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31.
Minelli M Hoang ML Kraus M Kucera G Loertscher J Reynolds M Timm N Chiang MY Powell D 《Inorganic chemistry》2002,41(23):5954-5960
Anilines with alkyl substituents on the phenyl ring (ArNH2 = 2,4,6-trimethylaniline; 2,3-, 2,4-, 2,6-, and 3,4-dimethylaniline; and 2,6-diisopropylaniline) react with MoO(X)2(dtc)2 (X = Cl or Br; dtc = diethyldithiocarbamate) in methanol in the presence of 2 equiv of triethylamine to form ionic imido complexes of the type [MoNAr(dtc)3]2[Mo6O19] or MoNAr(dtc)3]4[Mo8O26]. The same reaction in THF with butyllithium as base yields imido complexes of the type MoNAr(X)2(dtc)2. The structures of three ionic, five chloro, and two bromo complexes have been determined by X-ray crystallography. In all complexes, the molybenum center is a distorted pentagonal bipyramid. While the structures are similar, the angles of the imido linkages differ. The effect of the substituents on the phenyl ring of the imido ligand on the 95Mo NMR chemical shifts was determined. The Mo nucleus becomes more deshielded with the substituents in the following order: 3,4-Me2 < 2,3-Me2 < 2,4-Me2 < 2,6-Me2 < 2,4,6-Me3 < 2,6 isopropyl. Complexes with more deshielded 95Mo centers tend to have angles of the imido linkage that are closer to 180 degrees. 相似文献
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33.
Benjamin E. Kucera Robert E. Jilek William W. Brennessel John E. Ellis 《Acta Crystallographica. Section C, Structural Chemistry》2014,70(8):749-753
Reduction of VCl3(THF)3 (THF is tetrahydrofuran) and NbCl4(THF)2 by alkali metal pyrene radical anion salts in THF affords the paramagnetic sandwich complexes bis[(1,2,3,3a,10a,10b‐η)‐pyrene]vanadium(0), [V(C16H10)2], and bis[(1,2,3,3a,10a,10b‐η)‐pyrene]niobium(0), [Nb(C16H10)2]. Treatment of tris(naphthalene)titanate(2−) with pyrene provides the isoelectronic titanium species, isolated as an (18‐crown‐6)potassium salt, namely catena‐poly[[(18‐crown‐6)potassium]‐μ‐[(1,2‐η:1,2,3,3a,10a,10b‐η)‐pyrene]‐titanate(−I)‐μ‐[(1,2,3,3a,10a,10b‐η:6,7‐η)‐pyrene]], {[K(C12H24O6)][Ti(C16H10)2]}n. The first two compounds have very similar packing, with neighboring molecules arranged orthogonally to one another, such that aromatic donor–acceptor interactions are likely responsible for the specific arrangement. The asymmetric unit contains a half‐occupancy metal center η6‐coordinated to one pyrene ligand, with the full M(pyrene)2 molecule generated by a crystallographic inversion center. In the titanium compound, the cations and anions are in alternating contact throughout the crystal structure, in one‐dimensional chains along the [101] direction. As in the other two compounds, the asymmetric unit contains a half‐occupancy Ti atom η6‐coordinated to one pyrene ligand. Additionally, the asymmetric unit contains one half of an (18‐crown‐6)potassium cation, located on a crystallographic inversion center coincident with the K atom. The full formula units are generated by those inversion centers. In all three structures, the pyrene ligands are eclipsed and sandwich the metals in one of two inversion‐related sites. These species are of interest as the first isolable homoleptic pyrene transition metal complexes to be described in the scientific literature. 相似文献
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Pawlak PL Panda M Loloee R Kucera BE Costes JP Tuchagues JP Chavez FA 《Dalton transactions (Cambridge, England : 2003)》2011,40(12):2926-2931
Two new binuclear metal complexes supported by 1,4,8-triazacycloundecane (tacud) are reported. [Fe(2)(tacud)(2)(μ-Cl)(2)Cl(2)] (1) and [Mn(2)(tacud)(2)(μ-Cl)(2)Cl(2)] (2) are isomorphs consisting of bis(μ-chloro) bridged metal centers along with terminal chloro groups and tacud ligands. Both compounds 1 and 2 crystallize in the P1 space group. For 1, a = 7.7321(12) ?, b = 7.8896(12) ?, c = 11.4945(17) ?, α = 107.832(2)°, β = 107.827(2)°, γ = 92.642(2)°, V = 627.85(17) ?(3) and Z = 1. For 2, a = 7.7607(12) ?, b = 7.9068(12) ?, c = 11.6111(18) ?, α = 108.201(2)°, β = 108.041(2)°, γ = 92.118(3)°, V = 636.47(17) ?(3) and Z = 1. Variable-temperature and variable-field magnetic susceptibility studies on 1 indicate the presence of weak ferromagnetic interactions between the high-spin iron(ii) centers in the dimer (J = + 1.6 cm(-1)) and the crystalline field anisotropy of the ferrous ion (D = - 2.8, E = - 0.1 cm(-1)). Variable temperature magnetic susceptometry studies on 2 indicate that weak antiferromagnetic coupling exists between the manganese(ii) centers (J = - 1.8 cm(-1)). Compounds 1 and 2 retain their dinuclearity in weakly coordinating or low polarity solvents, while both become mononuclear in solvents such as methanol. 相似文献
37.
Cahlíková L Benesová N Macáková K Kucera R Hrstka V Klimes J Jahodár L Opletal L 《Natural product communications》2012,7(5):571-574
Alkaloid extracts of four Amaryllidaceae species were studied with respect to their acetylcholinesterase and butyrylcholinesterase inhibitory activity and alkaloid patterns. Twenty-one alkaloids were determined by GC/MS, and seventeen of them identified from their mass spectra and retention times. The GC/MS analysis of the alkaloid extract of Nerine filamentosa is the first phytochemical investigation of this species. Promising erythrocytic acetylcholinesterase inhibitory activity was demonstrated by the alkaloid extracts of Narcissus poeticus var recurvus, Nerine filifolia and N. filamentosa (IC(50,HuAChE) = 6.0 +/- 0.1 microg/mL; IC(50,HuAChE) = 18.5 +/- 0.8 microg/mL, IC(50,HuAChE) = 21.6 +/- 1.1 microg/mL). The most potent inhibitory activity against serum butyrylcholinesterase was shown by extracts of Sternbergia lutea and Nerinefilamentosa (IC(50,HuBuChE) = 3.7 +/- 0.1 microg/mL; IC(50.HuBuChE) = 13.0 +/- 0.7 microg/mL). 相似文献
38.
Jan Tous Karel Blazek Miroslav Kucera Martin Nikl Jiri A. Mares 《Radiation measurements》2012,47(4):311-314
Very thin scintillator imaging plates have recently become of great interest. In high resolution X-ray radiography, very thin scintillator layers of about 5–20 μm are used to achieve 2D-spatial resolutions below 1 μm. Thin screens can be prepared by mechanical polishing from single crystals or by epitaxial growth on single-crystal substrates using the Liquid Phase Epitaxy technique (LPE). Other types of screens (e.g. deposited powder) do no reach required spatial resolutions. This work compares LPE-grown YAG and LuAG scintillator films doped with different rare earth ions (Cerium, Terbium and Europium). Two different fluxes were used in the LPE growth procedure. These LPE films are compared to YAG:Ce and LuAG:Ce screens made from bulk single crystals. Relative light yield was detected by a highly sensitive CCD camera. Scintillator screens were excited by a micro-focus X-ray source and the generated light was gathered by the CCD camera’s optical system. Scintillator 2D-homogeneity is examined in an X-ray imaging setup also using the CCD camera. 相似文献
39.
Jiri A. Mares Petr Prusa Martin Nikl Karel Nitsch Alena Beitlerova Miroslav Kucera Martin Hanus Yurij Zorenko 《Radiation measurements》2010,45(3-6):369-371
Scintillating properties of Ce3+-doped (Lu,Y) aluminum garnet single crystalline films (SCF) were investigated. Thin SCF films of thickness between 1 and 30 μm were grown by a liquid phase epitaxy (LPE) method in various fluxes. The α-particle excitation (mainly 5.4857 MeV line of 241Am) of pulse height spectra is used to measure scintillation response of SCF, especially peak of those α-rays which are totally absorbed in the films. Detailed studies and evaluation of scintillation measurements of large sets of Ce3+-doped SCF (Lu,Y) aluminum garnets showed that at present time (i) YAG:Ce SCF have comparable scintillation properties as YAG:Ce single crystals, especially their Nphels photoelectron yields are the same while (ii) scintillation properties of LuAG:Ce SCF do not reach those of LuAG:Ce single crystal. 相似文献
40.
Aramice Y. S. Malkhasian Borislava Nikolovski Benjamin E. Kucera Reza Loloee Ferman A. Chavez Prof. Dr. 《无机化学与普通化学杂志》2007,633(7):1000-1005
FeIIL2(OTf)2 ( 1 ) and MnIIL2(OTf)2 ( 2 ) (L = tris(1‐ethyl‐4‐methylimidazolyl‐κN)phosphine; OTf= trifluoromethanesulfonate) were synthesized and their X‐ray structures were determined. Both complexes possess distorted octahedral geometry with high spin electron configuration at ambient temperature. Compound 1 exhibits a quasi‐reversible wave with E1/2 of 0.745 V versus Ag/AgNO3. Variable temperature magnetic measurements indicate that no spin‐crossover phenomenon for 1 is observed between 2.5 and 300 K. In addition, a plot of 1/χM versus T(K) is linear with a Curie constant of 3.48 emu mol?1 K. 相似文献