Reaction of [Ru3(CO)12] with tri(2-furyl)phosphine, P(C4H3O)3, at 40 °C in the presence of a catalytic amount of Na[Ph2CO] furnishes two triruthenium complexes [Ru3(CO)10{P(C4H3O)3}2] (1) and [Ru3(CO)9{P(C4H3O)3}3] (2) with the ligand coordinated through the phosphorus atom. Treatment of 1 and 2 with Me3NO at 40 °C affords the dinuclear phosphido-bridged complexes [Ru2(CO)6(μ-η1,η2-C4H3O){μ-P(C4H3O)2}] (3) and [Ru2(CO)5(μ-η1,η2-C4H3O){μ-P(C4H3O)2}{P(C4H3O)3}] (4), respectively, that are formed via phosphorus–carbon bond cleavage of a coordinated phosphine followed by coordination of the dissociated furyl moiety to the diruthenium center in a σ,π-alkenyl mode. Reaction of [Ru3(CO)12] with tri(2-furyl)phosphine in refluxing benzene gives, in addition to 3 and 4, low yields of the cyclometallated complex [Ru3(CO)9{μ-η1,η1-P(C4H3O)2(C4H2O)}2] (5). Treatment of 3 with EPh3 (E = P, As, Sb) at room temperature yields the monosubstituted derivatives [Ru2(CO)5(μ-η1,η2-C4H3O){μ-P(C4H3O)2}(EPh3)] (E = P, 8; E = As, 9; E = Sb, 10). Similar reactions of 3 with P(C4H3O)3, P(OMe)3 and ButNC yield 4, [Ru2(CO)5(μ-η1,η2-C4H3O){μ-P(C4H3O)2}{P(OMe)3}] (11) and [Ru2(CO)5(μ-η1,η2-C4H3O){μ-P(C4H3O)2}(NCBut)] (12), respectively. The molecular structures of complexes 3, 4 and 8 have been elucidated by single crystal X-ray diffraction studies. Each complex contains a bridging σ,π-alkenyl group and while in 4 the phosphine is bound to the σ-coordinated metal atom, in 8 it is at the π-bound atom. Protonation of 3 and 4 gives the hydride complexes [(μ-H)Ru2(CO)6(μ-η1,η2-C4H3O){μ-P(C4H3O)2}]+ (6) and [(μ-H)Ru2(CO)5(μ-η1,η2-C4H3O){μ-P(C4H3O)2}{P(C4H3O)3}]+ (7), respectively, while heating 3 with dimethylacetylenedicarboxylate (DMAD) in refluxing toluene gives the cyclotrimerization product, C6(CO2Me)6. 相似文献
A highly porous fiber coating material was prepared and functionalized with 3-amino propyl triethoxysilane (APTES) on hexagonally ordered nanoporous silica (SBA-15). Applicability of this coating was assessed employing a laboratory made solid-phase microextraction (SPME) device and gas chromatography–mass spectrometry for the simultaneous sampling and determination of trace polycyclic aromatic hydrocarbons (PAHs) from aqueous sample solutions. A one at the time optimization strategy was applied to investigate and optimize important extraction parameters such as extraction temperature, extraction time, ionic strength and sonication time. In the optimum conditions, the relative standard deviations for deionized water, spiked with selected PAHs were between 3.3 and 7.7% (n = 3), and detection limits for the studied compounds were 4.2 and 26.1 pg mL−1. No significant change was observed in the extraction efficiency of the new SPME fiber, over 50 extractions. The proposed method was successfully applied to the extraction and determination of PAHs in the waste water samples.
Ultrasound-assisted headspace solid-phase microextraction (UA-HS-SPME) coupled to gas chromatography–mass spectrometry (GC–MS) has been used for analysis of volatile compounds in dry Tagetes minuta L. The highest extraction efficiency was achieved with a 100-μm polydimethylsiloxane (PDMS) fiber. Different experimental conditions, for example, type of fiber coating, sonication time, extraction time and temperature, and desorption time, were investigated. Thirty compounds were identified by use of this UA-HS-SPME–GC–MS method. Comparison of the method with the commonly used hydrodistillation (HD) method showed that the proposed method is simpler, needs much less sample, requires shorter extraction time and lower temperature, has high trapping ability, and extracts more volatile and thermally sensitive compounds. The major components identified by use of the method were e-ocimenone (10.3%), cis-β-ocimene (4.8%), α-terpinolene (8.4%), trans-caryophyllene (19.7%), germacrene-d (10.0%), and camphor (3.6%). 相似文献
A poly(vinyl chloride) (PVC) membrane sensor for holmium ions was fabricated based on N‐[(Z)‐1‐(2‐thienyl)‐ methylidene]‐N‐[4‐(4‐{[(Z)‐1‐(2‐thienyl)methylidene]amino} phenoxy)phenyl] amine (TPA) as a new ion carrier, acetophenon (AP) as plasticizing solvent mediator and sodium tetraphenyl borate (NaTPB) as an anion excluder. The electrode shows a good selectivity towards Ho3+ ions respect to other inorganic cations, including alkali, alkaline earth, transition and heavy metal ions. The constructed sensor displays a Nernstian behavior (19.5±0.3 mV/decade) over the concentration range of 1.0×10−6 to 1.0×10−2 mol·L−1 with the detection limit of the electrode being 4.6×10−7 mol·L−1 and very short response time (ca. 5 s). It has a useful working pH range of 3.2–9.8 for at least 8 weeks. The electrode was successfully applied as an indicator electrode for the potentiometric titration of a Ho3+ solution with EDTA and holmium determination in some alloys. The proposed sensor accuracy was studied by the determination of Ho3+ in mixtures of three different ions. 相似文献
In spite of the extensive attention paid on the development of various DNA detection strategies, very few studies have been reported regarding direct detection of DNA sequence and mutation in dsDNA. Here, we describe the feasibility of detection and discrimination of target DNA sequences and single base mutations (SBM) directly in double‐stranded oligonucleotides and PCR products without the need for denaturation of the target dsDNA samples. This goal was achieved by employing a peptide nucleic acid (PNA) chain, self‐assembled on the gold electrode as a probe, which binds to dsDNA and forms PNA‐dsDNA hybrid. 相似文献
In this study, an oxadiazole multi-wall carbon nanotube-modified glassy carbon electrode (OMWCNT?GCE) was used as a highly sensitive electrochemical sensor for hydrazine determination. The surface charge transfer rate constant, ks, and the charge transfer coefficient, ??, for electron transfer between GCE and electrodeposited oxadiazole were calculated as 19.4?±?0.5?s?1 and 0.51, respectively at pH?=?7.0. The obtained results indicate that hydrazine peak potential at OMWCNT?GCE shifted for 14, 109, and 136?mV to negative values as compared with oxadiazole-modified GCE, MWCNT?GCE, and activated GCE surface, respectively. The electron transfer coefficient, ??, and the heterogeneous rate constant, k??, for the oxidation of hydrazine at OMWCNT?GCE were also determined by cyclic voltammetry measurements. Two linear dynamic ranges of 0.6 to 10.0???M and 10.0 to 400.0???M and detection limit of 0.17???M for hydrazine determination were evaluated using differential pulse voltammetry. In addition, OMWCNT?GCE was shown to be successfully applied to determine hydrazine in various water samples. 相似文献
The amplification of phage-displayed libraries is an essential step in the selection of ligands from these libraries. The amplification of libraries, however, decreases their diversity and limits the number of binding clones that a screen can identify. While this decrease might not be a problem for screens against targets with a single binding site (e.g., proteins), it can severely hinder the identification of useful ligands for targets with multiple binding sites (e.g., cells). This review aims to characterize the loss in the diversity of libraries during amplification. Analysis of the peptide sequences obtained in several hundred screens of peptide libraries shows explicitly that there is a significant decrease in library diversity that occurs during the amplification of phage in bacteria. This loss during amplification is not unique to specific libraries: it is observed in many of the phage display systems we have surveyed. The loss in library diversity originates from competition among phage clones in a common pool of bacteria. Based on growth data from the literature and models of phage growth, we show that this competition originates from growth rate differences of only a few percent for different phage clones. We summarize the findings using a simple two-dimensional "phage phase diagram", which describes how the collapse of libraries, due to panning and amplification, leads to the identification of only a subset of the available ligands. This review also highlights techniques that allow elimination of amplification-induced losses of diversity, and how these techniques can be used to improve phage-display selection and enable the identification of novel ligands. 相似文献
An efficient procedure for the synthesis of N‐alkyl‐2,5‐diaryl‐1,3‐dioxol‐4‐amines 3 via a one‐pot reaction of aromatic aldehydes 2 and alkyl isocyanides 1 at room temperature in good yields is described (Scheme 1, Table). 相似文献