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1.
王晨  黄吉玲 《中国化学》2006,24(10):1397-1401
Two new complexes[η~5-C_5H_4CMe_2-(p-fluorophenyl)]TiCl_3(1)and[μ~5-C_5H_4C(cyclo-C_5H_(10))-(p-fluoro-phenyl)]TiCl_3(2)were synthesized and characterized.Their activities and selectivities for trimerization of ethylenewere investigated.The introduction of fluorine atom greatly weakened the arene coordination,but this disadvanta-geous factor can be eliminated by introduction of a bulky substituent,such as cyclo-C_5H_(10),to the bridging carbonlinked to the Cp ring.The combinative effect of the fluorine substitute and the bridging unit can make complex 2 asa highly active and selective catalyst for ethylene trimerization.Its productivity and selectivity for 1-hexene canreach 1024.0 kg·mol~(-1)·h(-1) and 99.3% respectively.  相似文献   

2.
The effects of several ionic liquids (ILs) as mobile‐phase additives in HPLC with fluorescence and UV–Vis detection for the determination of six heterocyclic aromatic amines were evaluated using two different C18 stationary phases with moderate silanol activity. The studied ILs were 1‐butyl‐3‐methylimidazolium tetrafluoroborate, 1‐hexyl‐3‐methylimidazolium tetrafluoroborate and 1‐methyl‐3‐octylimidazolium tetrafluoroborate. The optical behaviour of heterocyclic aromatic amines in presence of ILs was studied and the silanol‐suppressing potency of ILs was evaluated for the two stationary phases studied. Several chromatographic parameters were evaluated in the presence or absence of ILs, or using triethylamine, the most common mobile‐phase additive. The best results were achieved using 1 mM 1‐butyl‐3‐methylimidazolium tetrafluoroborate as mobile‐phase additive and NovaPak® column. In these conditions and with 18% of ACN in the mobile phase, analytical performance of the chromatographic methods using fluorescence and UV–Vis were evaluated, obtaining good precision in all cases (RSD lower than 6.6%) and low LOD (0.001–0.147 μg/mL with UV–Vis and 0.001–0.006 ng/mL with fluorescence detection).  相似文献   

3.
The usefulness of a C60‐fullerene modified gold (Au) electrode in mediating the oxidation of methionine in the presence of potassium ions electrolyte has been demonstrated. During cyclic voltammetry, an oxidation peak of methionine appearing at +1.0 V vs. Ag/AgCl was observed. The oxidation current of methionine is enhanced by about 2 times using a C60 modified gold electrode. The current enhancement is significantly dependent on pH, temperature and C60 dosage. Calibration plot reveals linearity of up to 0.1 mM with a current sensitivity of close to 50 mA L mol?1 and detection limit of 8.2×10?6 M. The variation of scan rate study shows that the system undergoes diffusion‐controlled process. Diffusion coefficient and rate constant of methionine were determined using hydrodynamic method (rotating disk electrode) with values of 1.11×10?5 cm2 s?1 and 0.0026 cm s?1 respectively for unmodified electrode while the values of diffusion coefficient and rate constant of methionine using C60 modified Au electrode are 5.7×10?6 cm2 s?1 and 0.0021 cm s?1 respectively.  相似文献   

4.
Two new kinds of alanine‐substituted calix[4]arene stationary phases of 5,11,17,23‐p‐tert‐butyl‐25,27‐bis(l ‐alanine‐methylester‐N‐carbonyl‐methoxy)‐26,28‐dihyroxycalix[4]arene‐bonded silica gel stationary phase (BABS4) and 5, 11, 17, 23‐p‐tert‐butyl‐25,26,27,28‐tetra(l ‐alanine‐methylester‐N‐carbonyl‐methoxy)‐calix[4]arene‐bonded silica gel stationary phase (TABS4) were prepared and characterized in the present study. They were compared with each other and investigated in terms of their chromatographic performance by using polycyclic aromatic hydrocarbons, disubstituted benzene isomers, and mono‐substituted benzenes as solute probes. The results indicated that both BABS4 and TABS4 exhibited multiple interactions with analytes. In addition, the commonly used Tanaka characterization protocol for the evaluation of commercially available stationary phases was applied to evaluate the properties of these two new functionalized calixarene stationary phases. The Tanaka test results were compared with Zorbax Eclipse XDB C18 and Kromasil phenyl columns, respectively. BABS4 has stronger hydrogen‐bonding capacity and ion‐exchange capacity than TABS4, and features weaker hydrophobicity and hydrophobic selectivity. Both of them behave similarly in stereoselectivity. Both BABS4 and TABS4 are weaker than C18 and phenyl stationary phases in hydrophobicity and hydrophobic selectivity.  相似文献   

5.
Singlet cyclo‐1,3‐dipnicta‐2,4‐diazane‐1,3‐diyls of the type [E(μ‐NTer)2E] ( 2 , E=P, As, Ter=2,6‐dimesitylphenyl) can undergo a one‐electron‐oxidation utilizing silver salts of weakly coordinating anions such as [AgLn][B(C6F5)4] (L=donor solvents) to afford the novel cyclic radical cations, [E(μ‐NTer)2E]+. ( 3 +.). When smaller and more basic anions were employed in the reaction, the anions were found to form covalent bonds to the radical centers yielding dipnictadiazanes, [FP(μ‐NTer)2PF] ( 5 ) and [(CF3CO2)P(μ‐NTer)2P(CF3CO2)] ( 6 ). A two‐electron oxidation process, resulting in the formation of dications of the type [E(μ‐NTer)2E]2+, could not be observed. Computational and EPR data revealed that the spin density is almost completely localized at the two heavier pnictogen centers E of the former 1,3‐dipnictadiazane‐1,3‐diyls. The bonding situation in the radical cations features a rare example of a transannular one‐electron π bond without having a σ bond.  相似文献   

6.
A carbon paste electrode was modified with 2‐(4‐Oxo‐3‐phenyl‐3,4‐dihydroquinazolinyl)‐N′‐phenyl‐hydrazinecarbothioamide, magnetic core? shell Fe3O4@SiO2/MWCNT nanocomposite and ionic liquid (n‐hexyl‐3‐methylimidazolium hexafluoro phosphate). The electro‐oxidation of hydrazine at the surface of the modified electrode was studied using electrochemical approaches. This modified electrode offers a considerable improvement in voltammetric sensitivity toward hydrazine, compared to the bare electrode. Square wave voltammetry (SWV) exhibits a linear dynamic range from 7.0×10?8 to 5.0×10?4 M and a detection limit of 40.0 nM for hydrazine. The diffusion coefficient and kinetic parameters (such as electron transfer coefficient and the heterogeneous rate constant) for hydrazine oxidation were also determined. The prepared modified electrode exhibits a very good resolution between the voltammetric peaks of hydrazine and phenol that makes it suitable for the detection of hydrazine in the presence of phenol in real samples.  相似文献   

7.

The Carotenoid S is a new C30 bonded silica stationary phase, intended for reversed-phase chromatographic applications, which is more hydrophobic and consequently shows stronger retention in comparison to conventionally used C18 stationary phases. We compared the non-polar selectivities of the columns for homologous alkylbenzenes in acetonitrile—water and methanol–water mobile phases and polar reversed-phase selectivities employing the interaction indices and the Linear Free Energy Relationship models. Further, we investigated possibilities of separations of structurally closely related compounds in the groups of phenolic acids, flavones, phthalic acids and related compounds and of acylglycerols on the new C30 column and with different types of columns for reversed-phase chromatography, including shorter alkyl C4, C8, C18 and phenyl bonded stationary phases. The C30 column has in some aspects properties similar to the non-endcapped Nova-Pak column for separation of some acylglycerols with equal equivalent carbon numbers, but enables separations of longer chain triacylglycerols in a single gradient run.

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8.
A reversed‐phase high‐performance liquid chromatography method for the simultaneous determination of jatrorrhizine, palmatine, and berberine in Huangbo, the dried bark of Chinese Corktree, was established by using 1‐hexyl‐3‐methylimidazolium tertafluoroborate as a mobile phase additive. The chromatographic behavior of the three compounds on the C18 column was studied with four different types of 1‐alkyl‐3‐methylimidazolium‐based ionic liquids as the mobile phase additives. The effect of 1‐hexyl‐3‐methylimidazolium tertafluoroborate was the best in the four investigated ionic liquids. The concentration of 1‐hexyl‐3‐methylimidazolium tertafluoroborate and the pH of the mobile phase, which influenced the chromatographic behaviors of the three bioactive compounds, were investigated. The linearity, precision, accuracy, repeatability, limit of detection, and quantification of the proposed method were found to be satisfactory. To explain the role of ionic liquids as the mobile phase additives, the possible mechanism was also explored and discussed.  相似文献   

9.
The title compound, 2,9‐bis(3‐nitro­phenyl)‐1‐aza­tri­cyclo[3.3.1.13,7]­decan‐4‐one, C21H19N3O5, has a tricyclic structure. The torsion angles may be used to describe the relationship of the carbonyl group to the adjacent faces, whereby it is seen that the angles on the face of the aryl­piperidinone side [122.0 (3) and ?122.0 (3)°] are greater than those on the cyclo­hexanone side [?119.8 (4) and 119.9 (4)°]. Although these differences may explain a facial selectivity during nucleophilic addition to the carbonyl group, the presence of the aryl rings is probably also important.  相似文献   

10.
The C‐terminal octapeptide of cholecystokinin (CCK8) includes some easily oxidizable amino acids. The oxidation of CCK8 by reactive oxygen species (ROS) such as hydrogen peroxide (H2O2) and hydroxyl radicals (OH?) was investigated using reversed‐phase high performance liquid chromatography (RP‐HPLC) and subsequent electrospray ionization mass spectrometry. The mechanism of oxidation of CCK8 in the H2O2 system differed from that of CCK8 in the Fenton system, in which OH? are produced. In the H2O2 system, 28Met and 31Met were oxidized to methionine sulfoxide, and no further oxidation or degradation/hydrolysis occurred. On the other hand, in the Fenton system, 28Met and 31Met residues were oxidized to methionine sulfone via the formation of methionine sulfoxide. In addition, the oxidized product was observed at the Trp residue but not at the Tyr residue, and small peptide fragments from CCK8 were observed in the Fenton system. From these results, it was concluded that 28Met and 31Met residues of CCK8 are susceptible to oxidation by ROS. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

11.
In the course of our studies of trinuclear osmium cluster complexes with bridging sulfido and hydrido ligands, the new compounds Os3(μ‐H)(μ‐SR)(CO)9(PHCy2) (Cy = cyclo­hexyl) with R = phenyl, (I) (nona­carbonyl‐1κ3C,2κ3C,3κ3C‐di­cyclo­hexyl­phosphine‐3κP‐μ‐hydrido‐1:2κ2H‐μ‐phenyl­thio‐1:2κ2Striangulo‐triosmium), [Os3H(C6H5S)(C12H23P)(CO)9], and R = naphthyl, (II) [nona­carbonyl‐1κ3C,2κ2C,3κ4C‐di­cyclo­hexyl­phosphine‐2κP‐μ‐hydrido‐1:2κ2H‐μ‐(2‐naphthyl­thio)‐1:2κ2Striangulo‐triosmium], [Os3H(C10H7S)(C12H23P)(CO)9], were prepared. We report on these two phosphine‐substituted complexes, which exhibit perceptible changes of the Os—Os bond parameters due to the ligand‐substitution pattern.  相似文献   

12.
A novel family of four 1‐bromo‐2,6‐bis{[(λ5‐phosphanylidene)imino]methyl}benzene ligands has been synthesized and characterized. The phosphiniminomethyl substituents are decorated with either three phenyl groups, two phenyl and one cyclohexyl group, one phenyl and two cyclohexyl groups, or three cyclohexyl groups. Each ligand was metallated using zero‐valent nickel through an oxidative addition to form a family of organonickel(II) complexes, namely (2,6‐bis{[(triphenyl‐λ5‐phosphanylidene)imino]methyl}phenyl‐κ3N,C1,N′)bromidonickel(II) dichloromethane hemisolvate, [NiBr(C44H37N2P2)]·0.5CH2Cl2, (2,6‐bis{[(cyclohexyldiphenyl‐λ5‐phosphanylidene)imino]methyl}phenyl‐κ3N,C1,N′)bromidonickel(II) diethyl ether hemisolvate, [NiBr(C44H49N2P2)]·0.5C4H10O, (2,6‐bis{[(dicyclohexylphenyl‐λ5‐phosphanylidene)imino]methyl}phenyl‐κ3N,C1,N′)bromidonickel(II), [NiBr(C44H61N2P2)], and (2,6‐bis{[(tricyclohexyl‐λ5‐phosphanylidene)imino]methyl}phenyl‐κ3N,C1,N′)bromidonickel(II), [NiBr(C44H73N2P2)]. This family of complexes represents a useful opportunity to investigate the impact of incrementally changing the steric characteristics of a complex on its structure and reactivity.  相似文献   

13.
A silica‐based reversed‐phase stationary phase bonding with phenyl and tetrazole groups was synthesized by thiol‐epoxy ring opening reaction. The bonded groups could not only provide hydrophobic interaction, but also π–π, hydrogen bonding, electrostatic interactions, and so on. The results of characterization with elemental analysis and solid‐state 13C cross‐polarization magic‐angle‐spinning NMR spectroscopy indicated the successful preparation of phenyl/tetrazole sulfoether bonded stationary phase. Chromatographic evaluation revealed that phenyl/tetrazole sulfoether bonded stationary phase behaved well under the reversed‐phase mode. The column parameters (H, S*, A, B, and C) showed different selectivity compared with some typical commercial columns, and it was validated by the separation of estrogen, ginsenoside, alkaloid samples. Based on the different selectivity between phenyl/tetrazole sulfoether bonded stationary phase and C18 columns, phenyl/tetrazole sulfoether bonded stationary phase also showed potential to construct a 2D reversed‐phase liquid chromatography system with C18. And it was verified by the separation of corydalis tuber and curcuma zedoary extracts.  相似文献   

14.
We studied the time‐of‐flight secondary ion mass spectrometry fragmentation mechanisms of polystyrenes—phenyl‐fluorinated polystyrene (5FPS), phenyl‐deuterated polystyrene (5DPS), and hydrogenated polystyrene (PS). From the positive ion spectra of 5FPS, we identified some characteristic molecular ion structures with isomeric geometries such as benzylic, benzocyclobutene, benzocyclopentene, cyclopentane, and tropylium systems. These structures were evaluated by the B3LYP‐D/jun‐cc‐pVDZ computation method. The intensities of the C7H2F5+ (m/z = 181), CyPent‐C9H3F4+ (m/z = 187), CyPent‐C9H4F5+ (m/z = 207), and CyPent‐C9H2F5+ (m/z = 205) ions were enhanced by resonance stabilization. The positive fluorinated ions from 5FPS tended to rearrange and produce fewer fluorine‐containing molecular ions through the loss of F (m/z = 19), CF (m/z = 31), and CF2 (m/z = 50) ion fragments. Consequently, the fluorine‐containing polycyclic aromatic ions had much lower intensities than their hydrocarbon counterparts. We propose the fragmentation mechanisms for the formation of C5H5+, C6H5+, and C7H7+ ion fragments, substantiated with detailed analyses of the negative ion spectra. These ions were created through elimination of a pentafluoro‐phenyl anion (C6F5) and H+, followed by a 1‐electron‐transfer process and then cyclization of the newly generated polyene with carbon‐carbon bond formation. The pendant groups with elements of different electronegativities exerted strong influences on the intensities and fragmentation processes of their corresponding ions.  相似文献   

15.
Although the cyclo‐P6 complex [(Cp*Mo)2(μ,η66‐P6)] ( 1 ) was reported 30 years ago, little is known about its chemistry. Herein, we report a high‐yielding synthesis of 1 , the complex 2 , which contains an unprecedented cyclo‐P10 ligand, and the reactivity of 1 towards the “naked” cations Cu+, Ag+, and Tl+. Besides the formation of the single oxidation products 3 a,b which have a bisallylic distorted cyclo‐P6 middle deck, the [M( 1 )2]+ complexes are described which show distorted square‐planar (M=Cu( 4 a ), Ag( 4 b )) or distorted tetrahedral coordinated (M=Cu( 5 )) M+ cations. The choice of solvent enabled control over the reaction outcome for Cu+, as proved by powder XRD and supported by DFT calculations. The reaction with Tl+ affords a layered two‐dimensional coordination network in the solid state.  相似文献   

16.
A relatively new stationary phase containing a polar group embedded in a hydrophobic backbone (i.e., ACE ® C18‐amide) was evaluated for use in supercritical fluid chromatography. The amide‐based column was compared with columns packed with bare silica, C18 silica, and a terminal‐amide silica phase. The system was held at supercritical pressure and temperature with a mobile phase composition of CO2 and methanol as cosolvent. The linear solvation energy relationship model was used to evaluate the behavior of these stationary phases, relating the retention factor of selected probes to specific chromatographic interactions. A five‐component test mixture, consisting of a group of drug‐like molecules was separated isocratically. The results show that the C18‐amide stationary phase provided a combination of interactions contributing to the retention of the probe compounds. The hydrophobic interactions are favorable; however, the electron donating ability of the embedded amide group shows a large positive interaction. Under the chromatographic conditions used, the C18‐amide column was able to provide baseline resolution of all the drug‐like probe compounds in a text mixture, while the other columns tested did not.  相似文献   

17.
A kind of new lanthanocene complex with an ansa carbonous‐bridged cyclopentadienyl/aromatic heterocycle ligand was prepared and characterized. Based on the data of elemental analyses, MS and IR, they were presumed to be solvent‐free complexes (cyclo‐C4H3SCMe2C5H4)2LnCl [Ln = Er (1), Dd ( 2 ), Y ( 3 ), Sm ( 4 )]. These complexes were effective for the polymerization of methyl methacrylate in the presence of co‐catalyst. When AlEt3 and NaH (nanometric) were used as different co‐catalysts, the lanthanocene complexes 1–4 showed different catalytic behavior. These differences resulted from the formation of different active species. The catalyst system (cyclo‐C4H3SCMe2C5H4)2LnCl/NaH (nanometric) showed high catalytic activity (yield ≥ 95% and Mη > 105) in a short time at the ambient temperature. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

18.
The mass spectra of phenyl 2-pyridyl, phenyl 3-methoxy-2-pyridyl, phenyl 4-methoxy-2-pyridyl, phenyl 5-methoxy-2-pyridyl, phenyl 6-methoxy-2-pyridyl ketones, phenyl 3-pyridyl and phenyl 6-methoxy-3-pyridyl ketones, and phenyl 4-pyridyl ketone were studied. The major fragmentation pathway of all the ketones results in the formation of[C6H5CO]+ and [C5H4NCO]+ type ions. Another fragmentation path is the loss of carbon monoxide with formation of an [M ? CO]+ ion after skeletal rearrangement.  相似文献   

19.
The title compounds, [Cr(C12H10)(CO)3] and [Cr2(C12H10)(CO)6], serve as a fundamental standard of comparison for other mono‐ and polysubstituted (η6‐bi­phenyl)­tri­carbonyl­chromium compounds. (η6‐Bi­phenyl)­tri­carbonyl­chromium has a typical piano‐stool coordination about the Cr center, and the dihedral angle between the planes of the phenyl rings is 23.55 (5)°. The corresponding angle in μ‐(η66)‐bi­phenyl‐bis­(tri­carbonyl­chromium) is 0° because the mol­ecule occupies a crystallographic inversion center; the Cr atoms reside on opposite sides of the bi­phenyl ligand. Density functional theory and natural bonding orbital theory analyses were used to scrutinize the geometry of these and closely related compounds to explain important structural features.  相似文献   

20.
Crystallization experiments with the dinuclear chelate ring complex di‐μ‐chlorido‐bis[(η2‐2‐allyl‐4‐methoxy‐5‐{[(propan‐2‐yloxy)carbonyl]methoxy}phenyl‐κC1)platinum(II)], [Pt2(C15H19O4)2Cl2], containing a derivative of the natural compound eugenol as ligand, have been performed. Using five different sets of crystallization conditions resulted in four different complexes which can be further used as starting compounds for the synthesis of Pt complexes with promising anticancer activities. In the case of vapour diffusion with the binary chloroform–diethyl ether or methylene chloride–diethyl ether systems, no change of the molecular structure was observed. Using evaporation from acetonitrile (at room temperature), dimethylformamide (DMF, at 313 K) or dimethyl sulfoxide (DMSO, at 313 K), however, resulted in the displacement of a chloride ligand by the solvent, giving, respectively, the mononuclear complexes (acetonitrile‐κN)(η2‐2‐allyl‐4‐methoxy‐5‐{[(propan‐2‐yloxy)carbonyl]methoxy}phenyl‐κC1)chloridoplatinum(II) monohydrate, [Pt(C15H19O4)Cl(CH3CN)]·H2O, (η2‐2‐allyl‐4‐methoxy‐5‐{[(propan‐2‐yloxy)carbonyl]methoxy}phenyl‐κC1)chlorido(dimethylformamide‐κO)platinum(II), [Pt(C15H19O4)Cl(C2H7NO)], and (η2‐2‐allyl‐4‐methoxy‐5‐{[(propan‐2‐yloxy)carbonyl]methoxy}phenyl‐κC1)chlorido(dimethyl sulfoxide‐κS)platinum(II), determined as the analogue {η2‐2‐allyl‐4‐methoxy‐5‐[(ethoxycarbonyl)methoxy]phenyl‐κC1}chlorido(dimethyl sulfoxide‐κS)platinum(II), [Pt(C14H17O4)Cl(C2H6OS)]. The crystal structures confirm that acetonitrile interacts with the PtII atom via its N atom, while for DMSO, the S atom is the coordinating atom. For the replacement, the longest of the two Pt—Cl bonds is cleaved, leading to a cis position of the solvent ligand with respect to the allyl group. The crystal packing of the complexes is characterized by dimer formation via C—H…O and C—H…π interactions, but no π–π interactions are observed despite the presence of the aromatic ring.  相似文献   

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