4-Azidomethyl-7-methyl-2-oxo-2H-chromene-6-sulfonyl azide

In the title compound, C11H8N6O4S, the plane of the coumarin aromatic ring is twisted by 17.2 (2)degrees with respect to the plane of the azide group bound to the methylene substituent, whereas it is twisted by 83.2 (2)degrees to the plane of the azide attached to the sulfonyl group. The crystal structure is stabilized by weak C-H center dot center dot center dot O interactions, leading to the formation of dimers with R-2(2)(12) graph-set motifs. These dimers are further linked by weak S-O center dot center dot center dot pi and pi-pi contacts centroid-centroid distance = 3.765 (2) angstrom], leading to the formation of a layered structure.

Direct conversion of 13-beta-alkylgonatetraenes into 13-beta-alkylgon-4-en-3-ones

Birch reduction of 8,9-didehydroestradiol-17 beta 3-methyl ether 1 or 9(11)-didehydroestradiol-17 beta 3-methyl ether 2 followed by acid hydrolysis results in a mixture of 19-nortestosterone 8 and 19-nor-9 beta, 10 alpha-testosterone 9 in varying amounts. However, reduction of their acetates with sodium or lithium, tert-butyl alcohol in liquid ammonia and in the presence of aniline affords exclusively 19-nortestosterone. Similarly, 18a-homo-19-nortestosterone 12 is prepared from the acetate of 18a-homoestradiol-17 beta 3-methyl ether, 10.

Structure of 9[alpha],19-dihydroxy-4-androstene-3,17-dione

C19H26O4, M(r) = 318.41, orthorhombic, P2(1)2(1)2(1), a = 10.591 (1), b = 11.133 (1), c = 13.657 (2) angstrom, V = 1610.29 angstrom 3, Z = 4, D(m) (flotation in KI) = 1.301, D(x) = 1.313 g cm-3, Mo K-alpha, lambda = 0.7107 angstrom, mu = 0.85 cm-1, F(000) = 688, T = 293 K, R = 0.057 for 1253 significant reflections. The A ring is disordered with atoms C(2) and O(19) occupying two possible sites. The molecules are held together by a hydrogen bond [O(9)...O(17) = 2.89 angstrom].

Critical properties of the double-exchange ferromagnet Nd(0.6)Pb(0.4)MnO(3)

Results of a study of dc magnetization M(T,H), performed on a Nd(0.6)Pb(0.4)MnO(3) single crystal in the temperature range around T(C) (Curie temperature) which embraces the supposed critical region \epsilon\=\T-T(C)\/T(C)less than or equal to0.05 are reported. The magnetic data analyzed in the critical region using the Kouvel-Fisher method give the values for the T(C)=156.47+/-0.06 K and the critical exponents beta=0.374+/-0.006 (from the temperature dependence of magnetization) and gamma=1.329+/-0.003 (from the temperature dependence of initial susceptibility). The critical isotherm M(T(C),H) gives delta=4.54+/-0.10. Thus the scaling law gamma+beta=deltabeta is fulfilled. The critical exponents obey the single scaling equation of state M(H,epsilon)=epsilon(beta)f(+/-)(H/epsilon(beta+gamma)), where f(+) for T>T(C) and f(-) for T

Halogen Bonding and Structural Modularity in 2,3,4-and 3,4,5-Trichlorophenol

The crystal structure of 3,4,5-trichlorophenol contains hydrogen bonded domains that occur respectively in the structures of 4-chlorophenol and 3,5-dichlorophenol. Such modularity is also seen in 2,3,4-trichlorophenol. These structures, and those of the six isomeric dichlorophenols, illustrate the importance of halogen bonding as a structure determining interaction.

Ferromagnetic transition and specific heat of Pr(0.6)Sr(0.4)MnO(3)

The critical properties of orthorhombic Pr(0.6)Sr(0.4)MnO(3) single crystals were investigated by a series of static magnetization measurements along the three different crystallographic axes as well as by specific heat measurements. A careful range-of-fitting-analysis of the magnetization and susceptibility data obtained from the modified Arrott plots shows that Pr(0.6)Sr(0.4)MnO(3) has a very narrow critical regime. Nevertheless, the system belongs to the three-dimensional (3D) Heisenberg universality class with short-range exchange. The critical exponents obey Widom scaling and are in excellent agreement with the single scaling equation of state M(H,epsilon) = vertical bar epsilon vertical bar(beta) f(+/-)(H/vertical bar epsilon vertical bar((beta+gamma)); with f(+) for T > T(c) and f(-) for T < T(c). A detailed analysis of the specific heat that account for all relevant contributions allows us to extract and analyze the contribution related to the magnetic phase transition. The specific heat indicates the presence of a linear electronic term at low temperatures and a prominent contribution from crystal field excitations of Pr. A comparison with data from literature for PrMnO(3) shows that a Pr-Mn magnetic exchange is responsible for a sizable shift in the lowest lying excitation.

Structural and dielectric behavior of pulsed laser ablated Sr(0.6)Ca(0.4)TiO(3) thin film and asymmetric multilayer of SrTiO(3) and CaTiO(3)

Homogeneous thin films of Sr(0.6)Ca(0.4)TiO(3) (SCT40) and asymmetric multilayer of SrTiO(3) (STO) and CaTiO(3) (CTO) were fabricated on Pt/Ti/SiO(2)/Si substrates by using pulsed laser deposition technique. The electrical behavior of films was observed within a temperature range of 153 K-373 K. A feeble dielectric peak of SCT40 thin film at 273 K is justified as paraelectric to antiferroelectric phase transition. Moreover, the Curie-Weiss temperature, determined from the epsilon'(T) data above the transition temperature is found to be negative. Using Landau theory, the negative Curie-Weiss temperature is interpreted in terms of an antiferroelectric transition. The asymmetric multilayer exhibits a broad dielectric peak at 273 K. and is attributed to interdiffusion at several interfaces of multilayer. The average dielectric constants for homogeneous Sr(0.6)Ca(0.4)TiO(3) films (similar to 650) and asymmetric multilayered films (similar to 350) at room temperature are recognized as a consequence of grain size effect. Small frequency dispersion in the real part of the dielectric constants and relatively low dielectric losses for both cases ensure high quality of the films applicable for next generation integrated devices. (C) 2011 Elsevier B.V. All rights reserved.

New Structural Topologies in a Series of 3d Metal Complexes with Isomeric Phenylenediacetates and 1,3,5-Tris(1-imidazolyl)benzene Ligand: Syntheses, Structures, and Magnetic and Luminescence Properties

In this article we present the syntheses, characterizations, magnetic and luminescence properties of five 3d-metal complexes, Co(tib)(1,2-phda)](n)center dot(H2O)(n) (1), Co-3(tib)(2)(1,3-phda)(3)(H2O)](n)center dot(H2O)(2n) (2), Co-5(tib)(3)(1,4-phda)(5)(H2O)(3)](n)center dot(H2O)(7n) (3), Zn-3(tib)(2)(1,3-phda)(3)](n)center dot(H2O)(4n) (4), and Mn(tib)(2)(H2O)(2)](n)center dot(1,4-phdaH)(2n)center dot(H2O)(4n) (5), obtained from the use of isomeric phenylenediacetates (phda) and the neutral 1,3,5-tris(1-imidazolyl)benzene (tib) ligand. Single crystal X-ray structures showed that 1 constitutes 3,5-connected 2-nodal nets with a double-layered two-dimensional (2D) structure, while 2 forms an interpenetrated 2D network (3,4-connected 3-nodal net). Complex 3 has a complicated three-dimensional structure with 10-nodal 3,4,5-connected nets. Complex 4, although it resembles 2 in stoichiometry and basic building structures, forms a very different overall 2D assembly. In complex 5 the dicarboxylic acid, upon losing only one of the acidic protons, does not take part in coordination; instead it forms a complicated hydrogen bonding network with water molecules. Magnetic susceptibility measurements over a wide range of temperatures revealed that the metal ions exchange very poorly through the tib ligand, but for the Co(II) complexes the effects of nonquenched orbital contributions are prominent. The 3d(10) metal complex 4 showed strong luminescence with lambda(max) = 415 nm (lambda(ex) = 360 nm).

Polymorphism and Phase Transformation Behavior of Solid Forms of 4-Amino-3,5-dinitrobenzamide

We report the preparation, analysis, and phase transformation behavior of polymorphs and the hydrate of 4-amino-3,5-dinitrobenzamide. The compound crystallizes in four different polymorphic forms, Form I (monoclinic, P2(1)/n), Form II (orthorhombic, Pbca), Form III (monoclinic, P2(1)/c), and Form IV (monoclinic, P2(1)/c). Interestingly, a hydrate (triclinic, P (1) over bar) of the compound is also discovered during the systematic identification of the polymorphs. Analysis of the polymorphs has been investigated using hot stage microscopy, differential scanning calorimetry, in situ variable-temperature powder X-ray diffraction, and single-crystal X-ray diffraction. On heating, all of the solid forms convert into Form I irreversibly, and on further heating, melting is observed. In situ single-crystal X-ray diffraction studies revealed that Form II transforms to Form I above 175 degrees C via single-crystal-to-single-crystal transformation. The hydrate, on heating, undergoes a double phase transition, first to Form III upon losing water in a single-crystal-to-single-crystal fashion and then to a more stable polymorph Form I on further heating. Thermal analysis leads to the conclusion that Form II appears to be the most stable phase at ambient conditions, whereas Form I is more stable at higher temperature.

Dual Stress and Thermally Driven Mechanical Properties of the Same Organic Crystal: 2,6-Dichlorobenzylidene-4-fluoro-3-nitroaniline

An elastic organic crystal, 2,6-dichlorobenzylidine-4-fluoro-3-nitroaniline (DFNA), which also shows thermosalient behavior, is studied. The presence of these two distinct properties in the same crystal is unusual and unprecedented because they follow respectively from isotropy and anisotropy in the crystal packing. Therefore, while both properties lead from the crystal structure, the mechanisms for bending and thermosalience are quite independent of one another. Crystals of the low-temperature (a) form of the title compound are bent easily without any signs of fracture with the application of deforming stress, and this bending is within the elastic limit. The crystal structure of the a-form was determined (P2(1)/c, Z = 4, a = 3.927(7) angstrom, b = 21.98(4) angstrom, c = 15.32(3) angstrom). There is an irreversible phase transition at 138 degrees C of this form to the high-temperature beta-form followed by melting at 140 degrees C. Variable-temperature X-ray powder diffraction was used to investigate the structural changes across the phase transition and, along with an FTIR study, establishes the structure of the beta-form. A possible rationale for strain build-up is given. Thermosalient behavior arises from anisotropic changes in the three unit cell parameters across the phase transition, notably an increase in the b axis parameter from 21.98 to 22.30 angstrom. A rationale is provided for the existence of both elasticity and thermosalience in the same crystal. FTIR studies across the phase transition reveal important mechanistic insights: (i) increased pi...pi repulsions along 100] lead to expansion along the a axis; (ii) change in alignment of C-Cl and NO2 groups result from density changes; and (iii) competition between short-range repulsive (pi...pi) interactions and long-range attractive dipolar interactions (C-Cl and NO2) could lie at the origin of the existence of two distinctive properties.

中空纤维膜基萃取稀土的研究：中空纤维膜基萃取Ce~(4+), Th~(4+)和RE~(3+)及其传质动力学

本文用中空纤维膜基萃取法研究了铈（IV）、钍和 RE（III）的膜基萃取；铈（IV）与 RE（III）、钍和 RE（III）的膜基萃取分离；铈（IV）与 RE（III）的界面化学反应动力学；膜基萃取中的流体动力学；萃取操作中乳化发生的机理；测定了中空纤维膜的孔率和孔径。在铈（IV）、钍和 RE（III）的膜基萃取过程中，研究了水相流量、油相流量、原料液中硫酸浓度、萃取剂 N1923浓度和水相溶质浓度对基于水相总传质系数的影响。钍的总传质系数受水相流量影响较大，不受油相流量影响，从而提出水相扩散层控制的膜基萃取传质机理；铈（IV）的传质系数受水相流量影响，油相流量影响较小，主要为水相扩散层控制的传质机理；RE（III）的传质系数受水相和油相的影响都比较小，为膜内传质过程的传质机理。酸浓度对钍和铈（IV）传质系数影响较小，是由于酸浓度影响分配系数，而对于水相扩散控制的传质过程，水相分传质系数与分配系数无关；酸浓度对 RE（III）的影响，是由于膜内传质阻力与分配系数在关；N1923 对 RE（III）萃取传质系数的影响进一步证明膜内过程控制的传质机理，同时对数曲线的斜率大于1 也说明界面反应为一复杂过程；水相溶质浓度不影响基于水相的总传质系数，进一步证实了传质速度与初始浓度无关，也从一个侧面反应了膜基萃取实验有较好的重复性。实验研究的结果，对铈（IV）的膜基萃取选择油相组成为 10%N1923+4%异辛醇+正庚烷（或煤油），水相酸浓度为 1～2mol/L，水相和油相流量可以在较大的范围内选择；钍的膜基萃取条件相似，只是油组成中萃取剂浓度为 1%N1923。在流体动力学部分，通过作用力分析，利用能量守恒原理，推导出了膜基萃取操作中的雷诺数，建立了层流流动模型；腔内外流体流速的径向分布模型和平均流速的计算式；腔内外压力沿管长度分布的数学模型，并得到了两相流体的压力差计算式。流体的动力学分析对于研究乳化发生的机理、传质的数学模型和扩散层厚度等皆有理论价值。通过流体动力学理论，结合膜破裂压和界面张力的实验方法研究了乳化发生的机理。水相进入有机相的乳化，对于非同级萃取，外压作用是乳化的主要原因，提出了类似于重力液滴形成的乳化模型；对于有机相进入水相的乳化，亲油膜的表面易形成油膜及界面张力形成的附加压力是乳化的基本原因，而随着有机相内溶质浓度增加界面张力降低使乳化在萃取操作的后期较易发生。膜破裂压和界面张力的研究方法使乳化的研究变得可以进行实验测定，这对于膜材的选择是很有价值的。界面反应动力学采用了上升单滴法，这种方法一般具有实验重复性较差的缺点。通过实验发现，影响重复性的因素主要是单滴形成速率的稳定性、聚结界面处油水界面位置的恒定和扩散传质的消除等。我们采用盘管式油加液管的设计，比较简单地解决了单滴形成速率稳定的问题，油水界面恒定是一个技术性问题，在实验中得到了较好的解决，通过传质时间与控制聚结界面的面积解决了消除扩散传质的难题。本论文的创新之处有如下几个方面：1．根据氟碳铈矿中钍、铈（IV）与稀土（III）分离的总目标，首次实现了伯胺 N1923对上述离子的中空纤维膜基萃取，提出了利用动力学差异的新型分离模式；2．对流量改变对传质系数的影响，所有文献报道的流量范围都没有达到流量增加使传质系数减小，而这一较高的流量揭示了油水界面随压力增加向膜内移动的事实，这对防止乳化时的压力控制是非常重要的。流量对扩散层厚度影响是对传质系数影响的主要原因，而混流的影响是次要的因素；3．铈（IV）和 RE（III）、钍和 RE（III）的分离表明，分离系数远远大于由总传质系数预计的结果，从而提出了动力学竞争萃取分离的机理；4．膜破裂压的测定方法是一个创新的设计。这种方法对于膜材选择和萃取时操作压力的控制是非常重要的。在现有文献中，都是直接在膜萃取操作时测定水相中的游离油或油相中游离水的体积的方法进行研究，这即不能研究乳化的机理，也不能测定准确的乳化时间。因此膜破裂压测定为乳化过程提供了一个新的研究方法；5．乳化机理的研究得到了较新的结论，尤其对于油相进入水相的乳化机理，较好地解释了在水相有超压存在下油相漏液的原因；6．界面反应动力学实验装置中盘管式油相加样解决了油滴形成稳定性的问题，提高了实验测定的可靠性的重复性。