Pacharin: a new dibenzo(2,3-6,7)oxepin derivative from bauhinia racemosa lamk

The isolation of resveratrol and a new dibenzoxepin derivative, pacharin, from the heartwood of $\text{Bauhinia}$$\text{racemosa}$ Lank is reported. The structure of pacharin has been established as l,7-dlhydroxy-3-methoxy-2-methyl-dibenzo(2,3-6,7) oxepin (Va) by a study of its chemical and spectroscopic properties, including X-ray analysis.     

Syntheses, properties and structures of copper and nickel complexes of 6,7-dihydro-5H-1,4-dithiepin-2,3-dithiolate

The reaction of CuCl2-2H2O or NiCl2.6H2O with K2(C5H6S4) [potassium salt of 6,7-dihydro-5H-1,4-dithiepin-2,3-dithiolate] under nitrogen atmosphere resulted in the isolation of [Cu(C5H6S4)2]- or [Ni(C5H6S4)2]- as the tetrabutylammonium salt. Both complexes show characteristic IR and UV-Vis absorptions of transition metal dithiolenes. Cyclic voltammograms contain two waves indicating a two step electrochemical procedure [M(C5H6S4)2]0 = [M(C5H6S4)2]1-= [M(C5H6S4)2]2-. Single crystal structure study has been carried out on the nickel complex. Crystal of [Bu4N][Ni(C5H6S4)2] belongs to monoclinic space group P21/c with a=17.576(5), 6=10.883(2), c=17.773(4) A,B=91.07(2)0, Z=4, and o(calcd.)=1.348 g/cm3. Final result is R=0.059 for 2959 reflections. The NiS4 core exhibits square planar coordination with average Ni-S bond length of 2.134(5) A. There are not anion pairs in crystal. The anions stack along a and c axes while the cations intercalate in them. The nearest S-S contact is 4.429 A. The solid powder ESR s     

Rhenium oxohalides: synthesis and crystal structures of ReO3Cl(THF)2, ReOCl4(THF), Re2O3Cl6(THF)2, and Re2O3Cl6(H2O)2

Convenient methods to prepare solvated rhenium oxochlorides are described; these compounds should serve as useful starting materials for rhenium chemistry. Treatment of perrhenic acid, HReO(4), with chlorotrimethylsilane or with thionyl chloride, followed by addition of tetrahydrofuran, forms the new oxochloride complexes ReO(3)Cl(THF)(2) and ReOCl(4)(THF), respectively. Small amounts of two dinuclear oxochlorides, which evidently resulted from adventitious hydrolysis, were also isolated: Re(2)O(3)Cl(6)L(2), where L = THF or H(2)O. All four compounds were characterized by X-ray crystallography. The rhenium(vii) complex ReO(3)Cl(THF)(2) adopts a distorted octahedral geometry in which the three oxo ligands are in a facial arrangement; the rhenium(vi) complex ReOCl(4)(THF) adopts a trans octahedral structure. The two dinuclear rhenium(vi) compounds both have a single, nearly linear, bridging oxo group; on each Re center, the three terminal chlorides adopt a mer arrangement, and the terminal oxo and the coordinated Lewis base are mutually trans. The water ligand in the aqua complex is hydrogen bonded to nearby THF molecules. IR data are given.     

W2Cl7(CCl), a Polymeric Tungsten Chlorocarbyne Complex

Black crystals of W₂Cl₇(CCl) were obtained from the reaction of WCl₆ and As in CCl₄ at 250 °C under solvothermal conditions. The crystal structure (orthorhombic, space group Pbca, a = 1196(1), b = 1215.6(7), c = 1584(1) pm, Z = 8) is built of infinite zig‐zag chains of dinuclear complexes connected via bridging Cl atoms. The individual complexes are face‐sharing double octahedra concatenated via bridging Cl ligands. Each W atom is in a distorted octahedral coordination environment of five Cl atoms an the carbon atom of the μ₂ bridging chloromethylidyne ligand leading to the formula [{Cl₂W(μ‐CCl)(μ₂‐Cl)₂WCl₂}(μ‐Cl)]_n. The short W‐W distance of 256 pm indicates a multiple W‐W bond, the W‐C bonds of 195 pm are in the typical range for μ₂‐alkylidyne ligands, the C‐Cl bond of 167 pm is consistent with a sp¹ hybridisation on the carbon atom.     

New layered rubidium rare-earth selenides: syntheses,structures, physical properties,and electronic structures for RbLnSe(2)

The compounds RbLnSe(2) (Ln = La, Ce, Pr, Nd, Sm, Gd, Tb, Ho, Er, Lu) have been synthesized by means of the reactive flux method at 1173 K. These isostructural compounds, which have the alpha-NaFeO(2) structure type, crystallize with three formula units in space group D(3d)(5)-R(-)3m of the trigonal system in cells at T = 153 K of dimensions (a, c in A) La, 4.4313(4), 23.710(3); Ce, 4.3873(3), 23.656(3); Pr, 4.3524(11), 23.655(7); Nd, 4.3231(5), 23.670(4); Sm, 4.2799(4), 23.647(3); Gd, 4.2473(7), 23.689(5); Tb, 4.2197(4), 23.631(3); Ho, 4.1869(6), 23.652(5); Er, 4.1541(8), 23.576(7); Lu, 4.1294(6), 23.614(5). The structure consists of close-packed Se layers in a pseudocubic structure distorted along [111]. The Rb and Ln atoms occupy distorted octahedral sites in alternating layers. The Rb-centered octahedra share edges with the Ln-centered octahedra between layers. Within a given layer, both the Rb-centered and Ln-centered octahedra share edges with themselves. RbTbSe(2) and RbErSe(2) exhibit Curie-Weiss paramagnetism between 5 and 300 K, and RbCeSe(2) exhibits Curie-Weiss paramagnetism between 100 and 300 K. The optical transitions for RbCeSe(2), RbTbSe(2), and RbErSe(2) are in the 2.0-2.2 eV region of the spectrum, both from diffuse reflectance spectra and from first-principles calculations. These calculations also provide insight into the electronic structures and chemical bonding in RbLnSe(2). A quadratic fit for the lanthanide contraction of the Ln-Se distance is superior to the linear one only if the closed-shell atoms La and Lu are included.     

New Cu(II), Co(II), and Ni(II) complexes with thieno[2,3-b]pyridine and 2-methylthieno[2,3-b]pyridine as ligands: Synthesis and crystal structures

Although thienopyridines attract attention because of their biological activities, they have not been used as ligands in coordination compounds. Thieno[2,3-b]pyridine was prepared by known procedures; by reduction of 2-nitrothiophene, and reaction of the resulting 2-thienyl ammonium salt with malondialdehyde tetramethylacetal in the presence of zinc chloride. The same procedure was used for the preparation of a new derivative, 2-methylthieno[2,3-b]pyridine, starting from 2-methyl-5-nitrothiophene. The thienopyridines were used in the synthesis of coordination compounds. Chlorides, isothiocyanates, acetates, and chloroacetates of copper(II), nickel(II), or cobalt(II) were used as starting salts. The prepared complexes were characterized by elemental analysis and FT IR. Structures of the four complexes were determined by single-crystal X-ray diffraction analysis. Presented at the 1st International Conference “Applied Natural Sciences” on the occasion of the 10th anniversary of the University of Ss. Cyril and Methodius, Trnava, 7–9 November 2007.     

Non-classical heteroacenes: synthesis and properties of anthra[2,3-c:6,7-c']dithiophene derivatives

A new class of linear heteroacenes, anthra[2,3-c:6,7-c']dithiophenes, containing non-classical (non-Kekulé) thiophene in a 22-electron π-conjugated system have been prepared by electrochemical reduction. The electronic properties have been studied by DFT calculations and spectroelectrochemistry, supporting the formation of a triplet electronic structure.     

Crystal structure and physical properties of conducting molecular antiferromagnets with a halogen-substituted donor: (EDO-TTFBr2)2FeX4 (X = Cl, Br)

The crystal structure and physical properties of radical ion salts (EDO-TTFBr2)2FeX4 (X = Cl, Br) based on halogen-substituted organic donor and magnetic anions are investigated, including the comparison with the isomorphous compounds (EDO-TTFBr2)2GaX4 with nonmagnetic anions. The crystal structure of these four salts consists of uniformly stacked donor molecules and tetrahedral counter anions, and the Br substituents of the donor molecules are connected to halide ligands of anions with remarkably short intermolecular atomic distances. These salts show metallic behavior around room temperature and undergo a spin-density-wave transition in the low-temperature range, as confirmed with the divergence of the electron spin resonance (ESR) line width. Although close anion-anion contacts are absent in these salts, the FeCl4 salt undergoes an antiferromagnetic transition at TN = 4.2 K, and the FeBr4 salt shows successive magnetic transitions at TN = 13.5 K and TC2 = 8.5 K with a helical spin structure as a candidate for the ground state of the d-electron spins. The magnetoresistance of the FeCl4 salt shows stepwise anomalies, which are explained qualitatively using a pi-d interaction-based frustrated spin system model composed of the donor pi-electron and the anion d-electron spins. Although on the ESR spectra of the FeX4 salts signals from the pi- and d-electron spins are separately observed, the line width of the pi-electron spins broadens under the temperature where the susceptibility deviates from the Curie-Weiss behavior, showing the presence of the pi-d interaction.     

2,3-二硫苄基-6,7-二(2-氰基乙硫基)四硫富瓦烯的合成及其性质研究

设计合成了2,3-二硫苄基-6,7-二(2-氰基乙硫基)四硫富瓦烯. 以UV-Vis, ¹H NMR, IR, MS和元素分析进行了表征, 测定了产物的循环伏安图. 运用Gaussian 98量子化学程序包, 采用密度泛函 (DFT) 的方法, 在B3LYP/6-31G(d) 水平上对分子的几何构型进行了优化. 计算结果表明, 由于取代基的引入使体系的HOMO能量降低, 分子趋于稳定, 这与分子的设计是一致的.     

Metal vs ligand reduction in complexes of 1,3-dimethylalloxazine (DMA) with copper(I), ruthenium(II), and tungsten(VI). Crystal structures of (DMA)WO2Cl2 and (bis(1-methylimidazol-2-yl)ketone)WO2Cl2

The complexes [(DMA)Cu(PPh3)2](BF4) (1) (DMA = 1,3-dimethylalloxazine), [(DMA)Ru(bpy)2](PF6)2 (2), and (DMA)WO2Cl2 (3) were obtained as O4-N5-chelated species, as evident from an X-ray crystal structure analysis for 3 and from spectroscopy (NMR, IR, and UV-vis spectroelectrochemistry) for 1 and 2. The tungsten(VI) center in 3 has its oxide ligands in a cis/equatorial position and the chloride ligands in a trans/axial position; it also exhibits a relatively short bond to O4 (2.232(3) A) and a very long bond to N5 (2.462(3) A). Comparison with the new structurally characterized compound (BIK)WO2Cl2 (4) (BIK = bis(1-methylimidazol-2-yl)ketone), which has W-N bonds of about 2.30 A, confirms the unusual length of the W-N bond in 3, probably caused by repulsion between one of the oxo ligands and the peri-hydrogen atom (H6) of DMA. One-electron reduction of the complexes occurs reversibly at room temperature in THF (1, 2) or at 198 K in CH2Cl2 (3). EPR spectroscopy reveals that this process is ligand-centered for 1 and 2 but metal-centered for 3. Density functional methods and ab initio methodology are used to illustrate the correspondence in spin distribution between the radical anion pi systems of alloxazine and isoalloxazine ("flavosemiquinone").     

Investigations on the synthesis, structures, and properties of new copper(I) 2,3-dimethylpyrazine coordination compounds

Five new coordination compounds were prepared, structurally characterized, and investigated for their thermal properties. In the structure of the ligand-rich 4:9 compound, tetra(mu2-chloro)bis(mu2-2,3-dimethylpyrazine-N,N')tetrakis(2,3-dimethylpyrazine-N)tetracopper(I) tris(2,3-dimethylpyrazine)solvate (I), discrete complexes are formed by build up of two [(CuCl-(2,3-dimethylpyrazine)2]2 dimers, which are connected by two 2,3-dimethylpyrazine ligands via mu-N,N' coordination. In the 1:1 compound poly[mu2-chloro-mu2-2,3-dimethylpyrazine-N,N'-copper(I)] (II), (CuCl)2 dimers are found, which are connected by the 2,3-dimethylpyrazine ligands into layers. For this composition, a second polymorphic modification was found (III), which exhibits a different topology of the coordination network and a different packing of the layers. In the most stable 3:2 compound catena[tri(mu2-chloro)bis(mu2-2,3-dimethylpyrazine-N,N')tricopper(I)] (IV), six-membered rings of (CuCl)3 are found, which are connected by the 2,3-dimethylpyrazine ligands into chains. In the ligand-deficient 2:1 compound, poly[di(mu3-chloro)(mu2-2,3-dimethylpyrazine-N,N')dicopper(I)] (V), CuCl double chains are found, which are connected by the 2,3-dimethylpyrazine ligands into layers. On heating, compound I transforms quantitatively into the 3:2 compound IV without the formation of II or III as intermediates. Compound IV is also obtained by heating either the 1:1 compound II or III. On further heating, the 3:2 compound IV loses additional ligands, forming the ligand-deficient 2:1 compound V, which then decomposes into CuCl. The stability, thermal reactivity, and the transition behavior of all compounds were investigated using different thermoanalytical methods. These results are compared with those previously reported for the structurally similar CuCl(2-ethylpyrazine) coordination compounds. The formation and the stability of the different compounds in solution were also investigated.     

Synthesis,structures and luminescence of two new Europium(II) Silicate-Chlorides,Eu2SiO3Cl2 and Eu5SiO4Cl6

Eu₂SiO₃Cl₂ and Eu₅SiO₄Cl₆ were prepared by reaction of EuCl₂ with EuSiO₃ and Eu₂SiO₄, respectively, Sr₂SiO₃Cl₂: Eu²⁺ from mixtures of SrCO₃, Eu₂O₃, SrCl₂ · 6H₂O and SiO₂ under reducing conditions. The crystal structures of Eu₂SiO₃Cl₂ [a = 1118.7(5), c = 952.6(1) pm, tetragonal, I4/m, Z = 8, R = 3.3, R_w = 3.0%] and Eu₅SiO₄Cl₆ [a = 900.4(1), b = 1401.7(2), c = 1112.3(2) pm, β = 103.51(1)°, monoclinic, C2/c, Z = 4, R = 3.6, R_w = 2.6%] were determined from four-circle diffractometer data and compared with related compounds. The luminescence properties were investigated at 300 K and at 4.2 K; all compounds show intense bluish-green photoluminescence. Sr₂SiO₃Cl₂:Eu²⁺ shows thermoluminescence.     

Diphenyldichlorophosphonium trichloride-chlorine solvate 1:1, [PPh2Cl2]+Cl(3)(-).Cl2: an ionic form of diphenyltrichlorophosphorane. Crystal structures of [PPh2Cl2]+Cl(3)(-).Cl2 and [(PPh2Cl2)+]2[InCl5](2-)

An ionic form of diphenyltrichlorophosphorane, namely, diphenyldichlorophosphonium trichloride isolated as a dichlorine solvate (1), was obtained by treating PPh(2)Cl(3) with excess chlorine. The identity of this species was established by single-crystal X-ray analysis and (31)P, (1)H, and (35)Cl NMR and Raman spectra. Bis(diphenyldichlorophosphonium) pentachloroindate (2) was obtained by the reaction of diphenyltrichlorophosphorane with indium trichloride in dichloromethane for comparison purposes. Its identity was determined by (31)P NMR spectra and single-crystal X-ray analysis.     

Zinc and cobalt complexes with (2-carboxyphenoxy) acetic acid ligand: syntheses,structures, fluorescent and magnetic properties

Four binary compounds, [Zn(cpa)(H₂O)₃] (1), [Co(cpa)(H₂O)₃] (2), [Zn(cpa)(H₂O)]_n, (3) and [Co(cpa)(H₂O)]_n (4) (H₂cpa = (2-carboxyphenoxy)acetic acid), have been synthesized and structurally characterized. In mononuclear 1 or 2, the metal ion (Zn^II for 1 and Co^II for 2) is surrounded by three water molecules and one tridentate chelate cpa^2? in a distorted octahedral geometry, while in 3 or 4, the central metal ion (Zn^II for 3 and Co^II for 4) is located in a deformed square–pyramid formed by one water and two cpa^2?. Each cpa^2? is chelate bridging μ₂ coordination and forms a 1-D zigzag chain structure 2 or 3. The different synthesis conditions for 1–4 have been carefully discussed. The solid-state fluorescence measurements for 1 and 3 together with magnetic properties for 4 also have been investigated.