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41.
Ternary Lithium Rare Earth Nitrates with Lonesome Nitrate Ions: Li3[M(NO3)5](NO3) (M = Gd? Lu, Y). The Crystal Structure of Li3Er(NO3)6 Single crystals of the ternary nitrate Li3Er(NO3)6 are obtained from a solution of “Er(NO3)3” in the melt of LiNO3. In Li3Er(NO3)6 (monoclinic, P21/n, Z = 4; a = 776.0(1); b = 748.86(8); c = 2 396(1) pm; β = 90.76(3)°; R1 = 0.0490; wR2 = 0.0792), Er3+ is surrounded by five bidentate nitrate ligands yielding the anionic units [Er(NO3)5]2?. These are arranged in the direction of the 21 screw axis. Two lonesome NO3? ions are in the middle of such a “helix” and are connected by Li+ with the anions [Er(NO3)5]2?. The helices are moved against each other by about half of the lattice constant a and are connected by further Li+ ions. 相似文献
42.
D. Rosmann K. -W. Klinkhammer A. Schmidt 《Monatshefte für Chemie / Chemical Monthly》1996,127(5):461-468
Zusammenfassung Arsen-tris(2,2-dimethylpropionat) (1) kristallisiert monoklin in der Raumgruppe P21/n mita=926.2,b=2158.6,c=983.7 pm, =94.92° undZ=4. As hat gegenüber O die Koordinationszahl 3+3. Antimontripropionat (2) kristallisiert monoklin in der Raumgruppe P21/c mita=930.2,b=863.0,c=1575.2 pm, =90.27 undZ=4. Die Moleküle sind intermolekular zu Ketten verknüpft, wodurch Sb die Koordinationszahl 3+3 (+3) erreicht.
Structure of arsen(III) and antimony(III) carboxylates
Summary Arsen-tris(2,2-dimethylpropionate) (1) crystallizes monoclinic in the space group P21/n witha=926.2,b=2158.6,c=983.7 pm, =94.92°, andZ=4. As has a coordination number of 3+3. Antimony tripropionate (2) crystallizes monoclinic in the space group P21/c witha=930.2,b=863.0,c=1575.2 pm, =90.27, andZ=4. The molecules are bridged to chains; therefore, Sb reaches the coordination number 3+3 (+3).相似文献
43.
Edith Gößnitzer Ales Krbavcic Winfried Wendelin Marija Krbavcic 《Monatshefte für Chemie / Chemical Monthly》2002,133(9):1177-1185
Summary. Novel N-(3-oxobutyl)-hydroxy- and acetoxypyrido[2,3-d]pyridazinones were synthesized and tested in vivo for their sedative and anticonvulsant activity. The Michael-type reaction of quinolinic acid hydrazide and methyl vinyl ketone afforded a mixture of two isomers, 5-hydroxy-N
7-(3-oxobutyl)-pyrido[2,3-d]pyridazin-8(7H)-one and 8-hydroxy-N
6-(3-oxobutyl)-pyrido[2,3,-d]pyridazin-5-(6H)-one, in a ratio of 2:1 which were separated by crystallization. Subsequent acetylation of both isomers yielded the corresponding
5- and 8-acetoxy compounds. The structures of the compounds were proven and completely assigned on the basis of 1H, 13C, 15N NMR, and 1D NOE difference spectra as well as 2D C,H-correlation experiments. Preliminary pharmacological tests showed low
acute toxicity with a LD
50 > 1000 mg/kg in the mouse and sedative activity for the title compounds. 5-Acetoxy-N
7- (3-oxobutyl)-pyrido[2,3-d]pyridazin-8(7H)-one displayed a borderline anticonvulsant activity in the metrazole test model.
Corresponding author. E-mail: edith.goessnitzer@uni-graz.at
Received March 20, 2002; accepted April 3, 2002 相似文献
44.
45.
Titanosilicates with complete or partial substitution of Ge or Nb in the framework and having the mineral pharmacosiderite topology were hydrothermally prepared and their ion-exchange properties towards Cs were studied for Ti/Ge/Si, Ti/Si, Nb/Ti/Si and pure Ge phases. The basis for the differences in the ion exchange properties measured as distribution coefficients (Kd) for these materials are detailed via structural characterization using the Rietveld refinement technique on the X-ray powder diffraction data. The differences in affinity towards Cs+ result either from the degree of hydration of the exchanger resulting in different coordination environments or the position of cesium ion in the eight-ring channel. 相似文献
46.
固相氯化法合成氯化聚乙烯的红外光谱研究 总被引:2,自引:0,他引:2
本文研究在不同条件固相氯化聚乙烯(CPE)的红外光谱,探讨了一步和两步氯化合成的CPE的结构差别,着重讨论了两步氯化的CPE结构特点。从观察表征结晶结构和—(CH_2)_n—链段氯分布的特征频率变化表明,低温固相氯化主要发生在无定形区,并且在CPE中形成高氯化和低氯化链段(或未氯化)的嵌段结构。在两步固相氯化时,晶区受到较大程度的破坏,氯化作用已不局限在无定形区,其结晶结构的破坏主要同第二步氯化程度有关,即使CPE氯含量相同,若前后两步氯化程度不同,结构有很大差异。 相似文献
47.
R. Ramanauskas L. Gudavičiūtė A. Kaliničenko R. Juškėnas 《Journal of Solid State Electrochemistry》2005,9(12):900-908
The influence of pulse plating parameters on the surface morphology, grain size, lattice imperfection and corrosion properties
of Zn–Ni alloy has been studied. The coatings were electrodeposited in an alkaline cyanide-free solution. AFM was applied
for surface morphology examination, XRD measurements were carried out for phase composition and texture analysis, electron
probe microanalysis was used for alloy chemical composition studies, while electrochemical techniques were applied for corrosion
performance evaluation. The pulse plated Zn–Ni coatings appeared to consist of the γ-Zn21Ni5 phase and the composition of the alloy depended on the plating parameters. The grain size, lattice imperfection and homogeneity
of grain distribution were established to be the main factors determining corrosion behaviour of the coating.
Presented at the 4th Baltic Conference on Electrochemistry, Greifswald, March 13–16, 2005 相似文献
48.
近年来,实验发现钛酸铅基材料具有负热膨胀性,且其热膨胀程度会受到掺杂元素的影响. 目前所研究的A位掺杂体系中,仅Cd原子掺杂能使钛酸铅负热膨胀性增强. 所以研究A位掺杂钛酸铅,比较Cd原子与其他原子在掺杂钛酸铅时化学键的异同,有助于深刻理解钛酸铅负热膨胀的本质. 本文利用第一性原理,分别优化了Sr、Ba、Cd掺杂钛酸铅的晶格常数,计算了它们的态密度和电荷密度. 结果表明Cd―O键的共价性强于Pb―O键,而Ba―O键和Sr―O键几乎呈离子性,Ba/Sr对Pb的替代削弱了化合物的共价性,降低了自发极化强度. 与实验测量的热膨胀系数对比可以发现,A位原子与氧原子之间的共价性增强,化合物负热膨胀程度升高;若A位原子与氧原子之间的共价性削弱,负热膨胀程度降低. 可见A位原子与氧原子之间的共价性影响了钛酸铅基化合物负热膨胀性. 相似文献
49.
六十年代后期,在Hartree-Fock-Slater法的基础上,提出了Xα法[1].用于原子结构计算的Xα法与HF(Hartree-Fock)法的主要区别在于:用简单的统计平均交换势替代了HF法中计算最为困难的电子交换势,从而在保持较高理论严谨性和计算精确度的同时,大大减少了计算工作量,近年来获得了广泛的应用.我们尝试用经过适当修改的Xα方法,计算原子参数,解决分子结构中的某些问题.用原子参数解决分子问题,历来是化学和物理工作者常用的方法.本工作的意图是引入一个比HF法简单的容易在微机上实现的某种表现原子参数的计算方法,提供… 相似文献
50.
Crystal Structures of the Fluorochloroplatinates(IV) cis-[(C5H5N)2CH2][PtF4Cl2], trans-[(C5H5N)2CH2][PtF4Cl2] · H2O, and [(C5H5N)2CH2][PtF5Cl] The complex ions cis-[PtF4Cl2]2?, trans-[PtF4Cl2]2? and [PtF5Cl]2? have been synthesized by stereoselective ligand exchange reactions utilizing the trans effect and are separated by ion exchange chromatography on diethylaminoethyl cellulose. These anions form stable AB-type salts with the doubly charged cation dipyridiniomethane, [(C5H5N)2CH2]2+. X-ray structure determinations on single crystals of cis-[(C5H5N)2CH2][PtF4Cl2] ( 1 ) (monoclinic, space group P21/n with a = 10.379(10), b = 9.635(2), c = 13.738(2) Å, β = 99.142(10)°, Z = 4), trans-[(C5H5N)2CH2][PtF4Cl2] · H2O ( 2 ) (triclinic, space group P1 with a = 7.757(4), b = 10.059(7), c = 10.408(6) Å, α = 82.49(5), β = 68.92(4), γ = 75.46(4)°, Z = 2) and [(C5H5N)2CH2][PtF5Cl] ( 3 ) (orthorhombic, space group Pnma with a = 10.394(3), b = 13.320(2), c = 9.2694(10) Å, Z = 4), reveal the perfect ordering of the anion sublattice. The stronger trans influence of Cl compared with F is observed in asymmetric axes $ {\rm F}^ \bullet $? Pt? Cl′. The bond lengths Pt? $ {\rm F}^ \bullet $ are 0.026 Å (1.4%) longer and the Pt? Cl′ distances are 0.078 Å (3,3%) shorter in comparison with those of symmetrically coordinated axes. The weakening of the Pt? $ {\rm F}^ \bullet $ bond and the strengthening of the Pt? Cl′ bond is better recognizable from shifts of the stretching vibrations by 8% to lower and by 13% to higher frequencies, respectively. Correspondingly, the valence force constants are found to be 15% lower and 22% higher. The trans influence is observed most distinctly in the 19F-nmr spectra exhibiting the coupling constant 1J($ {\rm F}^ \bullet $Pt) to be 29% smaller than 1J(FPt). 相似文献