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1.
2.
Yu-Ning Chang 《Inorganica chimica acta》2007,360(1):136-142
The coordination chemistry of a potentially tridentate, dianionic biphenolato phosphine ligand with respect to group 1 metals is described. Deprotonation of bis-(3,5-di-tert-butyl-2-hydroxyphenyl)phenylphosphine (H2[OPO]) with two equivalents of n-BuLi, NaH, or KH in dimethoxyethane (DME) solutions produces the corresponding dinuclear alkali metal complexes [OPO]M2(DME)2 (M = Li, Na, K). The X-ray structure of [OPO]Li2(DME)2 reveals that the two lithium atoms are bridged by both phenolato oxygen donors with only one lithium being coordinated to the phosphorus donor. Consistently, variable-temperature 31P{1H} and 7Li{1H} NMR spectroscopic studies elucidate the coordination of the phosphorus donor in [OPO]Li2(DME)2 to one of the lithium atoms in solution. Interestingly, an X-ray diffraction study of the potassium complex indicates a dimeric structure with S2 symmetry for this species in which the four potassium atoms are bridged by both phosphorus and oxygen donors of the biphenolato phosphine ligands. These alkali metal complexes are active initiators for catalytic ring-opening polymerization of ε-caprolactone. 相似文献
3.
Weibo Hua Mingzhe Chen Bjrn Schwarz Michael Knapp Michael Bruns Juri Barthel Xiushan Yang Florian Sigel Raheleh Azmi Anatoliy Senyshyn Alkesandr Missiul Laura Simonelli Martin Etter Suning Wang Xiaoke Mu Andy Fiedler Joachim R. Binder Xiaodong Guo Shulei Chou Benhe Zhong Sylvio Indris Helmut Ehrenberg 《Liver Transplantation》2019,9(8)
As promising cathode materials, the lithium‐excess 3d‐transition‐metal layered oxides can deliver much higher capacities (>250 mAh g?1 at 0.1 C) than the current commercial layered oxide materials (≈180 mAh g?1 at 0.1 C) used in lithium ion batteries. Unfortunately, the original formation mechanism of these layered oxides during synthesis is not completely elucidated, that is, how is lithium and oxygen inserted into the matrix structure of the precursor during lithiation reaction? Here, a promising and practical method, a coprecipitation route followed by a microwave heating process, for controllable synthesis of cobalt‐free lithium‐excess layered compounds is reported. A series of the consistent results unambiguously confirms that oxygen atoms are successively incorporated into the precursor obtained by a coprecipitation process to maintain electroneutrality and to provide the coordination sites for inserted Li ions and transition metal cations via a high‐temperature lithiation. It is found that the electrochemical performances of the cathode materials are strongly related to the phase composition and preparation procedure. The monoclinic layered Li[Li0.2Ni0.2Mn0.6]O2 cathode materials with state‐of‐the‐art electrochemical performance and comparably high discharge capacities of 171 mAh g?1 at 10 C are obtained by microwave annealing at 750 °C for 2 h. 相似文献
4.
The preparation and characterization of organolithium O,C,O-pincer compound [2,6-(tBuOCH2)2C6H3]-Li (1) is described. The X-ray diffraction techniques revealed the dimeric structure of 1 consisting of two lithium atoms Li(1) and Li(2) and two monoanionic chelating aryl ligands in the solid state, where each lithium atom is coordinated by two oxygen atoms of two different ligands. The NMR spectroscopy and cryoscopy measurements established monomer-dimer equilibrium of 1 in concentrated solutions of non-coordinated solvents, while the diluted solutions of 1 consist of monomer only. 相似文献
5.
A. A. Tulub 《Biophysics》2008,53(5):371-377
The molecular dynamics method (density functional theory) DFT:B3LYP (6-3IG** basis set, t = 310 K) was used to study interactions between a molecule of adenosinetriphosphate (ATP) (ATP subsystem) and the [Mg(H2O)6]2+ magnesium cofactor (Mg subsystem) in an aqueous medium simulated by 78 water molecules in the singlet (S) and triplet (T) states. Potential energy surfaces (PESs) for the S (lowest in energy) and T states (highest in energy) are significantly separated in space. Motion along them directs the Mg complex either to oxygen atoms of the γ-β-phosphate groups (O1–O2) (S state of PES) or to oxygen atoms of the β-α-phosphate groups (O2–O3) (T state of PES). Chelation of the γ-β- and β-α-phosphates leads to formation of a stable low-energy ([Mg(H2O)4-(OI-O2)ATP]2?) complex or a metastable high-energy ([Mg(H2O)2-(O2–O3)ATP]2?) complex, respectively, which differ in number of water molecules surrounding the Mg atom. Intersection of two T PESs is accompanied by formation of an unstable state characterized by redistribution of spins between the Mg and ATP subsystems. This state, being sensitive to interaction with the Mg nuclear spin (25Mg), induces an unpaired electron spin, which initiates the ATP cleavage by the ion-radical mechanism, yielding a reactive ion radical of adenosinemonophosphate (·AMP?), which was earlier found experimentally by the method of chemically induced dynamic nuclear polarization (CIDNP). Biological aspects of the results obtained are discussed. 相似文献
6.
Menyhárd DK 《Bioorganic & medicinal chemistry letters》2011,21(12):3523-3526
H-NOX proteins are at present the only structural models available for the study of the ligand binding affinity and selectivity of soluble guanylate cyclase, the physiological receptor of nitric oxide. The oxy complex and resting state structures of two bacterial H-NOX proteins of markedly different oxygen affinity, but of quite similar sequence, were studied by molecular dynamics simulations at 300 K and 400 K. Unexpectedly, the different O2 affinity was found to be reflected in differences of the resting states structures. A conformation containing a pre-formed oxygen-binding cage is the most populated in the resting state equilibrium ensemble of the only successful O2 binder, Tt H-NOX at 300 K, suggesting that conformational selection governs the interaction. 相似文献
7.
X-Ray data collected at 87 K showed crystals of sodium α-l-guluronate dihydrate (C6H9O7Na · 2 H2O) to be orthorhombic, P212121 with a = 7.591(2), b = 18.884(5), c = 6.842(2) Å, and Z = 4. The structure was solved by direct methods, and full-matrix least-squares refinement based on 1587 Fo yielded R = 0.043 and Rw = 0.033. The structure analysis indicates partial anomeric disorder with α:β ~90:10. The guluronate ring has the 1C4(l) conformation. Sodium binds two translation-equivalent guluronate units and one water molecule in a primary five-fold coordination. The complexing oxygen functions, which include all axial hydroxyl groups and one carboxylate oxygen atom in the guluronate ring, describe a distorted trigonal bipyramid. A prominent feature of the crystal structure is the stacks of sodium atoms and guluronate residues in alternating sequence along the c axis. The stacks are held together by an intricate system of hydrogen bonds involving all oxygen atoms in the structure. The water molecules play an important role in this system both as hydrogen donors and acceptors. 相似文献
8.
Z. Du R. Grau-Crespo P. B. Wilson J. P. Brodholt M. Calleja 《Molecular simulation》2013,39(5):339-347
Computer modelling techniques were used to investigate the structures and stabilities of Li–K solid solutions of three different disilicate structures, employing a newly developed program based on symmetry arguments to identify identical configurations and hence eliminate unnecessary duplication of calculations. Even so, the large number of calculations needed to sample the complete set of configurations of a wide range of solid solutions necessitated the use of an extensive Condor pool of PC clusters, which afforded the necessary computing resources for this study. The results of our calculations show that in the wide range of Li–K solid solutions investigated, the mixed-cationic KLiSi2O5 material retains its original structure when the composition was varied, where six-membered rings of silica tetrahedra are linked to form continuous channels throughout the structure. The channel positions are found to be preferentially occupied by the potassium ions rather than by the smaller lithium ions. The original framework of the experimental K2Si2O5 structure, containing 14-membered rings of silica tetrahedra, similarly remains intact with the introduction of smaller lithium atoms into the bigger potassium lattice sites. However, the replacement of potassium ions for lithium ions in the Li2Si2O5 material causes significant distortions of the original structure, which loses its symmetry, although the ring structure remains. 相似文献
9.
Operando Lithium Dynamics in the Li‐Rich Layered Oxide Cathode Material via Neutron Diffraction
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Haodong Liu Yan Chen Sunny Hy Ke An Subramanian Venkatachalam Danna Qian Minghao Zhang Ying Shirley Meng 《Liver Transplantation》2016,6(7)
Neutron diffraction under operando battery cycling is used to study the lithium and oxygen dynamics of high Li‐rich Li(Lix/3Ni(3/8‐3x/8)Co(1/4‐x/4)Mn(3/8+7x/24)O2 (x = 0.6, HLR) and low Li‐rich Li(Lix/3Ni(1/3‐x/3)Co(1/3‐x/3)Mn(1/3+x/3)O2 (x = 0.24, LLR) compounds that exhibit different degrees of oxygen activation at high voltage. The measured lattice parameter changes and oxygen position show largely contrasting changes for the two cathodes where the LLR exhibits larger movement of oxygen and lattice contractions in comparison to the HLR that maintains relatively constant lattice parameters and oxygen position during the high voltage plateau until the end of charge. Density functional theory calculations show the presence of oxygen vacancy during the high voltage plateau; changes in the lattice parameters and oxygen position are consistent with experimental observations. Lithium migration kinetics for the Li‐rich material is observed under operando conditions for the first time to reveal the rate of lithium extraction from the lithium layer, and transition metal layer is related to the different charge and discharge characteristics. At the beginning of charging, the lithium extraction predominately occurs within the lithium layer. Once the high voltage plateau is reached, the lithium extraction from the lithium layer slows down and extraction from the transition metal layer evolves at a faster rate. 相似文献
10.
Abstract Molecular dynamics simulation (MD) has been carried out for Li2SiO3 in the molten and glassy states. The parameters of the pair potential functions were determined by a trial and error method so that the results of X-ray diffraction analysis could be well reproduced. The changes in the structure and dynamic properties accompanied by lowering temperature revealed that the glass transition of this simulated system occurred between 973 and 700 K. The ratio of the bridging oxygens to non-bridging oxygens was nearly constant over the investigated temperature range, while a small change in the pattern of branching of the -Si-O-framework was found. The second peaks in the pair correlation functions gSi-O(r) and gSi-Si(r) split at lower temperature. These splittings suggest that the motion changing the relative orientations of two neighboring SiO4 units may be nearly frozen at lower temperature. 相似文献
11.
Sujittra Youngme Pongthipun Phuengphai Gerard A. van Albada Jan Reedijk 《Inorganica chimica acta》2005,358(11):3267-3271
The synthesis, X-ray structure, spectroscopic and magnetic properties of a zig-zag formato-bridged chain complex with the formula [Cu(dpyam)(μ-O2CH)(OH2)]n(NO3)n (1) (in which dpyam = di-2-pyridylamine) is described.The geometry of the copper(II) ion is distorted square pyramidal with a basal plane consisting of two nitrogen atoms of the dpyam ligand (Cu-N distances 1.987(3) and 2.010(3) Å) and two oxygen atoms of two different formato ligands (Cu-O distances 1.974(2) and 1.975(2) Å). A coordinated water molecule occupies the axial position at a distance of 2.222(3) Å. The copper atoms are bridged unsymmetrically by a formato anion in a syn-anti arrangement, resulting in a polymeric zig-zag chain structure.The magnetic susceptibility measurements (5-280 K) agree with a very weak ferromagnetic chain interaction between the Cu centres with a J value of 0.75 cm−1. 相似文献
12.
A tetranuclear copper(II) complex [Cu4(NSI)4] · 2C2H5OH · 2H2O (NSI=hydroxethylsalicydeneimine) has been synthesized and characterized by X-ray diffraction analysis. The compound crystallizes in the monoclinic system, space group P2(1), a=9.494(3) Å, b=18.687(5) Å, c=13.149(4) Å, β=110.162(5)°, Z=2, R1=0.0482 and wR2=0.0978. The crystal structure contains a tetranuclear pseudo-cubane core based on an approximately cubane array of alternating copper and oxygen atoms. Each copper atom resides in a distorted square planar coordination environment with one nitrogen and three oxygen atoms from two NSI ligands. The tetranuclear units are linked in the crystal by O-H?O hydrogen bonds and weak Cu?O co-ordination bonds into one-dimensional structure. Variable temperature (5-300 K) magnetic measurements indicate the existence of ferromagnetic interactions among copper atoms. The IR and ESR spectra have also been investigated. 相似文献
13.
Yanglansen Cui Kefeng Xiao Nicholas M. Bedford Xinxin Lu Jimmy Yun Rose Amal Da‐Wei Wang 《Liver Transplantation》2019,9(37)
Morphological engineering of nanosized transitional metal oxides shows great promise for performance improvement, yet limited efforts have been attempted to engineer the atomic structure. Oxygen vacancy (VO) can boost charge transfer leading to enhanced performance; yet excessive VO may impair the conductivity. Herein, tungsten oxide is atomically tailored by incorporating nitrogen heteroatoms into the oxygen vacancies. The efficient nitrogen‐filling into the oxygen vacancies is evidenced by the electron paramagnetic resonance spectroscopy and X‐ray absorption spectroscopy. The coordinated N atoms play a crucial role in facilitating the charge transfer and maintaining efficient lithium‐ion diffusion. Consequently, the tungsten oxide with N‐filled oxygen vacancies exhibits superior lithium‐ion storage performance. 相似文献
14.
Arthur Pichler Christine Rauch Wolfgang Flader Bernd Wellenzohn Klaus R. Liedl Andreas Hallbrucker 《Journal of biomolecular structure & dynamics》2013,31(4):547-559
Abstract A nonoriented hydrated film of poly(dG-dC) with ≈20 water molecules per nucleotide (called B by Loprete and Hartman (Biochem. 32, 4077–4082 (1993)) was studied by Fourier transform infrared (FT-IR) spectroscopy either as equilibrated sample between 290 and 270 K or, after quenching into the glassy state, as nonequilibrated film isothermally at 200 and 220 K. IR spectral changes on isothermal relaxation at 200 and 220 K, caused by interconversion of two conformer substates, are revealed by difference spectra. Comparison with difference curves obtained in the same manner from two classical B-DNA forms, namely the d(CGCGAATTCGCG)2 dodecamer and polymeric NaDNA from salmon testes, revealed that the spectral changes on BIto-BII interconversion in the classical B-DNA forms are very similar to those in the B-form, and that the spectroscopic differences between the BI and BII features from classical B-DNA and those from the modified B-form are minor. Nonexponential kinetics of the BI→BII transition in the B-form of poly(dG-dC) at 200 K showed that the structural relaxation time is about three times of that in the classical B-DNA forms (≈30 versus ≈10 min at 200 K). The unexpected reversal of conformer substates interconversion (that is BII→BI transition on cooling from 290 K and BI→BII transition on isothermal relaxation at 200 K) observed for classical B-DNA occurs also in the modified B-form. We therefore conclude that restructuring of hydration shells rules the low-temperature dynamics of the B-form via its two conformer substates in the same manner reported for classical B-DNA by Pichler et al. (J. Phys. Chem. B 106, 3263–3274 (2002)). 相似文献
15.
Rui Wang Xiaoqing He Lunhua He Fangwei Wang Ruijuan Xiao Lin Gu Hong Li Liquan Chen 《Liver Transplantation》2013,3(10):1358-1367
Li2MnO3 is the parent compound of the well‐studied Li‐rich Mn‐based cathode materials xLi2MnO3·(1‐x)LiMO2 for high‐energy‐density Li‐ion batteries. Li2MnO3 has a very high theoretical capacity of 458 mA h g?1 for extracting 2 Li. However, the delithiation and lithiation behaviors and the corresponding structure evolution mechanism in both Li2MnO3 and Li‐rich Mn‐based cathode materials are still not very clear. In this research, the atomic structures of Li2MnO3 before and after partial delithiation and re‐lithiation are observed with spherical aberration‐corrected scanning transmission electron microscopy (STEM). All atoms in Li2MnO3 can be visualized directly in annular bright‐field images. It is confirmed accordingly that the lithium can be extracted from the LiMn2 planes and some manganese atoms can migrate into the Li layer after electrochemical delithiation. In addition, the manganese atoms can move reversibly in the (001) plane when ca. 18.6% lithium is extracted and 12.4% lithium is re‐inserted. LiMnO2 domains are also observed in some areas in Li1.63MnO3 at the first cycle. As for the position and occupancy of oxygen, no significant difference is found between Li1.63MnO3 and Li2MnO3. 相似文献
16.
Reduced cerium dioxide (CeO2?x) can reduce water, producing hydrogen at ?298 K. Kinetic studies were focused on the stoichiometric reaction of δ-phase cerium oxide (CeO1.818) with water vapor. Different activation energies of 18.1 and 33.4 kJ mol?1 were observed for the reactions at the temperature ranges above and below ca. 453 K, respectively. Rate equations observed in the two temperature ranges were also different. These results strongly suggest that the rate-determining steps are different between the two temperature ranges. Rapid oxygen exchange observed between H218O and lattice oxygen in cerium oxide of δ- phase at ? 298 K indicated that neither the adsorption of water molecules not the diffusion of oxygen ions in the bulk of the oxide can be the rate-determining step. H2D2 exchange occurred rapidly at 373 K compared to the rate of water decomposition, suggesting that the recombination of hydrogen atoms on the surface is not rate- determining either. A tentative reaction mechanism was proposed to explain the results of the kinetic studies. The rate-determining step at high temperatures (>453 K) is the reduction of OH? by the six-coordinated Ce3+ which is present in the nonstoichiometric cerium oxide, while that at low temperatures (<453 K) is the subsequent reduction of H+ by the seven-coordinated Ce3+. 相似文献
17.
《Liver Transplantation》2018,8(25)
Solid polymer electrolytes (SPEs) promise to improve the safety and performance of lithium ion batteries (LIBs). However, the low ionic conductivity and transference number of conventional poly(ethylene oxide) (PEO)‐based SPEs preclude their widespread implementation. Herein, crosslinked poly(tetrahydrofuran) (xPTHF) is introduced as a promising polymer matrix for “beyond PEO” SPEs. The crosslinking procedure creates thermally stable, mechanically robust membranes for use in LIBs. Molecular dynamics and density functional theory (DFT) simulations accompanied by 7Li NMR measurements show that the lower spatial concentration of oxygen atoms in the xPTHF backbone leads to loosened O–Li+ coordination. This weakened interaction enhances ion transport; xPTHF has a high lithium transference number of 0.53 and higher lithium conductivity than a xPEO SPE of the same length at room temperature. It is demonstrated that organic additives further weaken the O–Li+ interaction, enabling room temperature ionic conductivity of 1.2 × 10−4 S cm−1 with 18 wt% N,N‐dimethylformamide in xPTHF. In a solid‐state LIB application, neat xPTHF SPEs cycle with near theoretical capacity for 100 cycles at 70 °C, with rate capability up to 1 C. The plasticized xPTHF SPEs operate at room temperature while maintaining respectable rate capability and capacity. The novel PTHF system demonstrated here represents an exciting platform for future studies involving SPEs. 相似文献
18.
Yu. A. Mankelevich A. F. Pal’ N. A. Popov T. V. Rakhimova A. V. Filippov 《Plasma Physics Reports》2001,27(11):979-989
The current dynamics in a non-self-sustained glow discharge in atmospheric-pressure nitrogen (with a small admixture of oxygen) at cryogenic and room temperatures is studied experimentally and theoretically. For the first time, the theoretical model incorporates the processes of the decomposition of O 2 + ·N2 and NO+·N2 complex ions in collisions with vibrationally excited nitrogen molecules and the associative ionization reactions with the participation of excited nitrogen and oxygen atoms. The computation results agree quite satisfactorily with the experimental data on the current dynamics and the duration of the stable phase of a non-self-sustained discharge for various applied voltages. Even a small (0.01%) oxygen admixture is found to greatly affect the dynamics of the ion composition and the characteristic duration of the stable phase of a non-self-sustained discharge in atmospheric-pressure nitrogen. 相似文献
19.
Maurício Cavicchioli Antonio Carlos Massabni Lilian P.B. Sabeh 《Inorganica chimica acta》2007,360(9):3055-3060
Synthesis and X-ray structure of a dinuclear platinum(II) complex with the ligand saccharin(sac) are described. The structure shows two approximately square-planar platinum centers. Each platinum atom is coordinated to one water molecule and three N-bonded saccharinate ligands. The two centers are linked through two potassium atoms. Each potassium atom interacts with six oxygen atoms from hydration and coordinated water molecules and from carbonyl and sulfonate groups of the ligands. It is suggested that, in aqueous solution, the dimeric structure of the complex is dissociated and the monomeric species K[Pt(sac)3(H2O)] is formed. The complex was dissolved in water and submitted to in vitro cytotoxic analyses using HeLa cells (human cervix cancer). It was shown that the monomeric complex elicited a potent cytotoxic activity when compared to the vehicle-treated cells. The IC50 value for the monomeric complex is 6.8 μM, a little bit higher than that obtained for cisplatin. 相似文献
20.
Two novel coordination polymeric complexes [Co(pzca)2(H2O)]n (1) and [Mn(pzca)2]n (2) (pzca=2-pyrazinecarboxylate) have been synthesized by hydrothermal reaction of M(CH3COO)2·4H2O (M=Co, Mn) and 2-pyrazinecarboxylic acid. The complex 1 displays an infinite zigzag chain structure in which each cobalt(II) center was coordinated by three nitrogen and three oxygen atoms to generate a CoN3O3 octahedral geometry. The existence of hydrogen bond leads to the formation of the interpenetrating stacking structure. Complex 2 indicates a two-dimensional layer structure through the linkage of bridging oxygen atom of pzca ligand. Each Mn(II) center exhibits a distorted octahedral coordination environment with four oxygen atoms and two nitrogen atoms. The distances of adjacent Mn(II) atoms are 3.503 and 5.654 Å, respectively. The magnetic property analyses reveal that both complexes show weak antiferromagnetic exchange interactions between the metal centers. 相似文献