Crystal Structure of 1,3-Alternate 25,26,27,28-Tetra(tert-butoxyethoxy)calix[4]arene: a Selective Ag+ Extractant

Alkylation of calix[4]arene by 2-tert-butoxyethyl bromide led to the tetraalkylatedcalix[4]arene in the 1,3-alternate, the conformation of which has been established byX-ray crystallography. This spatial structure included a cavity potentially useful forhost–guest complexes achieved with metal cations, especially with Ag⁺. The titlecompound crystallizes in the monoclinic space group Cc with cell constants a = 29.901(2),b = 8.139(1), c = 22.264(3) Å, = 90°, = 117.08(1)°and = 90°. This conformer represents an example for Ag⁺-tunnelingacross an aromatic cavity. This behaviour could lead to important implications with regardto the metal cation- interaction expected for metal transport through ion channels,metal inclusion in fullerenes, intercalation of metal cations into graphites, etc.     

Synthesis and X-ray structural analysis of a unique Co-crystallization complex of [NaSal]2DB24C8 and [KSal]2DB24C8

Sodium salicylate (NaSal where Sal=2-hydroxybenzoate), when mixed with dibenzo-24-crown-8 (DB24C8) yields a bimetallic complex [NaSal]₂DB24C8 in most polar organic media, while potassium salicylate (KSal) under similar conditions shows a tendency to yield 11 or 21 complexes depending upon medium or synthesis. However, the presence of both NaSal and KSal together results in a unique mixed cation complex of composition NaKSal₂DB24C8. This product melts sharply (190-92°C) without decomposition, displays IR spectral characteristics comparable to those of [Na(Sal)]₂DB24C8, and is stable in aqueous media as shown by the detectable cation effect on the UV absorption bands of Sal and DB24C8. Single crystal X-ray analysis of NaK(Sal)₂DB24C8 reveals that the system represents a co-crystallization complex of individual (KSal)₂DB24C8 and (NaSal)₂DB24C8 molecules. The crystals are monoclinic,P2₁/c,a=19.976(2) Å,b=9.031(1) Å,c=25.541(5) Å,=122.065(9)°, ų,T=298 K,Z=2+2, CuK =1.5418 Å, and 2 (2.5°–100°). FinalR factor for the 3012 observed reflections (F>3) is 0.092. Both the Na₂- and K₂-molecules possess crystallographic centers of symmetry with one metal and its associated anion on each side of the crown ring. However, the conformations of the crowns are very different in the two molecules, with the K₂-crown being nearly planar and the Na₂-crown being quite puckered. Four oxygen atoms from the DB24C8 (KO, 2.680–2.908 Å) and three carboxyl oxygen atoms (KO, 2.472–2.708 Å) from separate salicylate ions coordinate with each potassium. Three oxygens from the crown (NaO, 2.536–2.65 Å) and three carboxyl oxygens (NaO, 2.31–2.563 Å) coordinate with each sodium. The salicylate ions lie on opposite sides and nearly perpendicular (77.2°, Na₂-molecule; 82.7° K₂-molecule) to each crown but coordinate to both of the metal ions within a molecule. The K⁺K⁺ and Na⁺Na⁺ distances in the respective molecules are 3.95 and 3.34 Å. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82044 (18 pages).     

Diaqua[N,N-di(2-carboxyethyl)-o-anisidinato]copper(II) Dihydrate [Cu(o-Andp)(H2O)2] · 2H2O: Synthesis and Crystal Structure

Crystals of [Cu(o-Andp)(H₂O)₂] · 2H₂O (where o-Andp^2–is -anisidine-N,N-di-3-propionate) were synthesized and studied using X-ray diffraction analysis. The crystals are triclinic: a= 12.063(1) Å, b= 12.483(3) Å, c= 13.586(2) Å, = 91.29(1)°, = 111.67(1)°, = 104.00(1)°, V= 1830.5(5) ų, space group P , Z= 2, and R= 0.0528 for 5965 reflections with I2(I). The two crystallographically independent complexes are isostructural. The tetragonal–bipyramidal coordination of copper(III) involves three O atoms, the N atom of the tetradentate ligand o-Andp^2–, and two O atoms from water. The aminodipropionate group of the ligand (average Cu–O 1.939 Å and Cu–N 2.051 Å) and one of the coordinated water molecules (Cu–O(w) 1.991 Å) lie in the equatorial plane. The second water molecule (Cu–O(w) 2.32 Å) and the methoxy O atom of o-Andp^2–(Cu–O 2.37 Å) are in the apical positions of the bipyramid.     

Synthesis and Structures of the Novel Pyridoxal Oxime Derivatives

Novel pyridoxal oxime derivatives were prepared and characterized by means of IR, ¹H and ¹³C NMR spectroscopy. The crystal structures of the 3-hydroxy-4-hydroxyiminomethyl-5-hydroxymethyl-1,2-dimethylpyridinium iodide 1 and 3-hydroxy-4-hydroxyiminomethyl-5-hydroxymethyl-1,2-dimethylpyridinium chloride monohydrate 2 were determined by X-ray analysis. The both compounds crystallize in the triclinic crystal system, space group P . Crystal data: 1 a = 6.286(2) Å, b = 8.748(4) Å, c = 11.736(4) Å, = 104.02(3)°, = 94.70(3)°, = 107.44(6)°, V = 589.0(4) ų, Z = 2, R = 0.0526; 2 a = 6.8980(5) Å, b = 8.6409(6) Å, c = 11.1777(6) Å, = 111.138(5)°, = 93.114(6)°, = 105.158(5)°, V = 591.57(7) ų, Z = 2, R = 0.0492. The bond distances and angles in both structures agree very well. The main difference between these structures was observed in the orientation of the hydroxymethyl group with respect to the pyridinium ring. In the both structures intramolecular hydrogen bond forming six-membered ring were observed. The intermolecular OsI hydrogen bonds in the crystal structure of the compound 1 form dimers. In the crystal structure of compound 2, the water molecules and chlorines build eight-membered rings, which are also connected to pyridinium cations by OsCl and OsO intermolecular hydrogen bonds forming a three-dimensional network.     

On the role of ion bombardment parameters in AES sputter depth profiling of Ta2O5/Ta with Ar+ and Xe+

Summary In order to study the influence of the ion bombardment parameters on the achievable depth resolution of AES sputter depth profiles, 500 Å thick Ta₂O₅-layers produced by anodic oxidation of polished polycrystalline Ta-substrates were sputter depth profiled with Ar⁺- and Xe⁺-ions in a Scanning Auger Microprobe. The 90%–10% interface widthsz were measured for bombarding ion energies from 0.5 to 5 keV and angles of incidence of 15°, 33° and 56°, respectively.z reduces from 48 Å for Ar⁺-bombardment at = 15° andE = 5 keV to 20 Å when bombarding at = 56° andE = 1 keV. The corresponding values for Xe⁺-bombardment are 31 Å and 18 Å. The influence of the ion bombarding energy and angle on the interface broadening is discussed by means of a simple model. From corresponding evaluations the maximum transportation length of layer species into the substrate is found to be proportional toE ^0.5.

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Zum Einfluß der Ionenbeschußparameter auf die Tiefenauflösung bei der AES-Sputtertiefenprofil-analyse von Ta₂O₅/Ta mit Ar⁺ und Xe⁺

     

On the crystal chemistry of three copper(II)-arsenates: Cu3(AsO4)2-III,Na4Cu(AsO4)2, and KCu4(AsO4)3

The three copper(II)-arsenates were synthesized under hydrothermal conditions; their crystal structures were determined by single-crystal X-ray diffraction methods:Cu₃(AsO₄)₂-III:a=5.046(2) Å,b=5.417(2) Å,c=6.354(2) Å, =70.61(2)°, =86.52(2)°, =68.43(2)°,Z=1, space group ,R=0.035 for 1674 reflections with sin / 0.90 Å^–1.Na₄Cu(AsO₄)₂:a=4.882(2) Å,b=5.870(2) Å,c=6.958(3) Å, =98.51(2)°, =90.76(2)°, =105.97(2)°,Z=1, space group ,R=0.028 for 2157 reflections with sin / 0.90 Å^–1.KCu₄(AsO₄)₃:a=12.234(5) Å,b=12.438(5) Å,c=7.307(3) Å, =118.17(2)°,Z=4, space group C2/c,R=0.029 for 1896 reflections with sin / 0.80 Å^–1.Within these three compounds the Cu atoms are square planar [4], tetragonal pyramidal [4+1], and tetragonal bipyramidal [4+2] coordinated by O atoms; an exception is the Cu(2)^[4+1] atom in Cu₃(AsO₄)₂-III: the coordination polyhedron is a representative for the transition from a tetragonal pyramid towards a trigonal bipyramid. In KCu₄(AsO₄)₃ the Cu(1)^[4]O₄ square and the As(1)O₄ tetrahedron share a common O—O edge of 2.428(5) Å, resulting in distortions of both the CuO₄ square and the AsO₄ tetrahedron. The two Na atoms in Na₄Cu(AsO₄)₂ are [6] coordinated, the K atom in KCu₄(AsO₄)₃ is [8] coordinated by O atoms.Die drei Kupfer(II)-Arsenate wurden unter Hydrothermalbedingungen gezüchtet und ihre Kristallstrukturen mittels Einkristall-Röntgenbeugungsmethoden ermittelt:Cu₃(AsO₄)₂-III:a = 5.046(2) Å,b = 5.417(2) Å,c = 6.354(2) Å, = 70.61 (2)°, = 86.52(2)°, = 68.43(2)°,Z = 1, Raumgruppe ,R = 0.035 für 1674 Reflexe mit sin / 0.90 Å^–1.Na₄Cu(AsO₄)₂:a = 4.882(2) Å,b = 5.870(2) Å,c = 6.958(3) Å, = 98.51(2)°, = 90.76(2)°, = 105.97(2)°,Z = 1, Raumgruppe ,R = 0.028 für 2157 Reflexe mit sin / 0.90 Å^–1.KCu₄(AsO₄)₃:a = 12.234(5) Å,b = 12.438(5) Å,c = 7.307(3) Å, = 118.17(2)°,Z = 4, Raumgruppe C2/c,R = 0.029 für 1896 Reflexe mit sin / 0.80 Å^–1.Die Cu-Atome in diesen drei Verbindungen sind durch O-Atome quadratisch planar [4], tetragonal pyramidal [4 + 1] und tetragonal dipyramidal [4 + 2]-koordiniert; eine Ausnahme ist das Cu(2)^{[4 + 1]}-Atom in Cu₃(AsO₄)₂-III: Das Koordinationspolyeder stellt einen Vertreter des Übergangs von einer tetragonalen Pyramide zu einer trigonalen Dipyramide dar. In KCu₄(AsO₄)₃ haben das Cu(1)^[4]O₄-Quadrat und das As(1)O₄-Tetraeder eine gemeinsame O—O-Kante von 2.428(5) Å, was eine Verzerrung der beiden Koordinationsfiguren CuO₄-Quadrat und AsO₄-Tetraeder bedingt. Die zwei Na-Atome in Na₄Cu(AsO₄)₃ sind durch O-Atome [6]-koordiniert, das K-Atom in KCu₄(AsO₄)₃ ist [8]-koordiniert.

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Zur Kristallchemie dreier Kupfer (II)-Arsenate: Cu₃(AsO₄)₂-III, Na₄Cu(AsO₄)₂ und KCu₄(AsO₄)₃

     

Bis[(1,2-bis(2-(o-hydroxyphenoxy)ethyloxy)ethane)-(isothiocyanato)potassium] [K2(NCS)2(C18H22O6)2]: Crystal and Molecular Structure

Complex of podand 1,2-bis(2-(o-hydroxyphenoxy)ethyloxy)ethane (L) with potassium thiocyanate, [K₂(NCS)₂L₂] (I) was synthesized and studied using X-ray diffraction analysis: space group P , a = 7.771 Å, b = 11.711 Å, c = 11.965 Å, = 72.22°, = 79.21°, = 89.07°, Z = 1. Structure I was solved by direct method and anisotropically refined by the full-matrix least-squares method to R = 0.040 for all 4370 independent reflections (CAD4 autodiffractometer, MoK ). Structure I contains [K(NCS)L] monomers of the host–guest type united into centrosymmetrical [K₂(NCS)₂L₂] dimers via two bridging OH groups (one group from two L podands). In the monomer, the L podand appears as though to envelope the octacoordinated K⁺ cation, whose the coordination polyhedron is a strongly distorted hexagonal bipyramid with all six oxygen atoms of the L podand in its base and the N atom of the SCN^– ligand and the O atom of one of OH group of the neighboring (in dimer) L podand at its axial vertices. Molecules of I in crystal are joined through the O–H···N hydrogen bonds to form broad infinite chains along the x-axis.     

Copper(I) Acetylenide π-Complexes. Synthesis and Structure of Cluster Compound HAmp[Cu9Cl8(C≡CCH2OH)2] (HAmp is 4-Aminopyridinium Cation)

Crystals of the HAmp[Cu₉Cl₈(CCCH₂OH)₂] cluster compound (HAmp is the 4-aminopyridinium cation (NH₂–C₅H₄NH)⁺) were obtained through ac electrochemical synthesis and their structure was determined using X-ray diffraction analysis (DARCh autodiffractometer, /2 scan mode, 3435 independent reflections with F 4(F), R = 0.047). The crystals are triclinic: space group P , a = 12.547(5) Å, b = 12.502(4) Å, c = 8.201(2) Å, = 75.93(2)°, = 82.21(3)°, = 76.05(3)°, V = 1207(2) ų, Z = 2. Two crystallographically independent moieties ^–(CCCH₂OH) were detected in the complex structure. Each moiety acts as a double bridging ,-ligand and binds four or five Cu(I) atoms, thus forming the [Cu₄(CCCH₂OH)] and [Cu₈(CCCH₂OH)₂] clusters. The shortest Cu···Cu distance is equal to 2.337(4) Å.     

Molecular encapsulation of transition metal complexes in cyclodextrins. Part 2. Synthesis and crystal structures of 2:1 adducts between α-cyclodextrin and metallocenium hexafluorophosphates [η5-C5H5)2M]PF6(M = Fe,Co, Rh)

The title metallocenium salts form crystalline 2:1 host:guest inclusion compounds with-cyclodextrin, [(⁵-C₅H₅)₂M]PF₆ · 2-CD · 8H₂O (1, M = Fe;2, M = Co;3, M = Rh). The X-ray crystal structures of1 and3, and the lattice constants, crystal system and space group of2 have been determined. Crystal data: triclinic, space groupP1 (No. 1),Z = 1;1,a = 13.865 (2) Å,b = 13.839 (2) Å,c = 15.520 (2) Å, = 91.43 (2)°, = 85.81 (2)°, = 120.22 (2)°, andR _F = 0.089 for 4257 observed MoK reflections [I > 3(I)];2,a = 13.810 (2) Å,b = 13.872 (2) Å,c = 15.560 (2) Å, = 93.99 (2)°, = 87.06 (2)°, = 120.04 (2)°;3,a = 13.756 (1) Å,b = 13.863 (1) Å,c = 15.561 (2) Å, =94.39 (1)°, = 86.92 (1)°, = 119.89 (1)°, andR _F = 0.061 for 11142 observed MoK reflections [I > 3(I)]. In the crystals of1 and3, two -cyclodextrin molecules are arranged head-to-head to form a dimer by means of intermolecular hydrogen bonding across the secondary hydroxyl faces of adjacent -CD monomers. The dimers are stacked along the crystallographicc axis to form a channel-type structure. The metallocenium cation is encapsulated within the cavity of the dimer, while the PF ₆ ^– anion is located outside the cavity, being centered between the primary hydroxyl faces of adjacent dimers. Eight water molecules of hydration per asymmetric unit reside in the spaces between the -CD columns. In view of the almost identical crystal data for2 a similar structure can be assumed for the cobaltocenium adduct.     

Synthesis and Crystal Structure Determination of 6-(N-Isopropyl)Amidino-2-Methylbenzothiazole Hydrochloride Monohydrate and 2-Amino-6-(N-Isopropyl)Amidinobenzothiazole Hydrochloride

Two novel substituted amidino-benzothiazoles 6-(N-isopropyl)amidino-2-methylbenzothiazole 4 and 2-amino-6-(N-isopropyl)amidinobenzothiazole 6 were prepared in multistep synthesis in form of hydrochloride salts. They were characterized by means of IR, ¹H, and ¹³C-NMR spectroscopy and elemental analysis. The crystal structures have been also determined by X-ray analysis. Both compounds crystallize as colorless prisms in the triclinic crystal system, space group P . Crystal data: (4) a = 8.741(4) Å, b = 9.602(7) Å, c = 9.946(2) Å, = 63.94(3)°, = 79.18(2)°, = 79.68(3)°, V = 732.1(6) ų, Z = R = 0.0396; a = 8.106(1) Å, b = 9.148(2) Å, c = 9.291(2) Å, = 104.83(1)°, = 103.36(2)°, = 90.62(1)°, V = 646.2(2) ų , Z = 2, R = 0.0376. The bond distances and angles in both structures are almost similar. Between these two structures was found the difference in the orientation of the 6-(N-isopropyl)amidino moiety with respect to the benzothiazole ring. In the crystal structures of the both compounds the intermolecular hydrogen bonds form three-dimensional networks.     

X-Ray Diffraction Analysis of Aluminum Hexamolybdenocobaltate(III) and Hexamolybdenocromate(III)

Isostructural crystals of aluminum hexamolybdenocobaltate(III) and hexamolybdenocromate(III) Al[MMo₆O₁₈(OH)₆] · 16H₂O (M = Co(III) and Cr(III)) were studied using X-ray diffraction analysis. These compounds crystallize in the triclinic system: space group P , Z = 1, (calcd) = 2.665 and 2.611 g/cm³, respectively. The unit cell parameters were determined: for aluminum hexamolybdenocobaltate(III), a = 6.796(1) Å, b= 11.248(2) Å, c = 11.568(2) Å; = 101.36(2)°, = 96.95(2)°, = 102.23(2)°; for aluminum hexamolybdenocromate(III), a = 6.838(1) Å, b = 11.312(2) Å, c = 11.605(2) Å; = 101.29(3)°, = 97.13(3)°, = 102.15(3)°.     

Crystal structure of copper(II) bis-hexafluoroacetylacetonate

An X-ray diffraction investigation has performed for copper(II) bis-hexafluoroacetylacetonate (Bruker AXS P4 automatic diffractometer, MoK radiation, t = –25°C). Crystal data for C₁₀H₂CuF₁₂O₄: a = 5.530(1) Å, b = 6.038(1) Å, c = 11.266(2) Å, = 95.948(3)°, = 101.743(3)°, = 92.298(3)°, space group; P1, V = 365.6(1) ų, Z = 1, d _calc = 2.169 g/cm³. The square-planar environment of the copper atom (Cu-O_av 1.912 Å, O-Cu-O_av 93°) is completed to bipyramidal by two fluorine atoms of the neighboring molecules, Cu...F 2.71 Å and 2.75 Å.Original Russian Text Copyright © 2004 by S. A. Gromilov, I. A. Baidina, P. A. Stabnikov, and G. V. RomanenkoTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 3, pp. 502–507, May–June 2004.     

The crystal structure of dibenzo-14-crown-4, a preorganized basis of square pyramid coordination for lithium ions

Dibenzo-14-crown-4 (DB14C4) has a high selectivity for Li⁺. The rigidity of the molecule caused by the two benzene rings suggests that this is a preorganized ligand for metal ions and particularly for Li⁺. A single crystal structure study of the molecule was performed. The crystal data are: space groupP2₁,a = 12.811(2),b = 5.106(1),c = 12.816(3)Å, = 115.44(1)°,V = 757.0(2)ų withZ = 2. The structure was refined toR = 0.049 andR _w, = 0.058 using 1804 unique data withF < 4(F). The conformation of the free ligand was found to be similar to that of the complexed ligand and the conformational parameters of the free ligand and its derivatives are compared to Li⁺ complexes of the ligand and its derivatives.This paper is dedicated to the memory of the late Dr C. J. Pedersen.     

Dissociation constants of the ampholyte glycine in 50 mass % methanol-water from 5 to 55°C,with related thermodynamic quantities

The two thermodynamic dissociation constants of glycine at 11 temperatures from 5 to 55°C in 50 mass % methanol-water mixed solvent have been determined from precise emf measurements with hydrogen-silver bromide electrodes in cells without liquid junction. The first acidic dissociation constant (K ₁)for the process HG⁺H⁺+G^± is expressed as a function ofT(^oK) by the equation pK ₁ = 2043.5/T – 9.6504 + 0.019308T. At 25°C, pK ₁is 2.961 in the mixed solvent, as compared with 2.350 in water, with H°=1497 cal-mole^–1, G°=4038 cal-mole^–1, S°=–8.52 cal-°K^–1-mole^–1, and C _p ^o =–53 cal-°K^–1-mole^–1. The second acidic dissociation constant (K ₂)for the process G^±H⁺+G^– over the temperature range studied is given by the equation pK ₂ = 3627.1/T – 7.2371 + 0.015587T. At 25°C, pK ₂is 9.578 in MeOH–H₂O as compared with 9.780 in water, whereas H° is 10,257 cal-mole^–1, G° is 13,063 cal-mole^–1, S° is –9.41 cal-°K^–1-mole^–1, and C _p ^o is –43 cal-°K^–1-mole^–1. The protonated glycine becomes weaker in 50 mass % methanol-water, whereas the second dissociation process becomes stronger despite the lower dielectric constant of the mixed solvent (=56.3 at 25°C).     

Complexation of uranium(VI) by salicylate and substituted salicylates: A kinetic study

Summary Kinetic studies on the complexation of uranium(VI) by salicylate and various substituted salicylates have been carried out using the stopped-flow spectrophotometric technique at pH 7.0–8.5 (NH₄OH+NH₄NO₃ buffer). Results are in conformity with a mechanism involving binding of UO₂OH⁺ species through the carboxylate group of the salicylate to form an inner-sphere species in a fast equilibrium (equilibrium constant=K) followed by a slow rate-determining ring closure (rate constant=k) involving loss of a molecule of water between the OH group bound to uranium(VI) and the phenolic group of the salicylate. The value of the equilibrium constant (K) obtained from the kinetic data in the case of 5-sulphosalicylate (log K=3.21 at 25 °C, I=1 M) is compatible with the literature thermodynamic value (log K = 3.89 at 25 °C, I=0.015 M). Increase in pH retards the reaction due to the equilibrium, UO₂OH⁺ + OH^– UO₂(OH)₂, the UO₂(OH)₂ being unreactive. The average value of K (log K=8.58 at 25°C, I=1M) obtained kinetically from the results of investigation with different ligands is also in good agreement with the literature thermodynamic value (log K= 8.8 at 25°C, I=0.1M). Both K and k are sensitive to the nature of the substituent in the benzene ring, decreasing with increasing acidity of the -CO₂H group of the salicyclic acid; the substituent effect is well demonstrated by the plot of log kversus _L (where ), which is linear. H^# and S^# values corresponding to k have been evaluated in each case. S^# values are all negative in conformity with ring closure in the rate-determining step.     

The 1,4,7,10,13-Pentaoxacyclohexadecane-14,16-Dione Complex with Potassium Thiocyanate: Crystal Structure

The complex of 1,4,7,10,13-pentaoxacyclohexadecane-14,16-dione (L) with potassium thiocyanate, C₁₁H₁₈O₇· KNCS (I), is prepared and characterized by X-ray diffraction analysis: space group C2/c, a = 26.810 Å, b = 7.834 Å, c = 20.504 Å, = 129.19°, Z = 8. The crystal structure is solved by the direct method and refined anisotropically by the full-matrix least-squares method to R = 0.038 for all 2929 unique measured reflections (CAD4 automated diffractometer, MoK ). Structure I is built of [KL(NCS)] monomers of the host–guest type, which are united into [K₂L₂(NCS)₂] dimers containing four-membered KNKN cycles. In the crystal, the dimers are united into infinite polymeric double chains (along the b axis) by K···O=C outer bonds. The K⁺ cation (CN 8) does not lie in the plane of the L crown ligand but is located above it. The coordination polyhedron of the K⁺ cation is irregular; its vertices are occupied by five ether O atoms of one L ligand, two N atoms of two SCN ligands, and one carbonyl O atom of the adjacent L ligand.     

Adhäsive Reibungselastizität von hartelastischem Polypropylen (HEPP)

Zusammenfassung Hartelastische Polymere, insbesondere hartelastisches Polypropylen (HEPP) zeigen neuartige mechanische Eigenschaften, die sich durch zwei hintereinandergeschaltete Kelvin-Elemente im wesentlichen beschreiben lassen. Die nachgewiesene Affintransformation bei der Verstreckung vereinfacht die Verhältnisse in entscheidender Weise. Das eine Kelvin-Element besteht aus einer Feder mit der FederkonstanteE und parallel geschaltetem Dämpfer mit der Viskosität, das andere aus einem Adhäsionsglied mit der rücktreibenden KraftK ₁, und einem parallel geschaltetem Reibungselement mit dem Reibungskoeffizienten Die Röntgenäquatorkleinwinkelstreuung verrät bei Verstreckung sich bildende Zwischenräume zwischen den Lamellen, deren Dickenzunahme gleich ist der wachsenden Langperiode, wobei in diesen Zwischenräumen unabhängig vom Verstreckungsgrad 50 Å dicke Fibrillen mit einem mittleren Abstand von 115 Å entstehen. Ihr hieraus berechnetes Gesamtvolumen ergibt sich auch aus Kernresonanzmessungen von bei — 60°C verstrecktem HEPP. Die bei konstanter Verstreckungsgeschwindigkeitv und anschließender Verkürzungsgeschwindigkeit —v aufgenommenen Kraft-DehnungskurvenK() zeigen sechs charakteristische Einzelabschnitte. Nach dem pseudo-Hooke'schen Anlaufgebiet, bedingt durch die RuhreibungK _a von treten zwei exponentiell sich einstellende Abschnitte 3 und 5 auf mit ähnlicher-Halbwertsbreite von ₀ 0,5 beim Verstrecken und ₀ 0,2 beim Zurückfahren. Auf Abschnitt 3 folgt ein Plateau, dessen Höhe vonv nur ganz wenig abhängt und eine gleitende Reibungv verrät. Die Durchrechnung zeigt, daß auch die ₀-Halbwertsbreiten durchv bestimmt sind. Die atomare Erklärung für die zurücktreibende KraftK ₁, vom zweiten Kelvin-Element ergibt sich durch eine an den lateralen Fibrillenoberflächen auftretenden Oberflächenenergie _l von 60 erg /cm² und eine bei Verstreckung an den Fibrillenaustrittsstellen auftretende Reibungv = 1,5 × 10⁷ dyn beiv = 1,5 × 10^–4 cm/sek undv = 2,3 × 10⁷ dyn beiv = 1,5 × 10^–2 cm/sek bei einer Präparatdicke von 0,03 cm² und einer Präparatlänge von 5,2 cm. Dies entspricht Austrittseschwindigkeiten von 6 × 10^–3 Å/sek bzw. 6 × 10^–1 Å/sek der Mikrofibrillen an den Mikroparakristalloberflächen. Die geringev-Abhängigkeit vonv verrit den Charakter einer gleitenden Reibung. Die Ruhreibung für dieses Präparat beträgt stets etwa 1,5 × 10⁷ dyn; die Adhäsionsspannung einer Mikrofibrille beträgt allgemein 5 × 10⁸ dyn/cm².

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Summary Hard elastic fibers, especially hard elastic polypropylene (HEPP) show novel mechanical properties which can be described with two Kelvin-elements in series. The affine transformation of the shape of the sample during straining simplifies the situation decisively. One of the Kelvin-elements consists of a spring-constantE, parallel with a dashpot with the viscosity. The other consists of an adhesive term with a retractive forceK ₁, in parallel with a friction term with the friction coefficient The small angle X-ray scattering on the equator reveals during straining an opening of gaps between lamellae. The increase of these gaps equals the increase of the long period. The gaps are bridged, independent from straining, by 50 Å thick fibrils with a mean distance of 115 Å. Their total volume calculated from these data is in good agreement with the results obtained from nuclear magnetic resonance (NMR) measurements on HEPP fibers strained at — 60°C. The stress-strain diagrams taken with constant strain velocitiesv and following destraining velocities —v show six characteristic sections. After the first pseudo-Hooke'ian section, limited by the static friction Ka, appear two exponential sections 3 and 5 with almost the same ₀-half width of ₀ 0,5 at straining and ₀ 0,2 at destraining. Section 3 is followed by a plateau varying only slightly, withv and reveals the sliding frictionv The calculations show that the ₀-half widths are determined also byv. An explanation in atomic scale for the driving forceK ₁ of the second Kelvin element is the lateral surface free energy of the fibrils _L of 60 erg cm^–2 and a sliding frictionv = 15 × 10⁷ dyn atv = 1,5 × 10^–4 cm/sec andv = 2,3 × 10⁷ dyn atv = 1,5 × 10^–2 cm/sec for a fibril which is 5,2 long at the beginning. The values imply a constant cross-section of the sample of 0,03 cm³. The relatively small dependence ofv onv reveals that it is a sliding friction with extruding velocities of 6 × 10^–3 Å/sec resp. 6 × 10^–1 Å/sec of the microfibrils from the lateral boundaries of the microparacrystals. The static friction of this sample isK _a = 1,5 × 10⁷ dyn, corresponding to an absolute value of 5 × 10⁸ dyn cm^–2 for the adhesive stress of on microfibril.

     

Tetrakis(2-fluorophenylamino)silan und sein erstes Kondensationsprodukt N-(2-fluorophenyl)-Si,Si, Si,Si′, Si′, Si′-hexakis(2-fluorophenylamino)-disilazan. Synthesen und Kristallstrukturen

Zusammenfassung Tetrakis(2-fluorophenylamino)silan (1) wurde als Precursor zur Darstellung poröser, nitridischer Festkörper synthetisiert und mit Hilfe der Einkristallröntgenstrukturanalyse charakterisiert (C2/c;a=16.771(7) Å,b=16.827(5) Å,c=16.753(6) Å, ß=111.00(2)°,z=8). Beim Erhitzen mit Ammoniumcarbamat als Katalysator wurde N-(2-fluorophenyl)-Si, Si, Si, Si, Si, Si, -hexakis(2-fluorophenylamino)disilazan (2) als erstes Kondensationsprodukt isoliert ( ;a=9.331(1) Å,b=13.698(5) Å,c=16.164(4) Å, =90.34(2)°, ß=103.03(2), =103.04(3)°, Z=2).

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Tetrakis(2-fluorophenylamino)silane and its first product of condensation N-(2-fluorophenyl-Si, Si, Si, Si, Si, Si-hexakis(2-fluorophenylamino)disilazane. Syntheses and crystal structures

Summary The synthesis and crystal structure determination of silanetetramine N,N,N,N2-fluorophenyl(C2/c;a=16.771(7) Å,b=16.827(5) Å,c=16.753(6) Å, ß=111.00(2)°, z=8) are reported. In a search for suitable condensation pathways to silicon/nitrogen based porous solids, N-(2-fluorophenyl)-Si,Si,Si,Si,Si,Si-hexakis(2-fluorophenylamino)disilazane (2) has been obtained from the ammonium carbamate catalyzed condensation of the silanetetramine in teflon lined autoclaves. The X-ray crystal structure determination ( ;a=9.331(1) Å,b=13.698(5) Å,c=16.164(4) Å, =90.34(2)°, ß=103.03(2)°, =103.04(3)°, Z=2) shows the disilazane to be a dimer formed by linear condensation from the monomeric silazane.

     

Synthesis,Physicochemical Properties,and Structure of Heterocyclic β-Aminovinyl Ketones and Related Copper(II) Complex

Heterocyclic -aminovinyl ketones (HL) and the copper complex CuL₂ are synthesized and studied by IR and ¹H NMR spectroscopies. The crystal structure of one of the tautomeric HL molecules is determined by X-ray diffraction analysis. The crystals are triclinic: a = 9.261(6) Å, b = 9.448(6) Å, c = 11.310(5) Å, = 96.74(5)°, = 99.46(5)°, = 93.60(5)°, space group P . The compound has the form of a ketoamine tautomer. The structure contains intramolecular and intermolecular hydrogen bonds. The latter link the molecules into the center-symmetric dimers.     

Synthese,Kristallstruktur und Konformation von N2-Dibenzyl-N1-t-butoxycarbonylhydrazin

Summary The synthesis and the crystal structure of N²-dibenzyl-N¹-butoxycarbonyl hydrazine are reported. The compound was prepared from commercially availablet-butyl carbazate. It crystallizes in the triclinic space group P 1 witha=5.479(1) Å,b=9.559(1) Å,c=9.748(1) Å,a=63.81(1)°, =87.52(1)°, =74.07(1) Å,Z=1,D=1.18 g/cm³. The structure was solved by direct methods and refined toR=0.0329.