schiff bases and their complexes with metal ions. Part II. Structures of N-n-butyl-2-hydroxy-1-naphthaldimine and bis[N-n-pentyl-2-hydroxy-1-naphthaldiminato]nickel(II)

The Schiff base ligand (1), [C₁₅H₁₇NO] crystallizes in the monoclinic space group P2₁/c witha=10.054(3),b=10.313(3), c=13.173(4)Å, =107.42(4)°,V=1303.2(7)ų,Z=4,Dx=1.159 g cm^–3, and (MoK)=0.674 cm^–1. The C2-O[1.23(1)Å] and C3–C4 [1.33(2)Å] bond lengths are short, due to its quinoidal structure. In the Schiff base nickel complex (2), [Ni(C₁₆H₁₈NO)₂] the asymmetric unit is comprised of two half-complexes. It crystallizes in the triclinic space group witha=5.124(3),b=16.227(3),c=16.886(4)Å, =95.47(8), =96.00(1), =90.71(4)°,V=1389.6(9) ų,Z=2,Dx=1.289 g cm^–3, and (MoK) =12.1 cm^–1. The coordination of the Ni(II) ions are square planar with bond angles between 87.9(1) and 92.1(1)°. The Ni–O and Ni–N distances are 1.819(2), 1.922(2) and 1.823(2), 1.914(3)Å in these two complexes.     

Complexation with diol host compounds. Part 3. Molecular inclusion of 4-methylcyclohexanone and 2-methylcyclohexanone by the host,trans-9,10-dihydroxy-9,10-diphenyl-9,10-dihydroanthracene

The structures of the 12 molecular complexes oftrans-9,10-dihydroxy-9,10-diphenyl-9,10-dihydroanthracene with 4-methylcyclohexanone (1) and with 2-methylcyclohexanone (2) have been determined by X-ray crystallography. The crystal data are as follows: Compound (1):P2₂/c,a=8.838(2) Å,b=8.92(1) Å,c=20.879(8)=Å,=98.67(2)°,V=1627(2) ų,Z=2 andR=0.062 for 2201 unique MoK reflections; Compound (2):P¯1,a=8.917(3) Å,b=9.900(2) Å,c=11.250(4) Å,a=68.72(2)°,=64.39(3)°, =74.86(2)°,V=828.1(5) ų,Z=1 andR=0.098 for 2563 unique reflections. Both inclusion compounds exhibit O-HO=C hydrogen bonding interactions. The thermal properties of these compounds have been characterized by DTA and TGA thermograms.     

Conformations of barbiturates related to pentobarbitone. I. Crystal structure oftrans-5-ethyl-5-but-1′-enyl barbituric acid

trans-5-Ethyl-5-but-1-enyl barbituric acid, mp 112° C, is triclinic, space groupP¯1 witha = 8.228(1),b = 10.445 (2),c = 7.265(1) Å, = 111.165(1), = 105.512(1), = 95.079(1)°, and Z = 2. The crystal structure was determined by direct methods and refined to R = 0.047 by full-matrix least-squares procedures for 2308 observed diffraction maxima. The molecules form ribbonlike structures alongb, held together by N-H ... O=C hydrogen bonds and van der Waals forces between an alternating sequence of ethyl and but-1-enyl groups.     

A new class of flexible energetic salts. Part 7: The structures of the guanidinium and hydroxyguanidinium salts of dinitramide

The crystal structures of two amine base salts of dinitramide, the guanidinium 1, and the hydroxyguanidinium 2, have been determined. 1 crystallizes in the triclinic space group with cell dimensions a = 8.325(2) Å, b = 9.301 (2) Å, c = 9.868(2) Å, = 84.73(3)°, = 69.25(3)°, = 67.55(3)°, while 2 crystallizes in the noncentric monoclinic space group Pc with cell dimensions a = 7.098 (2) Å, b = 3.5160 (10) Å, c = 14.358(3) Å, = 98.940(10)°. The structures of 1 and 2 contain protonated amine cations and dinitramide anions linked by hydrogen bonding. In both structures the conformations adopted by the dinitramine anions can be related to the types of hydrogen bonds it forms with the surrounding amine cations.     

The crystal and molecular structures of formyl-, cyano-, and amino-cyclopentadienyldicarbonylnitrosylchromium

The x-ray crystallographic structures of ( ⁵-C₅H₄CHO)Cr(CO)₂NO (I), ( ⁵-C₅H₄CN)Cr(CO)₂NO (II), and ( ⁵-C₅H₄NH₂)Cr(CO)₂NO (III) are described. The formyl and amino derivatives were obtained from a literature preparation (Macomber and Rausch, 1983). The cyano derivative (II) was obtained by conversion of ( ⁵-C₅H₄COOH)Cr(CO)₂NO into [( ⁵-C₅H₄C(O)NH₂]Cr(CO)₂NO, followed by dehydration of the amide in acetic anhydride. (I) crystallizes in the monoclinic space groupP2₁/n witha=8.028(3),b=11.605(4),c=9.730(3)Å,=90.04(2)°, andD _calc=1.69 g cm^–3 forZ=4. Refinement led to anR value of 0.031 based on 1279 observed reflections ([I>-3(I)]). (II) belongs to the triclinicP¯1 witha=6.838(3),b=6.879(3),c=10.130(3)Å,=92.23(2),=92.98(2), =107.65(3)°, andD _calc=1.67 g cm^–3 forZ=2. Refinement gaveR=0.042 for 1543 observed reflections. (III) was found to be orthorhombicPbca witha=7.259(3),b=13.449(3),c=18.090(5)Å, andD _calc=1.64 g cmsu–3 forZ=8. Refinement producedR=0.026 for 767 observed reflections. In (I) the electron-withdrawing formyl group is foundtrans to the nitrosyl. The same holds for the cyano group in (II), but the amino function in (III) is nottrans to any of the tripod ligands.     

Crystal structure of 1,2,4,6-tetraphenylpyridinium tetrabromoferrate(III)

The title structure, which belongs to the triclinicP¯1 space group witha=13.901(4),b=10.732(1),c=10.570(8)Å=109.14(4),=96.17(4), =90.34(2)°, is refined toR=0.052 for 2985I3(I) reflections. The structure consists of a non-interacting 1,2,4,6-tetraphenylpyridinium and tetrahedral tetrabromoferrate (III) ions.     

Crystal growth and characterization of the CdGaCrSe(4‐X)S(X) system

Single‐crystal of the CdGaCrSe_(4‐X)S_(X) system (x = 0; 1; 2; 3; 4) were grown by the chemical vapour‐phase transport technique. The crystals were obtaine by using CdCl₂ as transporting agent for the composition with x = 1, and CrCl₃ for those with x = 0; 2; 3 and 4. X‐ray powder diffraction analysis indicated that some of the samples crystallizes in the tetragonal system with space group I‐4 (CdGaCrSe₃S , x = 1; CdGaCrSe₂S₂ , x = 2), or in a cubic system with space group Fd‐3m (CdGaCrSeS₃, x = 3; CdGaCrS₄, x = 4), however the sample of CdGaCrSe₄ (x = 0) crystallizes in rhombohedral system. Magnetic measurements show significant changes in the magnetic interactions behaviour probably due to the anionic substitutions. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Studies of systemic acylanilide fungicides. Part I. Crystal structure and molecular conformation ofdl-methyl-N-(2,6-dimethylphenyl)-N-(2-methoxyacetyl) alaninate

The crystal structure of metalaxyl (C₁₅H₂₁NO₄) was determined by three-dimensional X-ray analysis from diffractometer data. The crystals are monoclinic,P2₁/c,a=7.851(3) Å,b=13.119(10) Å,c=15.107(7) Å,=101.71(6)°,Z=4,D _x=1.218 g cm^–3, (MoKa)=0.095 mm^–1. FinalR=0.079 for 1203 observed reflections. The dimethylphenyl ring is almost perpendicular to the amidic plane of the molecule.     

Crystal and molecular structure of: 5-(1-oxoethyl)-1-methyl-2-(5-bromo-6-methoxy-2-naphthyl)-6-oxabicyclo[3.2.1]octan-7-one and 5-(1-oxoethyl)-1-methyl-2-(5-bromo-6-methoxy-2-naphthyl)-6-oxabicyclo[3.2.1]octane

X-ray crystallographic studies of the two title compounds have shown that the molecules crystallize in the same triclinic space group, , with very similar cell dimensions. For C₂₁H₂₁BrO₄,a=12.056(5),b=13.206(5),c=7.595(3)Å, =90.38(3), =106.07(3) and =124.42(3)° and for C₂₁H₂₃BrO₃,a=12.076(6),b=13.090(5),c=7.490(3)Å, =92.65(5), =104.90(5) and =124.55(5)°. Both compounds possess the oxabicyclo[3.2.1]octane bridged ring system and differ only at the carbon to the ring oxygen where the Csp³ in the ether is replaced by Csp²=O in the lactone. Both cyclohexane rings adopt distorted chair conformations and the lactone and ether rings approximate closely to the envelope conformation. The bromine substituent at C(4) results in distortion of the naphthalene ring. Both molecules pack with the naphthalene rings parallel to each other with interplanar spacings of 3.71 Å in the ether and 3.66Å in the lactone.     

Reaction between [Ru3(CO)10(μ-dppm)] (dppm = Ph2PCH2PPh2) and Te2(C6H4OEt-4)2: X-ray crystal structure of [Ru2(CO)6{μ-C6H4PPh(CH2)PPh}]

Treatment of [Ru₃(CO)₁₀(-dppm)] (1) with the ditelluride Te₂(C₆H₄OEt-4)₂ in refluxing toluene afforded the new aryltellurol bridged complex [Ru₂(CO)₄(-TeC₆H₄OEt-4)₂ (-dppm)] (2) together with three known complexes [Ru₄(CO)₈(-CO)(₄-Te)₂(-dppm)] (3), [Ru₂(CO)₆{-CH₂PPh(C₆H₄)PPh}] (4), and [Ru₂(CO)₆{-C₆H₄PPh(CH₂)PPh}] (5). All the four complexes were characterized by spectroscopic methods, including an X-ray structure determination for 5. Complex 5 crystallizes in the monoclinic space group P2₁/c with a = 13.650(2), b = 9.995(2), c = 18.929(3) Å, = 97.49(2)°, V = 2560.4(8) ų, and Z = 4. In this complex the two ruthenium atoms are bridged by the phosphino-phosphide ligand C₆H₄PPh(CH₂)PPh which is attached to one Ru by the C₆H₄ group and a P atom while to the other Ru by both the two P atoms. Both the ruthenium atoms show distorted octahedral geometry. The Ru—Ru bond length is 2.8719(7) Å.     

Crystal growth of the CdGa2(1‐x)Cr2xSe4 compounds by chemical transport method

Single crystals of CdGa_2(1‐x)Cr_2xSe₄ compounds for 0 ≤ x ≤ 1 have been grown by using the chemical vapor transport technique in a closed system. The transporting agent was CdCl₂ in a proportion of 0.75 mg/cc of capsule. The starting material was previously synthetized. The structural characterization on the crystals were done by powder x‐ray diffraction studies. The results show three different phases for various Cr concentration ranges: spinel structure for x ≥ 0.7, rombohedral for 0.6 ≥ x ≥ 0.5 and tetragonal for 0.4 ≥ x ≥ 0. That is, the chromium dilution in the CdCr₂Se₄ compound by Ga atoms produces very significant changes in the structural atomic arrangement. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal structures of the new diphosphates,K2NiP2O7 and K6Sr2Ni5(P2O7)5

Crystalline K₂NiP₂O₇ (I): monoclinic, P2₁,a=9.230(2),b=17.540(8),c=8.319(9)Å, =91.44(2)°,Z=8,d _calc=3.067 g cm^–3, MoK =0.71069Å,R/R _w=6.5/9.4%, is characterized by the existence of face sharing NiO₆ octahedra with Ni–Ni separation of 2.827 Å (Ni–O; 1.93(2)–2.17(2)Å). K⁺ is seen in sites of seven, six, and fivefold coordination (K–O, averages; 2.83(2), 2.81(2), and 2.77(2)Å, respectively) P₂O₇ ^4– groups are observed in semieclipsed conformation. K₆Sr₂Ni₅(P₂O₇)₅ (II) crystallizes in monoclinic space group P2₁/c;a=11.038(7),b=9.533(13),c=7.438(2)Å, =100.13(4)°,D _calc=3.309 g cm^–3,Z=2,R/R _w=6.4/8.1%. Nickel atoms are distributed on planes parallel to the crystallographic (100) plane at =0 and =0.5. On the planes, =0, Ni²⁺ ions form successive linked trimers of edge sharing NiO₆ octahedra (Ni–Ni, 3.018(1), 3.008(1)Å; Ni–O, av 2.07(2)Å). The intermediate planes (=0.5) contain isolated and six coordinate Ni²⁺ ions (Ni–O av. 2.09(2)Å). Seven-coordinate potassium ions (K–O, av. 2.74(2)Å) are located on intermediate planes at =0.25 and 0.75. P₂O₇ ^4– groups are found in eclipsed conformation. Strontium atoms are located between nickel and potassium planes and are surrounded by seven oxygen atoms (Sr–O, av. 2.586(2)Å).     

Microwave dielectric properties of (1‐x)La(Mg0.5Sn0.5)O3‐x(Sr0.8Ca0.2)3Ti2O7 ceramic system with a near zero temperature coefficient of resonant frequency

In this study, the microwave dielectric properties of (1‐x)La(Mg_0.5Sn_0.5)O₃‐x(Sr_0.8Ca_0.2)₃Ti₂O₇ ceramic system prepared by the conventional solid‐state method have been investigated for application in mobile communication. It was found that the diffraction peaks of (1‐x)La(Mg_0.5Sn_0.5)O₃‐x(Sr_0.8Ca_0.2)₃Ti₂O₇ ceramic system shift to higher angles as x increases from 0.2 to 0.4. It was also found that the X‐ray diffraction patterns of the 0.8La(Mg_0.5Sn_0.5)O₃‐0.2(Sr_0.8Ca_0.2)₃Ti₂O₇ ceramics exhibited no significant phase difference at different sintering temperatures. The average grain size of the (1‐x)La(Mg_0.5Sn_0.5)O₃‐x(Sr_0.8Ca_0.2)₃Ti₂O₇ ceramic system decreased from 6.4 to 4.3 μm as the value of x increased from 0.2 to 0.4 sintered at 1550 °C for 4 h. The dielectric constant increased from 26.6 to 35.9 and the quality factor (Q×f) decreased from 31,600 to 23,300 GHz for (1‐x)La(Mg_0.5Sn_0.5)O₃‐x(Sr_0.8Ca_0.2)₃Ti₂O₇ ceramic system as the x value increases from 0.2 to 0.4 sintered at 1550 °C for 4 h. The average value of temperature coefficient of resonant frequency (τ_f) increased from ‐18 to +8 ppm/ K as the x value increases from 0.2 to 0.4. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structures of three isomeric ring-brominated PEA β-blockers: [C13H21BrNO3]+·Cl−, [C13H21BrNO3]+·[CH3SO3]−, and [C13H21BrNO3]+·[C2HO4]−

The X-ray crystal structures of three-blockers of the phenylethanolamine (PEA) class have been determined by single crystal techniques. They are (I): (±)-2-(2-bromo-3,4-dimethoxyphenyl)-2-hydroxy-N-isopropylethylamine hydrochloride; (II): (±)-2-(3-bromo-4,5-dimethoxyphenyl)-2-hydroxy-N-isopropylethylamine methylsulphonate; (III): (±)-2-(2-bromo-4,5-dimethoxyphenyl)-2-hydroxy-N-isopropylethylamine hydrogen oxalate. A conformational energy map of a partially hydrated model cation as a function of the principal torsion angles ₁ and ₂ shows the transperpendicular conformer (₁90°, ₂180°) to be the most stable. This conformation is adopted by cations of (II) and (III) in their crystals, but for (I), ₁=52.3(6)° is observed. Non-bonded pharmacophoric distances lie within the expected ranges.     

Electrical and magnetotransport properties of La0.7Sr0.3MnO3/TiO2 composites

The composite samples with nominal compositions of (1‐x) La_0.7Sr_0.3MnO₃ + x TiO₂ (x = 0, 0.05, 0.10, 0.15 and 0.20) were synthesized via solid state reaction process. The X‐ray diffraction and scanning electronic microscopy observations reveal no reaction between La_0.7Sr_0.3MnO₃ (LSMO) and TiO₂ phases. Temperature dependence resistivity measurements show that TiO₂ phase shifts the metal‐insulator transition temperature (T_p) towards lower temperature and increases the resistivity. Moreover, the magnetization of the composite samples decreases with TiO₂ content. An enhancement in magnetoresistance is observed in the composite samples with x = 0.05 and x = 0.10 at low magnetic fields, which is encouraging for potential application of magnetoresistive materials at low field. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The crystal structure of a cyclodecabis[1,2,3]selenadiazole

4,5,6,10,11,12-hexahydrocyclodeca[1,2-d6,7-d]bis[1,2,3]selenadiazole, C₁₀H₁₂N₄Se₂, crystallizes in triclinic space group P witha=5.4625(3),b=7.2091(4),c=8.3122(6) , =65.313(5), =77.476(5), =77.442(5)°,V=287.35(4) ³,Z=1. The structure was refined toR=0.031 andR _w=0.030 for 2018 observed reflections. The molecule lies on an inversion center. The cyclodecadiene ring adopts an elongated chair conformation. The near-zero torsion angle of the elongated chair lies at the ring-fusion bonds, with a magnitude of 2.9(3)°. The five atoms of the selenadiazole ring exhibit maximum deviation 0.005(2) from planarity, with the adjacent carbon atoms lying respectively 0.020(2) and 0.059(2) to the same side of this plane. The torsion angles about the bonds comprising the sides of the elongated chair vary in magnitude from 61.0(2)° to 55.7(2)°. The cyclodecadiene C=C bond lengths are 1.368(2) . The selenium-carbon bond length is 1.850(2) . The Se–N distance is quite long, 1.888(2) .     

RHEED studies of the growth of Si(001) by gas source MBE from disilane

The growth of Si(001) from a gas source molecular beam epitaxy system (Si-GSMBE) using disilane (Si₂H₆) was investigated using reflection high-energy electron diffraction (RHEED). The surface reconstructions occurring between 100 and 775°C were studied as a function of both substrate temperature and surface coverage. We report the first observation of (2x2) and c(4x4) reconstructions during growth at substrate temperatures near 645°C using Si₂H₆. All growth was found to be initiated by the formation of three-dimensional (3D) islands which coalesced at substrate temperatures above 600°C. The surface reconstruction was found to change from a disordered to an ordered (2x1)+(1x2) structure at 775°C via intermediate (2x2) and c(4x4) phases. Thereafter, growth was found to proceed in a 2D layer-by-layer fashion, as evidenced by the observation of RHEED intensity oscillations. This technique has been used, for the first time, to calibrate growth rates during Si-GSMBE. The intensity oscillations were measured as a function of both substrate temperature and incident beam flux. Strong and damped oscillations were observed between 610 and 680°C, in the two-dimensional growth regime. At higher temperatures, growth by step propagation dominated while at lower temperatures, growth became increasingly three-dimensional and consequently oscillations were weak or absent. Similarly, there was a minimum flux limit ( <0.16 SCCM), below which no oscillations were recorded.     

Diammonium μ-oxobis[trichloroferrate(III)] salts. Crystal and molecular structure of bis(benzyldimethylphenylammonium) μ-oxobis(trichloroferrate)

Several alkyl-, aralkyl-, and aryl-substituted diammonium-oxobis[trichloroferrate(III)] salts, of potential interest as model compounds for the study of certain electrophysical and biological processes, are synthesized via the corresponding tetrachloroferrate(III) salts and are characterized by IR and Raman spectroscopy. A structure analysis is performed on the representative bis(benzyldimethylphenylammonium)-oxobis(trichloroferrate). The (tetracoordinate) iron atoms in the oxo-bridged dinuclear anion of the salt each possess an ever so slightly distorted tetrahedral ligand environment; the bridge geometry [Fe-O distances 1.757(5) and 1.775(5) Å, Fe-O-Fe angle 147.7(3)°] compares well with that of other salts containing the [Cl₃Fe-O-FeCl₃]^2- anion. Crystallographic Data:a=26.392(5) Å,b=14.015(3) Å,c=9.638(2) Å,=92.65(2)°, andZ=4; space groupP2₁/n.R(F)=0.070,R _W (F)=0.078 for 4447 observed reflections.     

Growth and characterization of superconductive Nd2‐xCexCuO4‐y single crystals

Nd_2‐xCe_xCuO_4‐y single crystals with different x values have been successfully grown by Traveling Solvent Floating Zone method (TSFZ). Electronic properties of Nd_2‐xCe_xCuO_4‐y single crystals with various x have been studied in detail. The results show that superconductivity can be found in crystals with x > 0.1 (0.13‐0.18) directly grown at oxygen‐reduced atmosphere without post‐annealed, while no superconductivity appears in crystals with x < 0.1 at the same atmosphere. It is also found that, the segregation coefficient of Ce is determined to be 0.946 and transition temperature Tc (onset) reaches maximum value of 23.5 K at nominal composition x = 0.165. With further increase of Ce concentration, transition temperature of single crystals declines due to the precipitation of secondary Phases. In addition, the variation of lattice constants of Nd_2‐xCe_xCuO_4‐y single crystals with different x is also given. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)