共查询到20条相似文献,搜索用时 31 毫秒
1.
57Fe NMR spectra of 35 organoiron complexes predominantly of the type [Fe(CO) 3(diene)] have been measured by direct detection at 2.9 MHz and at natural isotope abundance (2.2%). The 57Fe chemical shift range so far observed is 3000 ppm, corresponding to about 9 KHz. The majority of the resonances are at higher frequency than that of Fe(CO) 5, which is proposed as a secondary standard. The 57Fe resonance frequencies are also reported as ratios relative to the 73Ge frequency of GeCl 4.The 57Fe shielding is discussed qualitatively in terms of charge distribution in the complexes, very large deshielding effects being observed for cationic olefinic ligands. For η 4-diene complexes, the shielding also depends upon ligand geometry and decreases with increasing ring size or CCC bond angle. Two types of ferrocenylcarbenium ions may be distinguished, indicated by high- or low-frequency shifts relative to ferrocene. For a number of [Fe(CO) 3(olefin)] complexes 1J( 57Fe, 13C) coupling constants involving the carbonyl carbon are also reported. 相似文献
2.
α-Hydroxyisopropylferrocene, HPF, was synthesized in good yield and polymerized at 20°C with either SnCl 4 or BF 3OEt 2. The polymerization proceeds by self-alkylation of the stable intermediate ferrocenylcarbenium ion on the cyclopentadienyl ring to form oligomers that contain both homoannular and heteroannular links. The unusually high stability of the α-isopropylferrocenylcarbenium ion was demonstrated by synthesizing and isolating α-isopropylferrocenylcarbenium tetrafluoborate from HPF and using it to initiate the polymerization of styrene. Initiation was successful at 20° and at 0°C, but no polymerization occurred ?78°C. The condensation of ferrocene and acetone in the presence of AlCl 3 gave oligomers having structures very similar to those obtained from the cationic polymerization of isopropenylferrocene. 相似文献
3.
Herein, a simple electrochemical sensor was fabricated for sensing Hg 2+ ions by using electrochemically reduced p‐nitrobenzoic acid molecules modified (ERpNBA) glassy carbon electrode (GCE). The modified electrode was applied for the determination of Hg 2+ ions by using differential pulse anodic stripping voltammetry (DPASV). Experimental parameters such as concentration of p‐nitrobenzoic acid used for electrode modification, pH, accumulation time and deposition potential used for the determination of Hg 2+ ions were optimized. The strong interaction between the Hg 2+ ions and the lone pair of electrons on the nitrogen atoms of ERpNBA molecules leads to highly selective adsorption of Hg 2+ ions on the modified electrode. Under the optimum experimental conditions, the sensor showed higher sensitivity and very low detection limit for Hg 2+ ions than other metal ions such as Cd 2+, Pb 2+ and Zn 2+ ions. The LOD for Hg 2+ ions was 240 pM which is below the guideline value given by the World Health Organization and the earlier reports. 相似文献
4.
Some investigations concerning the decolorization of Acid Red G azo dye by photooxidation with hydrogen peroxide were performed.
The influences of pH, oxidant concentration, and the presence of Fe 2+ or other metal ions (Co 2+, Cu 2+, Ni 2+, Mn 2+) as potential catalysts, were investigated. The best results were obtained in the presence of ferrous ions in acid and neutral
media. The other ions are not as effective as Fe 2+ for dye decolorization. Co 2+ and Cu 2+ ions have a catalytic action, at low concentration, within a wide range of pH. Ni 2+ and Mn 2+ ions have no catalytic effect in photooxidation with hydrogen peroxide at acid Ni 2+ and Mn 2+ ions have no catalytic effect in photooxidation with hydrogen peroxide at acid pH values, but show a weak action in alkaline
media. 相似文献
5.
p- tert-Butyloctahomotetraoxacalix[8]arene (LH 8) reacts with uranyl nitrate hexahydrate in the presence of rubidium hydroxide to give a mixed complex that can be viewed as a tetrauranate dimer [(UO 2) 4(LH 4) 2(OH) 4] containing four disordered rubidium ions and water molecules. Two uranyl ions are complexed in an “external” fashion by each macrocycle, each of them bound to two phenoxide groups and one ether group, as well as to two bridging hydroxide ions. The latter ensure the formation of a dimeric capsule that contains the disordered set of alkali metal ions. Apart from water molecules, the Rb + ions are bound to the uranyl oxo groups directed towards the inner cavity, and to phenol and ether oxygen atoms from the macrocycle. The resulting octanuclear complex presents an unprecedented geometry evidencing the assembling potential of uranyl ions. p-tert-Butyloctahomotetraoxacalix[8]arene (LH 8) reacts with uranyl nitrate hexahydrate in the presence of rubidium hydroxide to give a mixed complex that can be viewed as a tetrauranate dimer [(UO 2) 4(LH 4) 2(OH) 4] containing four disordered rubidium ions and water molecules. Two uranyl ions are complexed in an “external” fashion by each macrocycle, each of them bound to two phenoxide groups and one ether group, as well as to two bridging hydroxide ions. The latter ensure the formation of a dimeric capsule that contains the disordered set of alkali metal ions. Apart from water molecules, the Rb +| ions are bound to the uranyl oxo groups directed towards the inner cavity, and to phenol and ether oxygen atoms from the macrocycle. The resulting octanuclear complex presents an unprecedented geometry evidencing the assembling potential of uranyl ions. 相似文献
6.
Heavy metal ions such as Hg and Pb are hazardous due to very high toxicity, mobility, and ability to accumulate through the food chain or atmosphere in the environment system. Therefore, ultrasensitive determination of mercury and lead is important to provide an evaluation index of ions in aqueous environment. This paper describes the investigation of surface modified quantum dots (QDs) as a sensing receptor for Hg 2+ and Pb 2+ ion detection by optical approach. Water-soluble L-cysteine-capped CdS QDs have been synthesized in aqueous medium. These functionalized nanoparticles were used as a fluorescence sensor for Hg 2+ and Pb 2+ ions, involved in the fluorescence quenching. The effect of foreign ions on the intensity of CdS QDs showed a low interference response toward other metal ions except Cu 2+ and Fe 2+ ions. The limit of detection (LOD) of this system is found to be 1.0 and 3.0 nM for Hg 2+ and Pb 2+ ions, respectively. 相似文献
7.
The adsorption of metal ions such as Ce 3+, Sm 3+, Eu 3+ and Gd 3+ ions on activated charcoal has been studied as a function of pH. The adsorption mechanism of these ions is discussed in terms of hydrolyzed species formed in aqueous solution at different pH. 相似文献
8.
A corona discharge atmospheric pressure ionization source generates the reagent ions, OH ? and O ? ions in addition to better known O 2? ions, when ambient air is used as the carrier. All three ions are gas-phase bases that could form negative ions from organics via proton abstraction. Ionization of simple aromatic hydrocarbons by O 2? is thermodynamically not feasible. Simple aromatic hydrocarbons are ionized only by O ? and/or OH ? to form [M ? H] ? ions. However, [M ? H] ? ions do not appear in the mass spectrum as they undergo stabilization via clustering with predominantly oxygen atoms. 相似文献
9.
Collisions of organofluorine ions at a metal surface result in efficient emission of adsorbate species as gas-phase ions. The experiments are done at 120° scattering angle in a hybrid (BQ) mass spectrometer; the primary ions, mass-selected by a magnetic sector (B), are allowed to collide with a target at a selected kinetic energy in the tens of eV range and the emitted ions are mass-analyzed using a quadrupole mass filter ( Q). It is proposed that the impinging ions undergo neutralization accompanied by desorption of hydrocarbon ions and that the amount of internal energy deposited in the desorbed ions is strongly dependent on the collision energy and affects their degree of fragmentation. Competing processes include reflection and fragmentation of the colliding particle, along with such ion/adsorbate reactions as hydrogen atom abstraction by the fluorinated ion. Small even-electron ions, such as [CHF 2] + and [C 2H 2F] + are more effective in promoting chemical sputtering of the surface adsorbate as compared to larger ions (e.g. [C 3F 5] +) and odd-electron ions (e.g. [C 2F 4] +˙ and [C 2HF 2] +˙). At low energies some odd-electron fluorinated ions undergo collision without any secondary ions being emitted from the surface. In these cases the parent ions are apparently neutralized, but without sufficient energy transfer to cause hydrocarbon ion desorption. Non-fluorinated organic ions yield fragment ions and ion/surface reaction products under the condition of these experiments, but do not cause significant desorption of hydrocarbon ions. 相似文献
10.
The role of nitrate ions in uranyl ions transport across TBP-kerosene oil supported liquid membranes (SLM) at varied concentrations of HNO 3 and NaNO 3 has been studied. It has been found that nitrate ions move faster compared to uranyl ions at the uranium feed solution concentrations studied. The nitrate to uranyl ions flux ratio vary from 355 to 2636 under different chemical conditions. At low uranium concentration the nitrate ions transport as HNO 3 · TBP, in addition to as UO 2(NO 3) 2 · 2TBP type complex species. The flux of nitrate ions is of the order of 12.10 · 10 –3 mol · m –2 · s –1 compared to that of uranium ions (4.56 · 10 –6 mol · m –2 · s –1). The permeability coefficient of the membrane for nitrate ions varies with chemical composition of the feed solution and is in the order of 2.5 · 10 –10 m –2 · s –1. The data is useful to estimate the nitrate ions required to move a given amount of uranyl ions across such an SLM and in simple solvent extraction. 相似文献
11.
Abstract The cation-exchange characteristics between Pb 2+ ions of aqueous solutions containing counter-anions (F ?, C1 ?) and Ca 2+ ions of synthetic hydroxyapatite samples have been investigated in detail under the conditions of low pH values (3.0, 4.0 and 5.0) by a normal batch method. Even at the low pH value of 3.0 the apatite structure in a solution containing F ? or C1 ? ions was maintained via a concurrent ion-exchange effect of Pb 2+ ions together with F ? or C1 ?ions, which are known to be exchangeable with OH- ions of the apatite. Moreover, it was found that Ca 2+ ions in the apatite sample can easily be exchanged for Pb 2+ ions almost without distinction between MI and M2 sites, assisted by the loosening effect of protons even at room temperature. Next, it was found that the hydroxyapatite samples are transformed into amorphous states by the reactions between Ca 2+ ions in the samples and Sn 2+ ions in the SnC1 2 acidic aqueous solutions with pH of 3.0 or below with a molar ratio of Sn 2+/Ca 2+ -1.0. The existence of hydroxyapatite as amorphism in acidic aqueous solutions such as SnC1 2 is quite interesting, because in general the hydroxyapatite has been found to be dissolved in acidic aqueous solutions. Moreover, the obtained amorphism are found to be stable up to at least 500 to 6OO°C but to be unstable in alkaline solutions. The characteristics of Sn 2+ ions are found to have been found to form crystalline Pb 2+ apatite even in be quite different from those of homologous Pb 2+ ions which have been found to form crystalline pb 2+ apatite even in such an acidic atmosphere. 相似文献
12.
Fixation of 137Cs, 144Ce, 60Co, 90Sr, 240Th and 233U from aqueous and phosphate media on bentonite clay was studied. The fixation of the radioactive ions on bentonite surfaces
was dependent on the pH behavior of the metal ions. A method was proposed to use bentonite as an absorbent of ions from simulated
radioactive waste as a treatment step. 相似文献
13.
Two monostyryl BODIPY derivatives that contain one or two bis(hydroxyamido)amino group(s) as the metal chelator have been prepared. The effects of various metal ions on their electronic absorption and fluorescence properties have been studied in detail in MeCN or in phosphate buffered saline (PBS). The results show that the derivative with two hydroxyamide chains can selectively detect Zn 2+ ions in MeCN. The compound and ions bind in a 1:1 stoichiometry with an association constant of 2.2(±0.1)×10 4 M ?1. The intensity of the fluorescence emission increases remarkably and is substantially blue‐shifted from 624 to 572 nm, owing to the inhibition of intramolecular charge transfer, thus allowing its use as a ratiometric fluorescent sensor for Zn 2+ ions. The derivative with four hydroxyamide chains behaves differently: It responds selectively toward Cd 2+ ions in phosphate buffered saline. The compound and ions bind in a 1:2 stoichiometry, with first and second association constants of 4.4(±0.9)×10 4 M ?1 and 1.3(±0.1)×10 4 M ?1, respectively. Upon the addition of 80 equivalents of Cd 2+ ions, the fluorescence quantum yield increases 15‐fold. Both of these compounds exhibit differential sensing of Zn 2+ and Cd 2+ ions and the associated color changes can be easily seen by the naked eye. 相似文献
14.
In this study, kumquat was first time used for synthesizing carbon dot structures (CDs) with the hydrothermal method. These newly synthesized CDs was characterized structurally and optically. The ion sensor application of the new CDs was carried out using 20 different metal ions. It was observed that CDs have high selectivity only for Fe3+ ions among the metal ions studied. Detection limit for Fe3+ ions was calculated as 0.70 µM. The results showed that these new CDs are highly selective against Fe3+ ions and have a very short response time such as 0.5 min. The Fe3+ ions selectivity of CDs was tested on real (tap water) samples. The results exhibited that this new CDs, obtained with green synthesis from Kumquat fruit without using chemical agents in one-pot simple and economical process, can be used as fluorometric sensor for detection of Fe3+ ions with high selectivity and sensitivity, low detection limit and rapid response time. 相似文献
15.
Laser-desorbed peptide neutral molecules were allowed to react with Fe + in a Fourier transform mass spectrometer, using the technique of laser desorption/chemical ionization. The Fe + ions are formed by laser ablation of a steel target, as well as by dissociative charge-exchange ionization of ferrocene with Ne +. Prior to reaction with laser-desorbed peptide molecules, Fe + ions undergo 20–100 thermalizin collisions with xenon to reduce the population of excited-state metal ion species. The Fe + ions that have not experienced thermalizing collisions undergo charge exchange with peptide molecules. Iron ions that undergo thermalizing collisions before they are allowed to react with peptides are found to undergo charge exchange and to form adduct species [M + Fe +] and fragment ions that result from the loss of small, stable molecules, such as H 2O, CO, and CO 2, from the metal ion-peptide complex. 相似文献
16.
Secondary ion mass spectra obtained by [Xe] + bombardment are compared with those obtained by [Ar] + bombardment. Although [Ar] + ions are commonly used as primary ions in secondary ion mass spectrometry for organic compounds, [Xe] + ions seem better as primary ions because they give a larger sputtering yield for a metal substrate than [Ar] + ions. Cationized molecular intensities of sucrose, raffinose and stachyose, and quasimolecular ion intensities of tuftsin and eledoisin related peptide are investigated using [Xe] + and [Ar] + bombardments. The observed molecular species are 2–4 times more intense for [Xe] + bombardment than for [Ar] + bombardment, although the secondary ion mass spectra are almost the same in both cases. 相似文献
17.
Piroxicam was found to be a highly selective carrier for uphill transport of Cu 2+ ions through a chloroform liquid membrane. The transport occurs via a counterflow of protons from the receiving phase to
the source phase. The effects of several parameters on the transport of Cu 2+ ions, such as the carrier concentration, pH of the source phase, composition of the receiving phase, and duration are described.
A high transport efficiency (98±2%) was provided by the carrier for Cu 2+ ions in a receiving phase of 0.01 mol l −1 sulfuric acid after 4 h. Different metal ion transport experiments showed that Cu 2+ ions were selectively transported over other ions, such as Co 2+, Ni 2+, Cd 2+, Pb 2+, Zn 2+, UO 22+ and ZrO 22+. In the presence of fluoride ions (used as a suitable masking agent in the source phase), the interfering effects of UO 22+ and ZrO 22+ ions were eliminated. The applicability of the method was tested on a real sample, and the results obtained show that it
is potentially useful for solvent extraction of copper. 相似文献
18.
We have carried out a selected ion flow tube (SIFT) study of the reactions of H 3O +, NO +, and O 2+ ions with several saturated and unsaturated aldehydes. This study is mainly directed toward providing the essential data for a projected SIFT mass spectrometry (SIFTMS) study of the volatile emissions from cooked meats, which always include aldehydes. Thus, it is necessary to know the rate coefficients and the product ions of the reactions of the above-mentioned ions, used as the precursor ions for SIFTMS analyses, with the aldehydes, if proper identification and quantification of the emitted species are to be achieved. The results of this study show that the reactions of H 3O + with the aldehydes, M, result in the protonated molecules MH + and for the saturated aldehydes also in (M - OH) + ions resulting from the loss of a H 2O molecule from the nascent MH + ion. The NO + reactions invariably proceed via the process of hydride ion, H −, transfer producing (M - H) + ions, but parallel minor association product ions NO + · M are observed for some of the unsaturated aldehyde reactions. The O 2+ reactions proceed by way of charge transfer producing nascent M + ions that partially dissociate producing fragment ions. Because water vapour is invariably present in real samples analysed by SIFTMS, the current experiments were also carried out following the introduction of humid laboratory air into the helium carrier gas of the SIFT. Thus, the reactions of the product ions that form hydrates were also studied as a prelude to future SIFTMS studies of the (humid) emissions from cooked meats. 相似文献
19.
Complexations of crown ethers with alkali metal ions have been investigated extensively by FAB mass spectrometry over the past decade, but very little attention has been paid to reactions of crown ethers with other classes of metal ions such as alkaline earth metal ions, transition metal ions and aluminum ions. Although fast atom bombardment ionization mass spectrometry has proven to be a rapid and convenient method to determine the binding interactions of crown ethers with metal ions, problems in reliabilities for quantitative measurements of” binding strength for the host-guest complexes have been described in the literature. Thus, in this paper, applications of FAB/MS for investigating the complexation of crown ethers with various classes of metal ions is discussed. Extensive fragmentations for neutral losses such as C 2H 4O or C 2H 4 molecules from the host-guest complexes could be observed. The reason is attributed to the energetic bombardment processes of FAB occuring in the formation of these complexes. Complexes of cyclen with metal ions also show neutral losses of C 2H 4NH molecules leading to fragment ions. Transition metal ions usually form (Crown + MCl) + type of ions, alkaline earth metal ions can form both (Crown + MCl) + and (Crown + MOH) + type of ions. But for aluminum ions, only (Crown + Al(OH) 2) + type of ions could he observed. 相似文献
20.
Potential energy curves have been computed for [C 2H 6] 2+ ions and the results used to interpret the conspicuous absence of these ions in 2E mass spectra and in charge-stripping experiments. The energies and structures of geometry-optimized ground-state singlet and excited-state triplet [C 2H 6] 2+ ions have been determined along with energies for different decomposition barriers and dissociation asymptotes. Although singlet and triplet [C 2H 6] 2+ ions can exist as stable entities, they possess low energy barriers to decomposition. Vertical Franck-Condon transitions, involving electron impact ionization of ethane as well as charge-stripping collisions of [C 2H 6] + ions, produce [C 2H 6] 2+ ions which promptly dissociate since they are formed with energies in excess of various decomposition barriers. Appearance energies computed for doubly-charged ethane fragment ions are in accordance with experimental values. 相似文献
|