Ce Cl Research Articles

Ultrathin 2D Cerium-Based Metal-Organic Framework Nanosheet That Boosts Selective Oxidation of Inert C(sp3 )H Bond through Multiphoton Excitation.

The development of methodologies for inducing and tailoring activities of catalysts is an important issue in various catalysis. The ultrathin 2D monolayer metal-organic framework (MOF) nanosheets with more accessible active sites and faster diffusion obtained by exfoliating 3D layered MOFs are of great potential as heterogeneous catalysts, but the rational design and preparation of 3D layered MOFs remains a grand challenge. Herein, a novel weak electrostatic interaction strategy to construct a 3D layered cerium-bearing MOF by coordinating chlorine-capped cerium nodes and linear photoactive methyl viologen (MV+ ) organic linkers is used. Under multiphoton excitation, the MV+ ligands and CeCl chromophores are triggered consecutively to form the high activity chlorine radical (Cl• ) for activation of inert C(sp3 )H bond through a hydrogen atom transfer. Benefiting from framework confinement effects, synergistic effects of two active sites and/or flexibility of the ultrathin framework nanosheets with high surface utilization, the observed activities increase in the order CeCl3 /MV+ < bulk 3D MOF crystals < 2D MOF nanosheets in photocatalysis. This work not only contributes a new strategy to construct 3D layered MOFs and their ultrathin nanosheets but also paves the way to use nanostructured MOFs to handle synergy of multiple molecular catalysts.

Imidazolin-2-iminato Cerium(IV) Chlorides: Synthesis, Structure and Electrochemical Properties.

The ligand field greatly affects the redox properties of cerium. Herein, cerium(III) and cerium(IV) complexes supported by imidazolin-2-iminato ligands were synthesized and structurally characterized, and their electrochemical properties were investigated. Silylamine elimination of cerium(III) amide Ce{N(SiMe3 )2 }3 with imidazolin-2-imine ImR NH (R=Mes, tBu, iPr) provided imidazolin-2-iminato cerium(III) complexes, [(ImMes N)(ImMes NH)Ce{N(SiMe3 )2 }2 ] (1), [(ImtBu N)2 (ImtBu NH)Ce{N(SiMe3 )2 }] (2) and [(ImiPr N)2 (ImiPr NH)Ce(μ-ImiPr N)]2 (4) in 71-85% yields. These cerium(III) complexes were successfully oxidized by Ph3 CCl or C2 Cl6 to afford imidazolin-2-iminato cerium(IV) chlorides, [(ImMes N)2 Ce{N(SiMe3 )2 }Cl] (5), [(ImtBu N)3 CeCl] (6) and [(ImiPr N)2 Ce(μ-ImiPr N)Cl]2 (7) in 70%-76% yields. All complexes were characterized by the single-crystal X-ray diffraction, which showed that 1, 2, 5 and 6 are monomers while 4 and 7 are dimers. The electrochemical studies indicated that the Ce(III/IV) couples for 5 and 6 are more negative than those of silylamido cerium(IV) complexes, and the Ce(III/IV) couples for 1 and 2 have a similar trend.

Simultaneous determination of four phenolic acids in traditional Chinese medicine by capillary electrophoresis-chemiluminescence.

Chlorogenic, ferulic, vanillic, and caffeic acids are phenolic acids found in natural drugs. They possess the biological activities of scavenging free radicals and inhibiting thrombus formation. Phenolic acids can inhibit the oxidation of low-density lipoprotein, as well as have anti-inflammatory effects. This paper reports for the first time a capillary electrophoresis–chemiluminescence (CE–CL) method for the simultaneous determination of the four phenolic acids found in traditional and proprietary Chinese medicine, including Lycium chinense Miller, Shuanghuanglian oral liquid, and Taraxacum mongolicum granules. Capillary electrophoretic separation was performed on a self-assembled CE–CL device with an uncoated fused-silica capillary (66 cm effective length, 50 μm i.d.), and the background electrolyte was composed of 3.0 × 10−5 M Ag(iii) (pH = 12.01), 3.0 mM luminol (pH = 9.20), and 10 mM sodium tetraborate solution. The injection time was 12 s (under gravity) and the separation voltage was 22 kV. The combination of solid-phase extraction (SPE) and CE–CL improves the sensitivity. Under optimal conditions, calibration graphs displayed a linear range between 0.625 and 20.0, 1.000 and 30.0, 0.150 and 1.50, and 0.045 and 1.00 μg mL−1 for chlorogenic, ferulic, vanillic, and caffeic acid, respectively. The detection limit ranged from 0.014 to 0.300 μg mL−1. The practicality of using the proposed method to determine the four target analytes in traditional Chinese medicine was also validated, in which recoveries ranged from 90.9% to 119.8%. Taken together, these results indicate that the developed method is sensitive and reliable. Furthermore, the method was successfully applied to real traditional Chinese medicine samples.

Ceric Cyclopentadienides Bearing Alkoxy, Aryloxy, Chlorido, or Iodido Co-Ligands.

A series of heteroleptic tris(cyclopentadienyl) CeIV complexes has been isolated and crystallographically characterized, revealing the broad accessibility of such organocerium(IV) compounds. The oxidation of complexes CpMe3 Ce(thf) and Cp'3 Ce(thf) (CpMe =C5 H4 Me, Cp'=C5 H4 SiMe3 ), bearing monosubstituted electron-poor cyclopentadienyl ligands, with 0.5 equivalents of 1,4-benzoquinone or C2 Cl6 gave the cerium(IV) hydroquinolate complexes CpMe3 Ce(OC6 H4 O)CeCpMe3 and Cp'3 Ce(OC6 H4 O)CeCp'3 , or the chloride complexes CpMe3 CeCl and Cp'3 CeCl, respectively; the iodide complex Cp'3 CeI was obtained from the reaction of Cp'3 Ce(thf) with elemental iodine. The behavior of Cp'3 CeCl in salt metathesis protocols employing alkali metal amides or alkyl, alkoxide, and aryloxide reagents was investigated, which gave rise to the robust and isolable cerium(IV) alkoxide Cp'3 Ce(OtBu). Trivalent [Cp'2 CeCl]2 was synthesized by AlMe4 →Cl exchange utilizing Cp'2 Ce(AlMe4 ) and AlMe2 Cl. The reactivity of [Cp'2 CeCl]2 towards the oxidants Ph3 CCl, C2 Cl6 , 1,4-benzoquinone, and I2 has been assessed, and has provided useful information on CeIII /CeIV redox deactivation pathways. In addition to X-ray structure analysis, all the complexes were characterized by NMR, DRIFT (diffuse reflectance IR Fourier transform), and UV/Vis spectroscopy as well as elemental analysis. The tetravalent compounds were further analyzed for their magnetic susceptibility by using Evans' method.

Mineralogical evolution and REE mobility during crystallisation of ancylite-bearing ferrocarbonatite, Haast River, New Zealand

Ferrocarbonatites from the lamprophyric Alpine Dyke Swarm, south Westland, New Zealand are composed of dolomite–calcite-albite–hematite and contain interstitial patches dominated by calcite–ancylite–barite–monazite–thorite–albite–aeschynite–analcime, interpreted as modified late-stage segregations. The dominant carbonate in the ferrocarbonatite is a ferroan dolomite that contains vermicular and blocky patches of calcite and a more Fe-rich ankerite. The calcite is interpreted as the product of exsolution or the by-product, with dolomite and hematite, of the oxidation of primary ankerite during interaction with hydrothermal fluids. Late stage ancylite-rich segregations have elevated 87Sr/86Sr compositions relative to host carbonatite suggesting they have crystallised from fluids that have equilibrated with host schist, but with the REE derived from fractionation of ferrocarbonatite. Mineral veining indicates this stage of crystallisation post-dated the ankerite to dolomite replacement.The carbonatites, as inferred from mineral associations, textures and carbonate geothermometry, have a complex history of recrystallisation from late stage, low temperature carbo-hydrothermal fluids. All carbonatitic phases have convex-upward chondrite normalised REE patterns enriched in Nd, and are relatively depleted in lighter LREE and in HREE. Depletion in La and Ce is attributed to either complementary enrichment in felsic magmas during initial separation of carbonatite, or more likely, to subsequent preferentially enhanced mobility of La– and Ce–Cl− complexes in low-temperature aqueous fluids.

Intervalence charge transfer luminescence: the anomalous luminescence of cerium-doped Cs₂LiLuCl₆ elpasolite.

The existence of intervalence charge transfer (IVCT) luminescence is reported. It is shown that the so called anomalous luminescence of Ce-doped elpasolite Cs2LiLuCl6, which is characterized mainly by a very large Stokes shift and a very large band width, corresponds to an IVCT emission that takes place in Ce(3+)-Ce(4+) pairs, from the 5de(g) orbital of Ce(3+) to 4f orbitals of Ce(4+). Its Stokes shift is the sum of the large reorganization energies of the Ce(4+) and Ce(3+) centers formed after the fixed-nuclei electron transfer and it is equal to the energy of the IVCT absorption commonly found in mixed-valence compounds, which is predicted to exist in this material and to be slightly larger than 10,000 cm(-1). The large band width is the consequence of the large offset between the minima of the Ce(3+)-Ce(4+) and Ce(4+)-Ce(3+) pairs along the electron transfer reaction coordinate. This offset is approximately 2√3 times the difference of Ce-Cl equilibrium distances in the Ce(3+) and Ce(4+) centers. It is shown that the energies of the peaks and the widths of IVCT absorption and emission bands can be calculated ab initio with reasonable accuracy from diabatic energy surfaces of the ground and excited states and that these can be obtained, in turn, from independent calculations on the donor and acceptor active centers. We obtained the energies of the Ce(3+) and Ce(4+) active centers of Ce-doped Cs2LiLuCl6 by means of state-of-the-art wave-function-theory spin-orbit coupling relativistic calculations on the donor cluster (CeCl6Li6Cs8)(11+) and the acceptor cluster (CeCl6Li6Cs8)(12+) embedded in a quantum mechanical embedding potential of the host. The calculations provide interpretations of unexplained experimental observations as due to higher energy IVCT absorptions, and allow to reinterpret others. The existence of another IVCT emission of lower energy, at around 14,000-16,000 cm(-1) less than the 5dt(2g) emission, is also predicted.

Highly sensitive analysis of four hemeproteins by dynamically-coated capillary electrophoresis with chemiluminescence detector using an off-column coaxial flow interface

Dynamic coating of the surface in capillary electrophoresis with chemiluminescence detection (CE-CL) using an off-column coaxial flow interface for the determination of four hemeproteins was developed. This method is based on the luminol-hydrogen peroxide reaction catalyzed by metalloproteins in alkaline medium. The experimental setup of the CE-CL system with the proposed off-column coaxial interface was evaluated by separation and detection of dopamine and catechol based on inhibition of the luminol-potassium ferricyanide reaction. Highly efficient separation of the two model compounds with symmetrical peak shape and satisfactory reproducibility was achieved by using this interface. In addition, in order to obtain a good resolution for hemeproteins, polyvinylpyrrolidone (PVP) combined with sodium dodecyl sulfate (SDS) were introduced as dynamic modifiers to reduce the unwanted adsorption of non-specific protein. Several parameters affecting the CE separation and CL detection were investigated in detail. Under the optimized conditions, a mixture of the four hemeproteins (horseradish peroxidase (HRP), catalase (Cat), myoglobin (Mb) and cytochrome C (Cyt C)) could be well separated within 20 min. The linear ranges of the four proteins were 5.7 × 10(-8) to 1.1 × 10(-6) mol L(-1) for HRP, 4.0 × 10(-8) to 2.0 × 10(-6) mol L(-1) for Cat, 1.1 × 10(-10) to 5.6 × 10(-8) mol L(-1) for Mb, and 3.8 × 10(-7) to 7.7 × 10(-6) mol L(-1) for Cyt C. The limits of detection (LODs) (S/N = 3) for HRP, Cat, Mb and Cyt C were 2.2 × 10(-8) mol L(-1) (104.5 amol), 1.6 × 10(-8) mol L(-1) (74 amol), 5.6 × 10(-11) mol L(-1) (0.26 amol), and 1.95 × 10(-7) mol L(-1) (0.89 fmol), respectively. The proposed method has been successfully applied to the analysis of low-level Mb in a spiked human urine sample and the recoveries were above 97%. Our primary result demonstrated that the proposed CE-CL method has great potential for Mb determination in clinical diagnosis.

Quantum dot-enhanced chemiluminescence detection for simultaneous determination of dopamine and epinephrine by capillary electrophoresis

A sensitive method based on quantum dot (QD)-enhanced capillary electrophoresis–chemiluminescence (CE–CL) detection was developed for simultaneous determination of dopamine (DA) and epinephrine (E). In this work, CdTe QD was added into the running buffer of CE to catalyze the post-column CL reaction between luminol and hydrogen peroxide, achieving higher CL emission. Negative peaks were produced due to the inhibitory effects on CL emission from DA and E eluted from the electrophoretic capillary. The decrease in CL intensity was proportional to the concentration of DA and E in the range of 8.0×10−8–5.0×10−6M and 4.0×10−8–5.0×10−6M, respectively. Detection limits for DA and E were 2.3×10−8M and 9.3×10−9M, respectively. Using this method, the levels of DA and E in human urine from healthy donors were determined.

Catena-Poly[[triaqua-chlorido-μ(3)-malonato-cerium(III)] hemihydrate

The asymmetric unit of the title compound, {[Ce(C3H2O4)Cl(H2O)3]·0.5H2O}n, contains a Ce3+ atom coordinated by a chloride anion, three water mol­ecules and a malonate ligand, and one water mol­ecule of crystallization with a factor of occupancy of 50%. The malonate ligand is bonded to three different symmetry-related metal atoms yielding a one-dimensional coordination polymer running parallel to the a axis. A supra­molecular network composed of strong and highly directional O—H⋯O and O—H⋯Cl hydrogen bonds ensures a close and effective packing of adjacent polymeric chains.

Bis({tris[2-(3,5-di-tert-butyl-2-oxidobenzylideneamino)ethyl]amine}cerium(III)) diethyl ether solvate

The title compound, 2[Ce(C51H75N4O3)]·C4H10O, was obtained in high yield (92%) by reduction of (TRENDSAL)CeIVCl [TRENDSAL is N,N′,N′′-tris­(3,5-di-tert-butyl­salicyl­ide­natoamino)­triethyl­amine] with potassium in THF. The bulky tripodal TRENDSAL ligand effectively encapsulates the central CeIII cation with a Ce—N(imine) distance of 2.860 (2) Å and an average C—N(amine) distance of 2.619 Å within a distorted monocapped octahedral coordination.

Advances and analytical applications in chemiluminescence coupled to capillary electrophoresis

The present review presents the state of the art of the developments, key strategies and analytical applications of chemiluminescence detection coupled to CE (CE-CL). Different parts considering the most common CL systems have been included, such as the tris(2,2'-bipyridine)ruthenium(II) system, the luminol and derivatives reaction, the peroxyoxalate CL or direct oxidations. New advances in homemade configurations and applications in different fields such as clinical, pharmaceutical, environmental and food analysis have been included. The focus is on studies which appeared from 2000 to the end of 2009.

CeO2 Nanorod–TiO2 Nanotube Hybrid Nanostructure

CeO2 nanorods with a polycrystalline structure were prepared by galvanostatic electrodeposition using TiO2 nanotube arrays as templates. The heterogeneous nucleation and subsequent growth of CeO2 nanorods are an electric field‐assisted process, which depend upon the current density and electrolyte concentration. At low electric field intensity, amorphous nanoparticles are formed; whereas, at high electric field intensity, a layer of dense film is deposited (caused by the overgrowth of CeO2). By using an optimum electrochemical condition, namely current density of 0.1 mA/cm2 and Ce(Cl)3 solution concentration of 0.5 mmol/L, moderate electric field intensity can be obtained to grow the CeO2 nanorod–TiO2 nanotube hybrid nanostructure.

Sazonalidade e variabilidade espacial da qualidade da água na Lagoa do Apodi, RN

Neste trabalho se propõe avaliar a qualidade da água da Lagoa do Apodi, RN, em pontos compreendidos em todo o seu espelho, com ênfase ao monitoramento da qualidade da água sob influência da bacia urbana da cidade de Apodi e do aporte de materiais trazidos pelas águas continentais que adentram e eutrofizam a lagoa, em períodos extremos de temperatura e de precipitação. Amostras sistemáticas no espelho da lagoa foram coletadas seguindo-se seu formato ou ao longo de seu leito. A condutividade elétrica da água da Lagoa varia em todo o seu espelho, principalmente nas extremidades oeste e sudeste, aumentando após o início do período seco e diminuindo após a chegada das chuvas. Há uma grande variabilidade espacial nas características físicas e químicas, sobretudo para pH, CE, RAS e teores de Na e Cl; pode-se inferir, também, que nas águas da lagoa os íons encontrados em maiores níveis foram o cloreto e o sódio, tanto para os pontos de coleta como para a época de coleta. A variação na qualidade bacteriológica da água compromete a balneabilidade da Lagoa do Apodi, principalmente logo após o período das chuvas.

High pressure optical spectroscopy of Ce 3+-doped Cs 2NaLuCl 6

The study of the f ↔ d transition on Ce 3+-doped Cs 2NaLuCl 6, through the absorption and emission spectra at high pressure, allows us to conclude that the equilibrium Ce–Cl bond distance in the excited state is shorter than in the ground state. The observed band shifts of −530 ± 20 cm −1/GPa and −415 ± 10 cm −1/GPa in absorption and emission, respectively, reveal reduction of the Stokes shift and the spin–orbit interaction with pressure.

Quantification of Carcinoembryonic Antigen by Capillary Electrophoresis–Chemiluminescence Detection using Internal Standard Method

Sensitive determination of tumor marker carcinoembryonic antigen (CEA) by capillary electrophoresis–chemiluminescence detection (CE-CL) has been developed using an internal standard method. Parameters affecting the CE separation and CL detection were systematically optimized. Under the optimal conditions, the free horseradish peroxidase (HRP)–labeled antibody (Ab*), the bound Ab*-antigen complex (Ab*-Ag), and HRP used as internal standard were well separated within 5 min. The proposed method was successfully applied for the quantification of CEA in human sera obtained from both healthy persons and patients.

Sensitive detection of tumor marker CA15‐3 in human serum by capillary electrophoretic immunoassay with chemiluminescence detection

A new and sensitive non-competitive immunoassay (IA) for tumor marker carbohydrate antigen 15-3 (CA15-3) by CE coupling with ECL detection has been developed. This method is based on luminol-H(2)O(2 )reaction catalyzed by horseradish peroxidase (HRP). The optimum CE separation and CL detection conditions were investigated. After the non-competitive immunoreaction, the free HRP-labeled CA15-3 antibody (Ab*) and the bound Ab*-antigen (Ab*-Ag) complex were separated in a separation capillary and then catalyzed the CL reaction of luminol and H(2)O(2 )in a reaction capillary following the separation capillary. The calibration curve based on the peak areas of Ab*-Ag complex plotted against the concentrations of CA15-3 is in the range of 0-250 U/mL with a correlation coefficient of 0.9983 and the detection limit is 0.035 U/mL (S/N = 3). The response for five consecutive injections of 125 U/mL CA15-3 resulted in RSDs of 0.83% and 3.1% for the migration time and the peak area, respectively. The method was successfully used for the quantification of CA15-3 in human sera obtained from healthy persons and from patients with breast cancer.

Capillary electrophoretic immunoassay for alpha-fetoprotein with chemiluminescence detection

A capillary electrophoretic immunoassay with chemiluminescence detection (CEIA–CL) using a non-competitive format for analyzing tumor marker alpha-fetoprotein (AFP) has been developed. In this method, antigen (Ag) AFP reacts with an excess amount of horseradish peroxidase (HRP)-labeled antibody (Ab*). The free Ab* and the bound Ab*–Ag complex produced in the solution are separated by CE in a separation capillary. Then they catalyze the reaction of enzyme substrate luminol and H 2O 2 in a reaction capillary following the separation capillary. Parameters affecting the CE separation and CL detection were investigated. Under the optimal conditions, the free Ab* and the Ab*–Ag complex were well separated within 4 min, the linear range and the detection limit (S/N = 3) for AFP were 5–500 ng/ml and 0.85 ng/ml (1.2 × 10 −11 M), respectively. The proposed method has been applied satisfactorily in the analysis of human sera samples.

Catena-Poly[[[triaqua(4,4′-bipyridineN,N′-dioxide-κO)dichloridocerium(III)]-μ2-4,4′-bipyridineN,N′-dioxide-κ2O:O′] chloride monohydrate

In the title compound, [CeCl2(C10H8N2O2)2(H2O)3]Cl·H2O, each CeIII atom is coordinated by six O atoms [Ce—O = 2.454 (3)–2.454 (3) Å] and two chloride ions [Ce—Cl = 2.8277 (9) and 2.8721 (9) Å] in a distorted tetra­gonal-anti­prismatic geometry. One of the 4,4′-bipyridine N,N′-dioxide ligands acts as a bridging ligand while the other acts a terminal ligand, leading to the formation of a linear polymeric structure. In the crystal structure, adjacent polymeric chains are cross-linked by O—H⋯O and O—H⋯Cl hydrogen bonds, forming a three-dimensional network.

Simultaneous determination of benserazide and levodopa by capillary electrophoresis–chemiluminescence using an improved interface

A capillary electrophoresis coupling with indirect chemiluminescence detection method for the simultaneous determination of benserazide and levodopa has been developed. The detection interface was improved to simplify the capillary electrophoresis–chemiluminescence (CE–CL) system and the features of this improved interface were illustrated in this paper. The CE–CL conditions for the simultaneous determination of benserazide and levodopa were optimized. Under the optimal conditions, the CL intensity was linear with concentrations of levodopa in the range of 1.0 to 100.0 μg ml −1, and benserazide in the range of 10.0 to 1000 μg ml −1, respectively. The detection limits (S/N = 3) in turn were 1.85 μg ml −1 for BS and 0.12 μg ml −1 for L-dopa with relative standard deviations of less than 3%. The proposed method has been successfully applied to the determination of benserazide and levodopa in medopar tablets and spiked urine samples, demonstrating the feasibility and reliability of the proposed method.

Role of cerium in promoting the stability of CuHM catalyst against HCl to reduce NO with NH 3

To enhance the chlorine tolerance of copper ion exchanged mordenite (CuHM) catalyst under NH 3-SCR reaction condition when HCl exists in the feed gas stream, mainly from a waste incinerator, a second metal, particularly cerium, has been additionally exchanged onto the catalyst along with Cu. It prevents Cu(II) ion from being evaporated from the catalyst surface by HCl and significantly improves the catalyst deactivation. The loss of copper from CeCuHM catalyst has been observed at a reaction temperature of 450 °C, while that from CuHM catalyst without Ce begins at 350 °C. Ce simply stabilizes Cu(II) ion on the catalyst surface, generally recognized as an active reaction site for the present reaction system. X-ray absorption near edge spectroscopy (XANES), extended X-ray absorption fine structure (EXAFS), synchrotron radiation X-ray diffraction (SR-XRD), and X-ray photoelectron spectroscopy (XPS) have been employed to identify the stabilization of Cu(II) ion on CuHM catalyst by Ce. As confirmed by SR-XRD, the lattice parameters of the unit cell of CeCuHM catalyst are less altered than those of CuHM catalyst without Ce during the course of the catalyst deactivation. Similarly, as identified by XPS, Cu(II) on the surface of CeCuHM catalyst is less transformed to Cu(I) ions. Ce ions and Ce–Cl compounds formed on the catalyst surface may decrease the average electronegativity of the catalyst and increase the charge of the lattice oxygen in the zeolite framework, resulting in an enhancement of the stability of the Cu–O bond in the present catalytic system.