The structures, electronic and magnetic properties of the FemOn@Cx (m?=?1–3, n?=?1–4, x?=?50, 60) clusters have been investigated by using PBE functional. The C50, C60 can significantly increase the structural stabilities of the FemOn molecules. Fe2O3@C50 and Fe3O4@C50 are more chemically stable than the Fe2O3@C60 and Fe3O4@C60 while FeO@C60 is more chemically stable than the FeO@C50. The spin densities of the FemOn fragments degenerate to zero. Carbon encapsulation leads to the internal charges of the FemOn fragments transfer from 4 s to 4p orbital.
Density functional theory calculations are performed to analyze the structure and stability of Cu and Cu-K clusters with 3 to 9 atoms. The results indicate that the stability of the clusters decreases after doping with a K atom. With the increase of cluster size, the stability of the clusters shows odd-even alternation. Cu8 and Cu7K clusters exhibit the highest stability. Next, different adsorption sites are considered to investigate the geometry of CunNO and Cun−1KNO clusters. By calculating the adsorption energy and the HOMO-LUMO energy gap, it is determined that both types of reactions are exothermic processes, indicating stable adsorption of NO. Notably, the CunK clusters are more active (stronger adsorption) for NO than the Cun clusters. The most chemically active clusters among CunNO and Cun−1KNO clusters are Cu8NO and Cu7KNO clusters. Finally, electron transfer and Mayer bond order analysis of Cu8NO and Cu7KNO clusters reveal that the N O bond order decreases due to electron transfer when Cu/Cu-K clusters adsorb NO. In this process, the N atom is the electron donor and the Cu atom is the electron acceptor. Fundamental insights obtained in this study can be useful in the design of Cu/Cu-K catalysts. 相似文献
In this review are classified and analyzed structural parameters of almost 90 monomeric organoplatinum complexes with inner coordination spheres consisting of PtPCOX (X?=?N, Cl, S), PtPCNX (X?=?Cl, S, Br, I, As) and PtPCClX (X?=?S, I, As). These complexes crystallized in three crystal systems: orthorhombic (× 11), triclinic (× 32) and monoclinic (× 45). Distorted square planar arrangements about the Pt(II) atoms are provided by mono-, heterobi- and heterotridentate donor ligands. The chelating ligands create a wide variety of four-, five- and six-membered metallocyclic rings and the effects of both steric and electronic factors influence the L–Pt–L bite angles. There are wide variations in the trans-positions of the donor ligands. Two examples are classified as distortion isomers. 相似文献
Driven by the goal of establishing a fossil-fuel-free and nuclear-power-free economy based on renewable energy, metal-air batteries are regarded as promising energy conversion and storage devices. Developing efficient oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) bifunctional electrocatalysts for the air electrode of metal-air batteries is becoming increasingly important. In this work, 36 transition metal (TM) single-atom catalysts are designed based on MXenes Ti2CT2 with different surface terminal atoms (T = O, S, Cl), and their ORR/OER catalytic activity and stability are evaluated by the density functional theory. Ni@Ti2CO2, Pd@Ti2CS2, and Co@Ti2CCl2 are found to exhibit good catalytic activity with ORR/OER overpotentials of .54 V/.62 V, .59 V/.29 V, .44 V/.40 V. The aggregation behavior of three catalysts is estimated by comparing the average binding energy of one, two, three, and four TM atoms anchored on Ti2CT2. This work cannot only provide a theoretical guide to develop bifunctional single-atom catalysts, but also help us understand the effect of terminal atoms on the electronic structures and catalytic activity of TM@Ti2CT2. 相似文献
La1-xAxCoO3-δ (A = Sr, Ba) nanoparticles used as an inert anode in molten salts were characterized using phonon vibrations, and their compositions and morphologies were investigated. These nanoparticles were used for nanostructure fabrication of an inert anode to reduce oxide ion transportation. The singularity structure changes with increasing Sr ion content in La1-xSrxCoO3-δ nanoparticles showed a transient of spin state change from a low-spin state to intermediate- and/or high-spin states. The valencies of Co ion in La1-xSrxCoO3-δ were 3.2 and 3.3 for La0.8Sr0.2CoO3-δ and La0.6Sr0.4CoO3-δ, respectively, suggesting that oxygen defects were introduced by Sr ion doping in La1-xSrxCoO3-δ nanoparticles. In contrast, the valencies of Co ion in La1-xBaxCoO3-δ were 3.1 and 3.0 for La0.5Ba0.5CoO3-δ and La0.4Ba0.6CoO3-δ, respectively, suggesting that oxygen defects were introduced slightly by Ba ion doping in La1-xBaxCoO3-δ nanoparticles. The isotropic phonon vibrations of La1-xAxCoO3-δ nanoparticles were estimated using high-temperature synchrotron radiation X-ray diffraction measurements. Crystal anisotropy measurements of phonon vibrations indicated that the oxide ions diffused preferentially along the (a, b) plane in the La1-xSrxCoO3-δ crystal lattice and toward the c-axis direction in the La1-xBaxCoO3-δ crystal lattice. These results suggest that the oxide ion transportation was curtailed using layered nanoparticles to fabricate an inert anode.
Structural Chemistry - A new type of halogen bond formed by supermetals or superalkalies with dihalogen molecules was analyzed by means of ab initio at the MP2/aug-cc-pVTZ level. The results reveal... 相似文献
The total synthesis of the mycobacterial toxins mycolactones A/B ( 1 a / b ) has been accomplished based on a strategy built around the construction of the mycolactone core through ring‐closing metathesis. By employing the Grubbs second‐generation catalyst, the 12‐membered core macrocycle of mycolactones, with a functionalized C2 handle attached to C11, was obtained in 60–80 % yield. The C‐linked upper side chain (comprising C12–C20) was completed by a highly efficient modified Suzuki coupling between C13 and C14, while the attachment of the C5‐O‐linked polyunsaturated acyl side chain was achieved by Yamaguchi esterification. Surprisingly, a diene containing a simple isopropyl group attached to C11 could not be induced to undergo ring‐closing metathesis. By employing fluorescence microscopy and flow cytometry techniques, the synthetic mycolactones A/B ( 1 a / b ) were demonstrated to display similar apoptosis‐inducing and cytopathic effects as mycolactones A/B extracted from Mycobacterium ulcerans. In contrast, a simplified analogue with truncated upper and lower side chains was found to be inactive. 相似文献
We investigated the magnetic and thermoelectric properties of REMoN3 (RE = La, Ce, Pr, Nd, Sm) perovskites using the full potential linearized augmented plane wave (FP-LAPW) method. To overcome the problem of underestimation of electronic interaction, we employed the DFT + U approach to accurately map the electronic structure of these compounds. Our study shows an increasing trend in the magnetic moments with the increasing number of unpaired electrons in RE. Among these compounds, SmMoN3 possesses a large magnetic moment, which is suitable for applications such as memory devices and sensors. Interestingly, all these perovskites display ferromagnetic behavior except CeMoN3, which exhibits an antiferromagnetic nature. Furthermore, our analysis indicates n-type thermoelectric behavior in all these materials. The compound, namely PrMoN3, exhibits a high figure of merit among REMoN3, which can be improved by modifying the lattice sites. 相似文献
Four new heterobimetallic complexes [CuL1][MnCl4] (1), [CuL2][MnCl4] (2), [NiL1][MnCl4] (3), [NiL2][MnCl4] (4) (L1?=?4,6,6-trimethyl-1,9-diamino-3,7-di-aza-nona-3-ene; L2?=?1,15-dihydroxy-7,9,9-trimethyl-3,6,10,13-tetra-aza-pentadeca-6-ene) have been prepared from elemental metals, ethylenediamine dihydrochloride or its N-(2-hydroxyethyl) derivative and acetone by the template condensation reaction. All complexes have been characterized by elemental analysis, IR and UV-Visible spectroscopy. The structures of 2 and 3 have been determined by X-ray crystallography (2: Orthorhombic, Pna21, a?=?20.136(4), b?=?11.185(2), c?=?10.251(2)Å, Z?=?4; 3: Orthorhombic, Pca21, a?=?14.335(2), b?=?11.405(2), c?=?11.154(2)Å, Z?=?4 ). Both crystals consist of alternating complex cations [ML]2+ and anions [MnCl4]2? linked together by N–H···Cl–Mn and O–H···Cl–Mn hydrogen bonds forming 2D corrugated sheets in (2) and 1D helical chains in (3). Complex 2 represents the first single crystal structure elucidation of the complex containing L2. 相似文献
This article details the development of a novel method that overcomes the drawbacks of sandwich ELISA (sELISA) and allows
reliable evaluation of simultaneous quantification of the amyloid (Aβ)-peptides, total-Aβ, Aβx-38, Aβx-40, and Aβx-42, in
rat brain by optimized sample purification and column-switching liquid chromatographic-tandem mass spectrometry (LC/MS/MS).
This method provides accurate analyses of total-Aβ, Aβx-38, Aβx-40, and Aβx-42 with a linear calibration range between 0.05
and 45 ng/mL. Verification for accuracy and precision of biological samples were determined by a standard addition and recovery
test, spiked with synthetic Aβ1-38, Aβ1-40, and Aβ1-42 into the rat brain homogenate. This method showed <20% relative error
and relative standard deviation, indicating high reproducibility and reliability. The brain concentrations of total-Aβ, Aβx-38,
Aβx-40, and Aβx-42 after oral administration of flurbiprofen in rats were measured by this method. Aβx-42 concentrations (4.57 ± 0.69 ng/g)
in rats administered flurbiprofen were lower than those in untreated rats (6.48 ± 0.93 ng/g). This was consistent with several
reports demonstrating that NSAIDs reduced the generation of Aβ. We report here a method that allows not only the quantification
of specific molecular species of Aβ but also simultaneous quantification of total-Aβ, Aβx-38, Aβx-40, and Aβx-42, thus overcoming
the drawbacks of sELISA. 相似文献
Black phosphorus (BP) is a desirable anode material for alkali metal ion storage owing to its high electronic/ionic conductivity and theoretical capacity. In-depth understanding of the redox reactions between BP and the alkali metal ions is key to reveal the potential and limitations of BP, and thus to guide the design of BP-based composites for high-performance alkali metal ion batteries. Comparative studies of the electrochemical reactions of Li+, Na+, and K+ with BP were performed. Ex situ X-ray absorption near-edge spectroscopy combined with theoretical calculation reveal the lowest utilization of BP for K+ storage than for Na+ and Li+, which is ascribed to the highest formation energy and the lowest ion diffusion coefficient of the final potassiation product K3P, compared with Li3P and Na3P. As a result, restricting the formation of K3P by limiting the discharge voltage achieves a gravimetric capacity of 1300 mAh g−1 which retains at 600 mAh g−1 after 50 cycles at 0.25 A g−1. 相似文献
In situ atomic force microscopy (AFM) allows images from the upper face and sides of TCNQ crystals to be monitored during
the course of the electrochemical solid–solid state conversion of 50 × 50 μm2 three-dimensional drop cast crystals of TCNQ to CuTCNQ or M[TCNQ]2(H2O)2 (M = Co, Ni). Ex situ images obtained by scanning electron microscopy (SEM) also allow the bottom face of the TCNQ crystals,
in contact with the indium tin oxide or gold electrode surface and aqueous metal electrolyte solution, to be examined. Results
show that by carefully controlling the reaction conditions, nearly mono-dispersed, rod-like phase I CuTCNQ or M[TCNQ]2(H2O)2 can be achieved on all faces. However, CuTCNQ has two different phases, and the transformation of rod-like phase 1 to rhombic-like
phase 2 achieved under conditions of cyclic voltammetry was monitored in situ by AFM. The similarity of in situ AFM results
with ex situ SEM studies accomplished previously implies that the morphology of the samples remains unchanged when the solvent
environment is removed. In the process of crystal transformation, the triple phase solid∣electrode∣electrolyte junction is
confirmed to be the initial nucleation site. Raman spectra and AFM images suggest that 100% interconversion is not always
achieved, even after extended electrolysis of large 50 × 50 μm2 TCNQ crystals. 相似文献
The quasi-classical trajectory calculations for O(1D)?+?HCl?→?OH?+?Cl (R1) and O(1D)?+?HCl?→?ClO?+?H (R2) reactions have been performed at hyperthermal collision energies (60.0, 90.0, and 120.0 kal/mol) on the 1A' state. Reaction probabilities and integral cross sections are calculated. The product rotational distributions for the two channels, and the product rotational alignment parameters are investigated. Also, the alignment and the orientation of the products have been predicted through the angular distribution functions (concerning the initial/final velocity vector, and the product rotational angular momentum vector). To have a deeper understanding of the natures of the vector correlation between reagent and product relative velocities, a natural generalization of the differential cross section __PDDCS00, is calculated.
Results
The OH?+?Cl channel is the main product channel and is observed to have essentially isotropic rotational distributions. The ClO?+?H channel is found to be clearly rotationally polarized.
Conclusions
The dynamical, especially the stereodynamical characters are quite different for the two channels of the title reaction. Most reactions occur directly, except for R2 reaction at the collision energies of 60.0 and 120.0 kcal/mol. The alignment and orientation effects are weak/strong for R1/R2 reaction. The well structure on the potential energy surface and hyperthermal collision energies might result in the dynamical effects.