共查询到20条相似文献,搜索用时 31 毫秒
1.
Ng Seik Weng~* 《结构化学》2000,(6)
1 INTRODUCTIONSeveralincorrectspacegroupshavebeenre assignedbymakinguseofsimulatedstructurefactors;however,thecruxofthisoranyspacegrouprevisionistheaccuratereportingofthespacegroupandatomiccoordinatesoftheincorrectlydeterminedstructuresincethetruestruc… 相似文献
2.
用X-射线晶体结构衍射法测定了〔C5H4C(CH3)2CH2CH=CH2〕Sm(OH)Cl·2MgCl2·4THF的晶体结构。它属三斜晶系,空间群为P1,a=10.773(2),b=12.836(3),c=15.478(3),α=111.46(3),β=107.71(3),γ=92.54(3)°,V=1868(1)3,Mr=827.91,Dx=1.472g/cm3,μ=2.0006mm-1,F(000)=840,Z=2,R=0.041,wR=0.050(I≥3σ(I))。分子中Sm原子的配位数为8,形成一个严重扭曲的八面体结构;2个Mg原子的配位情况相似,它们的配位数都是6,分别构成2个扭曲的八面体。这3个八面体通过3个共平面联接 相似文献
3.
Elschenbroich C Plackmeyer J Nowotny M Behrendt A Harms K Pebler J Burghaus O 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(24):7427-7439
Five new paramagnetic dinuclear complexes containing [5]trovacenyl groups, (eta7-C7H7)V(eta5-C5H4-), have been prepared and characterized, including by single-crystal X-ray diffraction. As intervening spacers, ethenediyl units in the geminal and vicinal (Z)- and (E)-bridging modes as well as methanediyl and ethanediyl units have been included with the aim of studying their propensity to transmit electric and magnetic information. It is found that redox splitting of consecutive electron-transfer steps is resolved for reduction (0-->1- -->2-) only, unsaturation of the C2 bridge not being requisite, since the -CH2CH2- spacer also gives rise to a small redox splitting. Magnetic communication is quantified in terms of the exchange coupling constant J, accessible from the EPR hyperfine pattern in solution and from magnetic susceptometry in the solid state. The results obtained from these methods generally differ; this fact is not surprising in view of conformational differences in the respective states of aggregation. It is concluded that orientation-dependent mechanisms of spin-spin interactions (pi-orbital overlap, hyperconjugation) contribute extensively although, as implied by sizeable J values for -CH2- and -C2H4- linked di[5]trovacenyl groups, coupling mediated by the sigma-orbital chain must also be considered. 相似文献
4.
William T. A. Harrison 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(5):m205-m208
The scandium(III) cations in the structures of pentaaqua(biuret‐κ2O,O′)scandium(III) trichloride monohydrate, [Sc(C2H5N3O2)(H2O)5]Cl3·H2O, (I), and tetrakis(biuret‐κ2O,O′)scandium(III) trinitrate, [Sc(C2H5N3O2)4](NO3)3, (II), are found to adopt very different coordinations with the same biuret ligand. The roles of hydrogen bonding and the counter‐ion in the establishment of the structures are described. In (I), the Sc3+ cation adopts a fairly regular pentagonal bipyramidal coordination geometry arising from one O,O′‐bidentate biuret molecule and five water molecules. A dense network of N—H...Cl, O—H...O and O—H...Cl hydrogen bonds help to establish the packing, resulting in dimeric associations of two cations and two water molecules. In (II), the Sc3+ cation (site symmetry 2) adopts a slightly squashed square‐antiprismatic geometry arising from four O,O′‐bidentate biuret molecules. A network of N—H...O hydrogen bonds help to establish the packing, which features [010] chains of cations. One of the nitrate ions is disordered about an inversion centre. Both structures form three‐dimensional hydrogen‐bond networks. 相似文献
5.
《Journal of Coordination Chemistry》2012,65(14):1609-1614
Two new uranyl complexes [UO2(DPDPU)2(NO3)2](C6H5CH3) (1) and [UO2(PMBP)2 (DPDPU)](CH3C6H4CH3)0.5 (2), (DPDPU?=?N,N′-dipropyl-N,N′-diphenylurea, HPMBP?= 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5) were synthesized and characterized. The coordination geometry of the uranyl atom in 1 is distorted hexagonal bipyramidal, coordinated by two oxygen atoms of two DPDPU molecules and four oxygen atoms of two bidentate nitrate groups. The coordination geometry of the uranyl atom in 2 is distorted pentagonal bipyramidal, coordinated by one oxygen atom of one DPDPU molecule and four oxygen atoms of two chelating PMBP molecules. 相似文献
6.
1 INTRODUCTION Synthesis of transition metal complexes with Schiff-base has been a subject of considerable importance [1,2]. They are not only good complexing agents for Schiff-base, but also good bactericide and antitumour agent [3,4]. At present, there is a spectacular growth in this field. Recently, some bridged binuclear complexes have received much attention on account of their biological relevance and condensed-phase magnetic properties[5,6]. Especially, the complexes containin… 相似文献
7.
DSC measurements were carried out for [Ni(H2O)6](ClO4)2 (sampleH) and [Ni(D2O)6](ClO4)2 (sampleD) in the temperature range 300–380 K. For both compounds two anomalies on the DSC curves were detected. The results for sampleH are compared to those previously obtained using adiabatic calorimetry method. For both compounds studied in this work the high-temperature transition appears at the same temperature while the low-temperature one is shifted towards higher temperatures in sampleD. Disorder connected with H2O or D2O groups is suggested in the intermediate phase between the low- and high-temperature transitions. 相似文献
8.
Phase transitions of polycrystalline [Fe(H2O)6](ClO4)3 and [Cr(H2O)6](ClO4)3 studied by DSC 总被引:1,自引:0,他引:1
Mikuli E. Grad B. Zaremba K. Wróbel S. 《Journal of Thermal Analysis and Calorimetry》2004,76(3):719-726
The effects of heat treatment on soymilk protein denaturation were studied by differential scanning calorimetry (DSC) and
electrophoresis. Transition behavior of soymilk was studied by DSC. Three endotherms were found in DSC heating curves; the
transition observed at around 70°C is attributed to the denaturation of 7S (b-conglycinin) and the transition at around 90°C
is to 11S (glycinin). The denaturation temperature increased with the increasing soymilk protein content. The change of electrophoretic
patterns after heat treatments indicated that soy proteins were dissociated into subunits, some of which coalesced. When the
heating temperature is below their denaturation temperature, the protein fractions cannot completely be denatured even after
heat exposure for extended periods of time.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
9.
Carin A. Helfer Donghai Chen Wayne L. Mattice Barry L. Farmer 《Journal of polymer science. Part A, Polymer chemistry》2005,43(8):886-896
A coarse-grained model has been developed for asymmetrically substituted poly(silylenemethylene)s in which the side chain is a flexible spacer terminated by a biphenyl unit. Each monomer unit is represented by four coarse-grained beads that interact via a Lennard–Jones potential and are subject to the first- and second-order interactions deduced from the atomistically detailed model. Metropolis Monte Carlo simulations were performed for isolated syndiotactic, isotactic, and atactic chains. Snapshots from the equilibrated coarse-grained chain on the discrete space of a high coordination lattice were reverse-mapped to atomistically detailed structures in continuous space. At 373 K, the chains were disordered independent of the stereochemical composition. The occupancy of bond pairs depended on the stereochemical composition, with the trans-gauche (tg) sequence being favored by the isotactic chain. When the simulation was performed with the backbone constrained to specific periodic structures, the g helix was the lowest energy structure for either the atactic or isotactic chains. For the syndiotactic chain, the g and gt helices were favored. The appearance of the g helix as the favored periodic structure of the isolated chain was consistent with the chain conformation reported previously for the smectic phase of this polymer in the bulk state. The g helix was disrupted when the backbone was allowed to access nonhelical conformations, even though these conformations may have been slightly higher in energy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 886–896, 2005 相似文献
10.
Davies CJ Fawcett J Shutt R Solan GA 《Dalton transactions (Cambridge, England : 2003)》2005,(15):2630-2640
Alkylation of (ArNHCH2CH2){(2-C5H4N)CH2}NH with RX [RX = MeI, 4-CH2=CH(C6H4)CH2Cl) and (2-C5H5N)CH2Cl] in the presence of base has allowed access to the sterically demanding multidentate nitrogen donor ligands, {(2,4,6-Me3C6H2)NHCH2CH2}{(2-C5H4N)CH2}NMe (L1), {(2,6-Me3C6H3)NHCH2CH2}{(2-C5H4N)CH2}NCH2(C6H4)-4-CH=CH2 (L2) and (ArNHCH2CH2){(2-C5H4N)CH2}2N (Ar = 2,4-Me2C6H3 L3a, 2,6-Me2C6H3 L3b) in moderate yield. L3 can also be prepared in higher yield by the reaction of (NH2CH2CH2){(2-C5H4N)CH2}2N with the corresponding aryl bromide in the presence of base and a palladium(0) catalyst. Treatment of L1 or L2 with MCl2 [MCl2 = CoCl2.6H2O or FeCl2(THF)1.5] in THF affords the high spin complexes [(L1)MCl2](M = Co 1a, Fe 1b) and [(L2)MCl2](M = Co 2a, Fe 2b) in good yield, respectively; the molecular structure of reveals a five-coordinate metal centre with bound in a facial fashion. The six-coordinate complexes, [(L3a)MCl2](M = Co 3a, Fe 3b, Mn 3c) are accessible on treatment of tripodal L3a with MCl2. In contrast, the reaction with the more sterically encumbered leads to the pseudo-five-coordinate species [(L3b)MCl2](M = Co 4a, Fe 4b) and, in the case of manganese, dimeric [(L3b)MnCl(mu-Cl)]2 (4c); in 4a and 4b the aryl-substituted amine arm forms a partial interaction with the metal centre while in 4c the arm is pendant. The single crystal X-ray structures of , 1a, 3b.MeCN, 3c.MeCN, 4b.MeCN and 4c are described as are the solution state properties of 3b and 4b. 相似文献
11.
12.
Synthesis and crystal structures of two new compounds, K2[CrCl5(H2O)] ( I ) and (NH4)2[CrCl5(H2O)] ( II ) are reported. Both compounds were prepared from chromium(VI) salts by two different methods and reaction pathways of these syntheses are suggested. The crystal structures of these two aquapentachlorochromates(III) have been determined from three dimensional X‐ray data collected at low temperature, 173 K. The two structures are isomorphous and their unit cell dimensions are quite similar. They are orthorhombic, space groups Pnma, with Z = 4. Both structures are composed of [CrCl5(H2O)]2? units held together by the counterion framework. The coordination around the chromium ion deviates from a regular octahedron due to the shorter equatorial chromium‐oxygen bond. 相似文献
13.
A new copper(II) acetate, [Na(2)Cu(CH(3)COO)(4)(H(2)O)].H(2)O (1), has been crystallized from an aqueous solution containing sodium acetate and copper(II) acetate monohydrate in a 4:1 ratio and the structure determined by X-ray crystallography. 1 crystallizes in the monoclinic space group P2(1)/c, with a = 16.638(3) A, b = 11.781(2) A, c = 15.668(3) A, beta = 90.11(3) degrees, V = 3071.0(11) A(3), and Z = 4. In the asymmetric unit, sodium ions bridge two crystallographically unique square planar [Cu(CH(3)COO)(4)](2-) units to their symmetry-generated neighbors to form corrugated 2D sheets of Na(2)Cu(CH(3)COO)(4), which are held together by H-bonding interactions involving the waters of crystallization. In contrast, the structures of known sodium copper acetates are better described as 3D frameworks. The metal centers are bridged by a number of acetates in novel coordination modes. The square planar Cu(II) geometry generated by oxygen atoms from four different acetates is an unexpected feature given the weak ligand field provided by the acetate ligands. 相似文献
14.
A new nickel(Ⅱ) coordination complex [Ni(2,2'-bipy)2(ClC6H4COO)(H2O)](ClO4) was synthesized by self-assembly reaction of m-chlorobenzoic acid, 2,2'-bipy and Ni(ClO4)2(6H2O. The crystal of the title compound belongs to monoclinic system, space group P21/n with a = 0.77764(14), b = 2.6572(5), c = 1.3637(2) nm, β = 96.456(3)°, V = 2.8000(9) nm3, Dc = 1.528 g/cm3, Z = 4, Mr = 644.10, μ(MoKα) = 0.937 mm-1, F(000) =1320, R = 0.0549 and wR = 0.1164. Structure analysis shows that the nickel(Ⅱ) ion is coordinated with four nitrogen atoms from two bipys as well as two oxygen atoms from m-chlorobenzoic acid and water, respectively, giving a distorted octahedral coordination geometry. The cyclic voltametric behavior of the complex is also presented. 相似文献
15.
The trifunctional ligand 2,6-[(C6H5)2P(O)CH2]2 C5H3NO (1), in a mixed EtOH/MeOH solvent system, when combined with an aqueous nitric acid solution of Pu(IV), produces a 2:1 coordination complex, [Pu(1)2(NO3)2](NO3)2. A single crystal of [Pu(NO3)2(2,6-[(C6H5)2P(O)CH2]2C5H3NO)2](NO3)2x1.5H2Ox0.5MeOH was characterized by X-ray diffraction analysis. The crystal is monoclinic, space group P2(1)/n, with a = 19.1011(9) A, b = 18.2873(9) A, c = 21.507(1) A, alpha = gamma = 90 degrees, beta = 108.64(1) degrees, and Z = 4. Two neutral ligands (1) are bonded to the Pu(IV) ion in a tridentate fashion. Two nitrate ions also occupy inner sphere coordination positions, while two additional NO3- ions reside in the outer sphere. Comparison of the solution optical absorbance and solid diffuse reflectance spectra shows the same Pu(IV) chromophore exists in both solid and solution states. 相似文献
16.
标题配合物是由三齿配体N, N-二(2-苯并咪唑亚甲基)胺(IDB)、Ni(ClO4)2·6H2O与水杨酸钠在乙醇溶液中反应得到的紫色晶体。用X-射线衍射测定了其单晶结构。结果表明,该晶体属三斜晶系,P 空间群,化学式:C41H43ClN10NiO9,Mr = 914.01,a = 11.010(2),b = 13.800(3),c = 15.550(3) 牛 = 100.75(3),?= 102.97(3), = 107.56(3)? V = 2111.3(7) ?,Z = 2,F(000) = 952,Dc = 1.438 g/cm3,(MoK) = 0.591 mm-1,8215个独立可观测点(I>2(I))。最终偏离因子R(I>2(I)):R = 0.0591, wR = 0.1325;R(全部数据): R = 0.1302,wR = 0.1572。结构分析表明,镍(Ⅱ)分别与2个IDB配体中的苯并咪唑的4个氮和胺基的2个氮配位形成畸变的八面体构型。 相似文献
17.
Haitao X Nengwu Z Ruyi Y Yonggang W Jianmin L 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2000,(11):2203-2206
The electronic absorption spectrum (diffuse reflection spectrum) of the crystal of [Cu6(bpy)10([mu-CO3)2(mu-OH)2](ClO4)6 . 4H2O has been measured. The experimental results are discussed quantitatively with ligand field theory and the radial wave function of non-free copper(II), and calculation values agree well with the experimental results. The d-d absorption spectrum of a novel hexanuclear copper(II) complex was explained satisfactorily. Especially, complexity of multinuclear crystal structures determined that of spectral behaviors. It provides significant to grope spectral nature from coordination structures. 相似文献
18.
1-甲基-1-丙基-3-丁烯基环戊二烯基钆配合物的合成和晶体 结构分析 总被引:2,自引:0,他引:2
用X-射线晶体结构衍射法测定了[C~5H~4C(CH~3)(C~3H~7)CH~2CH=CH~2]Gd(OH)Cl.2MgCl~2.4THF的晶体结构。它属三斜晶系,空间群为P1,a=1.2757(3),b=1.3571(3),c=1.3725(3)nm,α=69.22(3),β=84.91(3),γ=63.48(3)ⅲ,V=1.929(1)nm^3,Mr=862.75,Dx=1.423g/cm^3,μ=2.0832mm^-^1,F(000)=848,Z=2,R=0.096,ωR=0.113(I≥3σ(I))。分子中Gd原子的配位数为8,形成一个严重扭曲的八面体结构;两个Mg原子的配位情况相似,它们的配位数都是6,构成两个扭曲的八面体。这三个八面体通过三个共用平面联接。 相似文献
19.
1 INTRODUCTION Manganese has been implicated as an essential part of the active center in various manganese enzymes. Various nuclearities have been observed from mononuclear atom in superoxide dismutase [1] to the tetranuclear atom of oxygen evolution in photosystem II[2]. The manganese active centers in biological systems are surrounded by O and N coordination sphere[3, 4]. Synthetic efforts have produced a great variety of Mn clusters with varying nuclearity and oxidation states. Si… 相似文献
20.
The synthesis of nickel supramolecular compound with hexamethylenetetramine and fumarate ligands is reported. The compound [Ni(H2O)6(fum)]·2(hmt)·4H2O (1) (fum=fumarate; hmt=hexamethylenetetramine) were characterized by elemental analysis, crystal structure, IR. Compound 1 crystallizes in the triclinic system, space group P1, and with Z=1. Cell parameters: a=0. 934 6(1), b=0.933 8(1), c=0.938 8(2) nm, α=79.46(1)°, β=77.84(1)°, γ=61.29 6(7)°. Every metal ion has a octahedral coordination geometry formed by six oxygen atoms from six water molecules, and the relative independent components [Ni(H2O)6]2+, fumarate anions, hmt and H2O molecules are linked together by two kinds of hydrogen bonds (O-H…O, and O-H…N) to form a three-dimensional structure. CCDC: 256355. 相似文献