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排序方式: 共有163条查询结果,搜索用时 15 毫秒
21.
Paloma Paredes 《Journal of organometallic chemistry》2008,693(24):3681-3687
The treatment of the complex [Ir(η2-C2H4)2(L)][PF6] (L = κ3-N,N,N-(S,S)-iPr-pybox) with acetic acid (1:1 molar ratio) at −10 °C affords the complex [Ir(C2H5)(κ2-O,O-O2CCH3)(L)][PF6] (1). The dinuclear iridium(III) complex [Ir2(μ-Cl)2(C2H5)2(L)2][PF6]2 (2) is stereoselectively obtained by spontaneous intramolecular insertion of ethylene into the iridium-hydride bond of the mononuclear complex [IrClH(η2-C2H4)(L)][PF6]. The single bridging chloride dinuclear derivative [Ir2(μ-Cl)(C2H5)2Cl2(L)2][PF6] (3) is prepared by reaction of 2 with one equivalent of NaCl. The intramolecular insertion reaction of methyl and ethyl propiolate into the Ir-H bond of the complex [IrClH(MeCN)(L)][PF6] gives stereoselectively the dinuclear complexes [Ir2(μ-Cl)2(HCCHCO2R)2(L)2][PF6]2 (R = Me (4), Et (5)). The reaction of the complexes 4, 5 with one equivalent of NaCl or with an excess of sodium acetate yields the dinuclear [Ir2(μ-Cl)(HCCHCO2R)2Cl2(L)2][PF6] (R = Me (6), Et (7)) or the mononuclear [IrCl(HCCHCO2Et)(κ1-O-O2CMe)(L)] (8) complexes, respectively. The structure of the dinuclear complex 3 · CH2Cl2 has been determined by an X-ray monocrystal study. 相似文献
22.
The present work describes a new analytical method for direct immunoaffinity column clean-up of ochratoxin A (OTA) in milk samples followed by determination of the toxin using high-performance liquid chromatography with fluorescence detection (HPLC-FD). Two different immunoaffinity cartridges (IAC) were investigated, and Ochraprep columns were chosen because they showed the best results. An average recovery of 89.8% and a mean RSD of 5.8% for artificially contaminated cow's milk in the range of 5-100 ng/L were attained. The calculated limit of detection (LOD) and limit of quantitation (LOQ) were as low as 0.5 and 5 ng/L, respectively. This new easy and fast method avoids a previous liquid-liquid extraction step and therefore the use of toxic chlorinated solvents. Chromatograms of the final extracts were clean and OTA could be easily detected at a retention time of 8.4 min without interferences. To assess the presence of the toxin in cow's milk eight samples of skimmed and four samples of whole milk were analysed and OTA was not detected over the established detection limit. 相似文献
23.
This study presents a simple method for measuring long-range heteronuclear coupling constants between protons and proton-bearing carbons. The approach involves recording two conventional 1D-TOCSY experiments in which the offset of the selective proton pulse is set on the low- and high-frequency 13C satellites of an isolated proton signal, Hi. Long-range heteronuclear coupling values between the 13Ci bonded to Hi and the protons Hj,k...n that belong to the same spin system were easily determined from the relative displacement of the relayed Hj,k...n signals in the satellite-selective TOCSY spectra. The sense of the displacement indicated the sign of the coupling constants. 相似文献
24.
López JC Bernal-Albert P Uriel C Valverde S Gómez AM 《The Journal of organic chemistry》2007,72(26):10268-10271
The combination of bis(pyridinium)iodonium (I) tetrafluoroborate (IPy2BF4), and hydrogen fluoride pyridine (HF-py) forms an iodine monofluoride (IF) synthetic equivalent that can be used in the preparation of partially unprotected glycosyl fluorides from partially unprotected n-pentenyl glycosides and thioglycosides, thus avoiding the need for the protection/deprotection steps normally required in that transformation. 相似文献
25.
Taboada L Prieto L Vidal P Espinosa JF Erickson JA 《Journal of combinatorial chemistry》2007,9(5):748-755
Here we describe a multistep solid-phase synthetic approach for the addition of amino acid residues to both the C- and N-termini of a phenylstatine core, yielding a library aimed at the development of structure-activity relationships in the S2 and S2' regions of the aspartyl proteases. Optimization of the synthetic strategy was performed on the basis of the in situ analysis of the compounds bound to the solid support through high-resolution magic angle spinning NMR Spectroscopy (HR-MAS NMR). 相似文献
26.
Néstor Armesto Carlos Pajares Paloma Quiroga-Arias 《The European Physical Journal C - Particles and Fields》2009,61(4):779-784
We study the modification of the multiplicity distributions in MLLA due to the presence of a QCD medium. The medium is introduced
through a multiplicative constant (f
med) in the soft infrared parts of the kernels of the QCD evolution equations. Using the asymptotic ansatz for mean multiplicities
of the quark and gluons, 〈n
G〉=e
γ
y
and 〈n
Q〉=r
−1e
γ
y
, respectively, we study two cases: fixed γ as previously considered in the literature, and fixed α
s
. We find opposite behaviors of the dispersion of the multiplicity distributions with increasing f
med in both cases. For fixed γ the dispersion decreases, while for fixed α
s
it increases. 相似文献
27.
28.
Rafael Cuesta Paloma Arranz‐Mascars John N. Low Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(8):918-921
In the title compound, [Na(C5H5N4O3)]·2H2O, each Na cation is linked to three C5H4N4O3? anions and two water molecules, forming approximately octahedral NaNO5 units; the cations and the anions form molecular ladders, and each ladder is linked to four neighbouring ladders by O—H?O and O—H?N hydrogen bonds. 相似文献
29.
Synthesis, Crystal Structure and Spectroscopic Characterization of [Au12(PPh)2(P2Ph2)2(dppm)4Cl2]Cl2 The reaction of [(AuCl)2dppm] (dppm = Ph2PCH2PPh2) with P(Ph)(SiMe3)2 in CHCl3 results in the formation of [Au12(PPh)2(P2Ph2)2(dppm)4Cl2]Cl2 ( 1 ), the crystal structure of which was determined by single crystal X‐ray analysis (space group P21/c, a = 1425.3(3) pm, b = 2803.7(6) pm, c = 2255.0(5) pm, β = 95.00(3)°, V = 8977(3)·106 pm3, Z = 2). The dication in 1 consists of two Au6P3 units built by highly distorted Au3P and Au2P2 heterotetrahedra, connected via four bidentate phosphine ligands. Additionally, the compound was characterized by IR‐, UV‐ and NMR spectroscopy. The 31P{1H} NMR spectrum is discussed in detail. 相似文献
30.
Dulce?Paloma?del J.?Gutiérrez-Hijar Fausto?Becerra J.?E.?Puig J.?Félix?Armando?Soltero-Martínez María?Belén?Sierra Pablo?C.?SchulzEmail author 《Colloid and polymer science》2004,283(1):74-83
The aggregation of two polymerisable surfactants dodecylethylmethacrylatedimethylammonium bromide (C12PS) and hexadecylethylmethacrylatedimethylammonium bromide (C16PS) was studied with a battery of methods. Both surfactants form premicelles at low concentration, and show a critical micelle concentration and a transition between spherical and rod-like micelles. The micelle ionization degree and the adsorption at the air/solution interface were also studied. Results are interpreted on the basis of the conformation of the polar head group. 相似文献