排序方式: 共有75条查询结果,搜索用时 156 毫秒
71.
72.
Li P Ahrens B Bond AD Davies JE Koentjoro OF Raithby PR Teat SJ 《Dalton transactions (Cambridge, England : 2003)》2008,(12):1635-1646
A series of novel digold complexes incorporating ethynyl pyridine derivatives as a spacer unit, [(R(3)P)Au(C[triple bond]C)X(C[triple bond]C)Au(PR(3))] (R = Ph, X = 2,5-pyridine (1); R = Cy (cyclohexane), X = 2,5-pyridine (2); R = Ph, X = 2,6-pyridine (3); R = Ph, X = 2,5'-bipyridine (4); R = Ph, X = 2,6'-bipyridine (5)), has been synthesised. All the complexes have been characterised spectroscopically and the structures determined by single-crystal X-ray crystallography. The central (C[triple bond]C)(X)(C[triple bond]C) unit is essentially linear for complexes 1, 2 and 4 and kinked for complexes 3 and 5, but only in 1, with the shortest spacer group and the less bulky phosphine ligand, is there evidence of d(10)...d(10) Au...Au interactions (Au-Au 3.351(2) A). The solution UV/visible absorption and emission spectra for all the complexes are similar to those of the free ligands suggesting that the spectra are dominated by pi-pi* ligand-centred transitions and this is confirmed by DFT calculations. 相似文献
73.
Burhenne J Halama B Maurer M Riedel KD Hohmann N Mikus G Haefeli WE 《Analytical and bioanalytical chemistry》2012,402(7):2439-2450
The benzodiazepine midazolam is a probe drug used to phenotype cytochrome P450 3A activity. In this situation, effective sedative
concentrations are neither needed nor desired, and in fact the use of very low doses is advantageous. We therefore developed
and validated an assay for the femtomolar quantification of midazolam and 1′-hydroxymidazolam in human plasma. Plasma (0.25 mL)
and 96-well-based solid-phase extraction were used for sample preparation. Extraction recoveries ranged between 75 and 92%
for both analytes. Extracts were chromatographed within 2 min on a Waters BEH C18 1.7 μm UPLC? column with a fast gradient
consisting of formic acid, ammonia, and acetonitrile. Midazolam and 1′-hydroxymidazolam were quantified using deuterium- and
13C-labeled internal standards and positive electrospray tandem mass spectrometry in the multiple reaction monitoring mode,
which yielded lower limits of quantification of 50 fg/mL (154 fmol/L) and 250 fg/mL (733 fmol/L) and a corresponding precision
of <20%. The calibrated concentration ranges were linear for midazolam (0.05–250 pg/mL) and 1′-hydroxymidazolam (0.25–125 pg/mL),
with correlation coefficients of >0.99. Within-batch and batch-to-batch precision in the calibrated ranges for both analytes
were <14% and <12%. No ion suppression was detectable, and plasma matrix effects were minimized to <15% (<25%) for midazolam
(1′-hydroxymidazolam). The assay was successfully applied to assess the kinetics of midazolam in two human volunteers after
the administration of single oral microgram doses (1–100 μg). This ultrasensitive assay allowed us to quantify the kinetics
of midazolam and 1′-hydroxymidazolam for at least 10 h, even after the administration of only 1 μg of midazolam. 相似文献
74.
Hydroxy‐telechelic poly(methyl methacrylate)s of molecular weights below 5000 were obtained by atom transfer radical polymerization (ATRP) of methyl methacrylate followed by end‐capping with allyl alcohol via atom transfer radical addition (ATRA). As initiators for the ATRP, monofunctional initiators with an additional hydroxy group in the molecule or bifunctional initiators were employed. The successful synthesis of the hydroxy‐telechelic PMMA was proved by determination of their molecular weight using MALDI‐TOF‐MS. The efficiency of the end‐capping reaction was determined by 1H NMR spectroscopy using the allyl N‐(4‐tolyl)carbamate as end‐capping agent. Block copolymers comprising a poly(ethylene oxide) (PEO) block and a poly(methyl methacrylate) (PMMA) block were prepared by ATRP using a macroinitiator on the PEO basis. The dormant species of the macroinitiator consists of the phenyl chloroacetate moiety which shows a high rate of initiation. The successful synthesis of the poly(ethylene oxide)‐block‐poly(methyl methacrylate) was proved by 1H NMR spectroscopy; the ratios of EO/MMA repeating units in the feed and the copolymer were nearly equal. 相似文献
75.
Michael Osterhold Birte Bannert Walter Schubert Thomas Brock 《Macromolecular Symposia》2002,187(1):823-834
The study examines the effect of weathering on mechanical and chemical properties of two 2K (twopack, with and without light stabilisation additives) and one 1K (onepack) clearcoats, concentrating on scratch and mar resistance and acid etch resistance. The clearcoats were investigated before and in the course of accelerated weathering. For determining the mar resistance two different instruments were used: - AMTEC laboratory car wash equipment (rotating wet brush) - Crockmeter Explanations for the changes in clearcoat properties caused by weathering are given by Dynamic-Mechanical Analysis, FT-IR-Spectroscopy, Universal-hardness and surface tension measurements. The clearcoat systems investigated show a clear deterioration of their properties after short periods of accelerated weathering. This effect is more expressed for the clearcoat samples without light stabilizers. 相似文献