Synthesis, composition, and structure of sillenite-type solid solutions in the Bi2O3-SiO2-MnO2 system

Individual compounds and solid solutions are obtained under hydrothermal conditions in the Bi(2)O(3)-SiO(2)-MnO(2) system in the form of faceted crystals and epitaxial films on the Bi(24)Si(2)O(40) substrate. The crystals have the shape of a cube (for the molar ratio of the starting components Na(2)SiO(3)·9H(2)O:Mn(NO(3))(2)·6H(2)O > 1), a tetrahedron (for Na(2)SiO(3)·9H(2)O:Mn(NO(3))(2)·6H(2)O < 1), or a tetrahedron-cube combination (for Na(2)SiO(3)·9H(2)O:Mn(NO(3))(2)·6H(2)O = 1). Crystal-chemical analysis based on the data of single-crystal and powder X-ray diffraction, IR spectra, and the results of calculation of the local balance by the bond-valence method reveals formation of the Bi(24)(Si(4+),Mn(4+))(2)O(40) phases, which probably include Mn(5+) ions (epitaxial films), as well as the Bi(24)(Si(4+),Bi(3+),Mn(4+))(2)O(40) and Bi(24)(Si(4+),Mn(4+))(2)O(40) phases in the (1 - x)Bi(3+)(24)Si(4+)(2)O(40) - x(Bi(3+)(24)Mn(4+)(2)O(40)) system and the Bi(24)(Bi(3+),Mn(4+))(2)O(40) phase in the (1 - x)Bi(3+)(24)Bi(3+)(2)(O(39)?(1)) - x(Bi(3+)(24)Mn(4+)(2)O(40)) system. Precision X-ray diffraction studies of single crystals of the Bi(24)(Bi,Si,Mn)(2)O(40) general composition show that these sillenites crystallize in space group P23 and not I23 as the Bi(24)Si(2)O(40) phase. The dissymmetrization of sillenite phases is observed for the first time. It is explained by a kinetic (growth) phase transition of the order-disorder type due to population of a crystallographic site by atoms with different crystal-chemical properties and quasi-equilibrium conditions of crystal growth in the course of a hydrothermal synthesis below 400 °C at unequal molar amounts of the starting components in the batch.     

Synthetic entry into polynuclear bismuth-manganese chemistry: high oxidation state Bi(III)2Mn(IV)6 and Bi(III)Mn(III)10 complexes

The first high nuclearity, mixed-metal Bi(III)/Mn(IV) and Bi(III)/Mn(III) complexes are reported. The former complexes are [Bi(2)Mn(IV)(6)O(9)(O(2)CEt)(9)(HO(2)CEt)(NO(3))(3)] (1) and [Bi(2)Mn(IV)(6)O(9)(O(2)CPh)(9)(HO(2)CPh)(NO(3))(3)] (2) and were obtained from the comproportionation reaction between Mn(O(2)CR)(2) and MnO(4)(-) in a 10:3 ratio in the presence of Bi(NO(3))(3) (3 equiv) in either a H(2)O/EtCO(2)H (1) or MeCN/PhCO(2)H (2) solvent medium. The same reaction that gives 2, but with Bi(O(2)CMe)(3) and MeNO(2) in place of Bi(NO(3))(3) and MeCN, gave the lower oxidation state product [BiMn(III)(10)O(8)(O(2)CPh)(17)(HO(2)CPh)(H(2)O)] (3). Complexes 1 and 2 are near-isostructural and possess an unusual and high symmetry core topology consisting of a Mn(IV)(6) wheel with two central Bi(III) atoms capping the wheel on each side. In contrast, the [BiMn(III)(10)O(8)](17+) core of 3 is low symmetry, comprising a [BiMn(3)(μ(3)-O)(2)](8+) butterfly unit, four [BiMn(3)(μ(4)-O)](10+) tetrahedra, and two [BiMn(2)(μ(3)-O)](7+) triangles all fused together by sharing common Mn and Bi vertices. Variable-temperature, solid-state dc and ac magnetization data on 1-3 in the 1.8-300 K range revealed that 1 and 2 possess an S = 0 ground state spin, whereas 3 possesses an S = 2 ground state. The work offers the possibility of access to molecular analogs of the multifunctional Bi/Mn/O solids that are of such great interest in materials science.     

Designed ferromagnetic, ferroelectric Bi(2)NiMnO(6)

A newly designed ferromagnetic, ferroelectric compound, Bi(2)NiMnO(6), was prepared by high-pressure synthesis at 6 GPa. The crystal structure, as determined by synchrotron X-ray powder diffraction, is a heavily distorted double perovskite with Ni(2+) and Mn(4+) ions ordered in a rock-salt configuration. The presence of 6s(2) lone pairs of Bi(3+) ions and the covalent Bi-O bonds give ferroelectric properties with T(CE) of 485 K, while -Ni(2+)-O-Mn(4+)-O-Ni(2+)- magnetic paths lead to a ferromagnetism with T(CM) of 140 K. This simple material design to distribute two magnetic elements with and without e(g) electrons on B sites of Bi- and Pb-based perovkites can be applied to other Bi(2)M(2+)M'(4+)O(6) and Pb(2)M(3+)M'(5+)O(6) systems to search for newer ferromagnetic ferroelectrics.     

Syntheses, structures, and magnetic properties of a family of tetra-, hexa-, and nonanuclear Mn/Ni heterometallic clusters

A family of Mn(III)/Ni(II) heterometallic clusters, [Mn(III)(4)Ni(II)(5)(OH)(4)(hmcH)(4)(pao)(8)Cl(2)]·5DMF (1·5DMF), [Mn(III)(3)Ni(II)(6)(N(3))(2)(pao)(10)(hmcH)(2)(OH)(4)]Br·2MeOH·9H(2)O (2·2MeOH·9H(2)O), [Mn(III)Ni(II)(5)(N(3))(4)(pao)(6)(paoH)(2)(OH)(2)](ClO(4))·MeOH·3H(2)O (3·MeOH·3H(2)O), and [Mn(III)(2)Ni(II)(2)(hmcH)(2)(pao)(4)(OMe)(2)(MeOH)(2)]·2H(2)O·6MeOH (4·2H(2)O·6MeOH) [paoH = pyridine-2-aldoxime, hmcH(3) = 2, 6-Bis(hydroxymethyl)-p-cresol], has been prepared by reactions of Mn(II) salts with [Ni(paoH)(2)Cl(2)], hmcH(3), and NEt(3) in the presence or absence of NaN(3) and characterized. Complex 1 has a Mn(III)(4)Ni(II)(5) topology which can be described as two corner-sharing [Mn(2)Ni(2)O(2)] butterfly units bridged to an outer Mn atom and a Ni atom through alkoxide groups. Complex 2 has a Mn(III)(3)Ni(II)(6) topology that is similar to that of 1 but with two corner-sharing [Mn(2)Ni(2)O(2)] units of 1 replaced with [Mn(3)NiO(2)] and [MnNi(3)O(2)] units as well as the outer Mn atom of 1 substituted by a Ni atom. 1 and 2 represent the largest 3d heterometal/oxime clusters and the biggest Mn(III)Ni(II) clusters discovered to date. Complex 3 possesses a [MnNi(5)(μ-N(3))(2)(μ-OH)(2)](9+) core, whose topology is observed for the first time in a discrete molecule. Careful examination of the structures of 1-3 indicates that the Mn/Ni ratios of the complexes are likely associated with the presence of the different coligands hmcH(2-) and/or N(3)(-). Complex 4 has a Mn(III)(2)Ni(II)(2) defective double-cubane topology. Variable-temperature, solid-state dc and ac magnetization studies were carried out on complexes 1-4. Fitting of the obtained M/(Nμ(B)) vs H/T data gave S = 5, g = 1.94, and D = -0.38 cm(-1) for 1 and S = 3, g = 2.05, and D = -0.86 cm(-1) for 3. The ground state for 2 was determined from ac data, which indicated an S = 5 ground state. For 4, the pairwise exchange interactions were determined by fitting the susceptibility data vs T based on a 3-J model. Complex 1 exhibits out-of-phase ac susceptibility signals, indicating it may be a SMM.     

Mullite-derivative Bi2Mn(x)Al(7-x)O14 (x~1): structure determination by powder X-ray diffraction from a multi-phase sample

As a supplementary method to single crystal X-ray diffraction (XRD), nowadays crystal structure determination by powder XRD has become popular, especially for those areas with difficulties getting high quality single crystals. Here we observed an intermediate phase Bi(2)Mn(x)Al(7-x)O(14) (x~1) during the decomposition of mullite-Bi(2)Mn(x)Al(4-x)O(9+δ) (solid solution of Bi(2)Mn(4)O(10)-Bi(2)Al(4)O(9)). As a metastable phase, it started to decompose while forming, thus no single-phase sample can be obtained. We successfully determined its structure by powder XRD from a multi-phase sample. A modified Le Bail fitting using the atomic structure information of known impurities showed a more reliable intensity extraction from a multi-phase powder XRD than that without using atomic structures for the known impurities. The charge-flipping algorithm and Monte-Carlo based simulated annealing technique were then applied to obtain the full structural model. In principle, this strategy is applicable to more complex problems, and not limited to the oxide materials. Bi(2)Mn(x)Al(7-x)O(14) possesses a mullite-related structure. There are one tetrahedral and two octahedral sites for Mn and Al, where disordering with substantial site preferences is observed. Specifically, M1O(6) and M3O(6) octahedra share edges along the c-direction with the periodicity of 1 : 2. These octahedral chains are further connected into a 3D structure through M2O(4) dimmers and Bi.     

Heteroatomic deltahedral clusters: synthesis and structures of closo-[Bi3Ni(4)(CO)6]3-, closo-[Bi4Ni4(CO)6]2-, the open cluster [Bi3Ni6(CO)9]3-, and the intermetalloid closo-[Nix@[Bi6Ni6(CO)8)]4-

Reactions of ethylenediamine solutions of K4Bi5 with Ni(PPh3)2(CO)2 yielded four novel hetero-atomic Bi/Ni deltahedral clusters. Three of them, the 7-atom pentagonal bipyramidal [Bi3Ni4(CO)6]3-, the 8-atom dodecahedral [Bi4Ni4(CO)6]2-, and the Ni-centered or empty 12-atom icosahedral [Nix@[Bi6Ni6(CO)8]4-, are closo-species according to both electron count and shape. The centered icosahedral cluster resembles packing in intermetallic compounds and belongs to the emerging class of intermetalloid clusters. The shape of the fourth cluster, [Bi3Ni6(CO)9]3-, can be derived from the icosahedral Ni-centered [Ni@[Bi6Ni6(CO)8]4- by removal of three Bi- and one Ni-atoms of two neighboring triangular faces. The clusters were structurally characterized by single-crystal X-ray diffraction in compounds with potassium cations sequestered by 2,2,2-crypt or 18-crown-6 ether. They were also characterized in solution by electrospray mass spectrometry.     

Y2O3包覆LiCo1/3Ni1/3Mn1/3O2的电化学性能

通过在硝酸钇水溶液浸渍并焙烧的简单工艺, 在LiCo1/3Ni1/3Mn1/3O2材料表面包覆了一层Y2O3. 采用X射线衍射(XRD), 扫描电子显微镜(SEM), 透射电子显微镜(TEM), 循环伏安(CV)和恒流充放电对包覆和未包覆的LiCo1/3Ni1/3Mn1/3O2进行了测试分析. 结果表明, Y2O3包覆并没有改变LiCo1/3Ni1/3Mn1/3O2的晶体结构, 只存在于LiCo1/3Ni1/3Mn1/3O2的表面; 与未包覆的材料相比, Y2O3包覆后的材料在高电位下具有更好的容量保持率和放电容量. CV测试表明, 包覆层的存在有效抑制了材料层状结构的转变及电极与电解液的负反应.     

Synthesis,Crystal Structure and Magnetic Properties of a Two-Dimensional Heterometallic Assembly ∣[Mn(salen)]∣2∣[Ni(CN)4∣·1/2H2O

A heterometallic assembly, [Mn(salen)]₂[Ni(CN)₄ ]·1/2H₂O (where salen=N, N'-ethylene-bis(salicylideneiminato)-dianion), has been prepared from the reaction of [Mn(salen)H₂O]ClO₄ ·H₂O with K₂ [Ni(CN)₄ ]·H₂O in methanol/water. The compound crystallizes in the tetragonal space group P 4/ncc with the cell dimensions of a =14.604(2) Å, c =16.949(3) Å, and Z=4. The compound assumes a two-dimensional distorted square network structure, formed from Ni―CN―Mn(salen)―NC―Ni linkages with dimensions of Ni―C = 1.867(7)Å, Mn―N - 2.312(6) Å, Mn―N―C - 163.8(6)° Ni―C―N = 178.4(6)°. The two metal atoms Ni(II) and MN(III) have square and slightly distorted octahedral arrangements, respectively. Magnetic susceptibility measurements indicate the presence of an intramolecular antiferro-magnetic interaction and gives a Mn―Mn exchange integral of ?3.2cm^?1.     

Investigation of the charge compensation mechanism on the electrochemically Li-ion deintercalated Li1-xCo1/3Ni1/3Mn1/3O2 electrode system by combination of soft and hard X-ray absorption spectroscopy

In situ hard X-ray absorption spectroscopy (XAS) at metal K-edges and soft XAS at O K-edge and metal L-edges have been carried out during the first charging process for the layered Li1-xCo1/3Ni1/3Mn1/3O2 cathode material. The metal K-edge XANES results show that the major charge compensation at the metal site during Li-ion deintercalation is achieved by the oxidation of Ni2+ ions, while the manganese ions and the cobalt ions remain mostly unchanged in the Mn4+ and Co3+ state. These conclusions are in good agreement with the results of the metal K-edge EXAFS data. Metal L-edge XAS results at different charge states in both the FY and PEY modes show that, unlike Mn and Co ions, Ni ions at the surface are oxidized to Ni3+ during charge, whereas Ni ions in the bulk are further oxidized to Ni4+ during charge. From the observation of O K-edge XAS results, we can conclude that a large portion of the charge compensation during Li-ion deintercalation is achieved in the oxygen site. By comparison to our earlier results on the Li1-xNi0.5Mn0.5O2 system, we attribute the active participation of oxygen in the redox process in Li1-xCo1/3Ni1/3Mn1/3O2 to be related to the presence of Co in this system.     

Mn改性Ni/K/MoS2合成低碳醇催化剂反应性能研究

以不同的添加方式在Ni/K/MoS2催化剂中加入Mn助剂，考察其合成醇反应性能。结果表明，Mn/Ni/K/MoS2催化剂具有较好的合成低碳混合醇反应性能。共沉淀法以醋酸锰为前驱体加入0.6%的Mn助剂后，C2+含量，醇时空产率及选择性均明显提高;分步沉淀法使Mn的加入量增加到0.6%，醇时空产率明显增加。以浸渍法按化学计量加入Mn助剂考察其含量对催化剂合成醇性能的影响，当Mn/Mo（原子比）为1∶时，反应条件为315 ℃, 9.5 MPa, 6 000 h－1，醇时空产率和醇选择性分别达到最高值0.338?g/mL·h和69.6%。300 h的稳定性测试结果表明，共沉淀法改性的催化剂具有良好的稳定性。     

Comparison of aqua regia and HNO3-H2O2 procedures for extraction of Tl and some other elements from soils

The relationship between aqua regia (ISO 11466) and HNO(3)-H(2)O(2) (ISO/CD 20279) extraction procedures for atomic emission spectrometric (ICP/OES and ICP/MS) determinations of Tl, P, Mn, Fe, Mg, Ca, Sr, Al, K, As, Bi, Zn, Pb, Co, Cd, Ni, V, Be, Cu and Cr was investigated. Soil samples (155) representing areas with different contents of the elements were selected for the comparison. Tl was the element of the highest interest and therefore the sampling sites were chosen to achieve as wide range of Tl contents as possible. Both extraction procedures are comparable in results (differences lower than 10% for the most of the elements) for all the tested elements. Statistically non-significant differences between the two extraction procedures were found for P, Zn, V and K (the slope was very close to 1 and the intercept included zero). Statistically significant values of intercepts were found for Fe, Al, Ca, Cd, Sr and Ni. Significantly higher results for aqua regia were found for Cu (12%), Pb (17%), Mn (11%) and lower results by aqua regia were found for Mg (4%), As (13%), Co (20%), Be (11%), Cr (4%) and Bi (6%). The results for Tl, the element of the highest interest, after HNO(3)-H(2)O(2) extraction procedure, were approximately 6% higher than the results after aqua regia extraction. Content of Tl in the soil samples was from 0.08 to 2.8 mg kg(-1). A highly significant linear relationship was found (R(2)=0.97).     

Tridentate facial ligation of tris(pyridine-2-aldoximato)nickel(II) and tris(imidazole-2-aldoximato)nickel(II) To generate NiIIFeIIINiII, MnIIINiII, NiIINiII, and ZnIINiII and the electrooxidized MnIVNiII, NiIINiIII, and ZnIINiIII species: a magnetostructural, electrochemical, and EPR spectroscopic study

Eight hetero- and homometal complexes 1-6, containing the metal centers Ni(II)Fe(III)Ni(II) (1), Mn(III)Ni(II) (2), Ni(II)Ni(II) (3a-c and 4), Zn(II)Ni(II) (5), and Zn(II)Zn(II) (6), are described. The tridentate ligation property of the metal complexes tris(pyridine-2-aldoximato)nickel(II) and tris(1-methylimidazole-2-aldoximato)nickel(II) with three facially disposed pendent oxime O atoms has been utilized to generate the said complexes. Complex 1 contains metal centers in a linear arrangement, as is revealed by X-ray diffraction. Complexes were characterized by various physical methods including cyclic voltammetry (CV), variable-temperature (2-290 K) magnetic susceptibility, electron paramagnetic resonance (EPR) measurements, and X-ray diffraction methods. Binuclear complexes 2-6 are isostructural in the sense that they all contain a metal ion in a distorted octahedral environment MN(3)O(3) and a second six-coordinated Ni(II) ion in a trigonally distorted octahedral NiN(6) geometry. Complexes 1-4 display antiferromagnetic exchange coupling of the neighboring metal centers. The order of the strength of exchange coupling in the isostructural Ni(II)2 complexes, 3a-c, and 4, demonstrates the effects of the remote substituents on the spin coupling. The electrochemical measurements CV and square wave voltammograms (SQW) reveal two reversible metal-centered oxidations, which have been assigned to the Ni center ligated to the oxime N atoms, unless a Mn ion is present. Complex 2, Mn(III)Ni(II), exhibits a reduction of Mn(III) to Mn(II) and two subsequent oxidations of Mn(III) and Ni(II) to the corresponding higher states. These assignments of the redox processes have been complemented by the X-band EPR measurements. That the electrooxidized species [3a]+, [3b]+, [3c]+, and [4]+ contain the localized mixed-valent NiIINiIII system resulting from the spin coupling, a spin quartet ground state, S(t) = 3/2, has been confirmed by the X-band EPR measurements.     

Self-assembled polynuclear clusters derived from some flexible polydentate dihydrazide ligands

Polynuclear manganese(II), cobalt(II)/(III), iron(II)/(III) and nickel(II) complexes of a group of flexible polydentate dihydrazone ligands, based on pyridine-2,6-dipicolinic (A), oxalic (B) and malonic (C) subunits are described. Structural details are reported for the linear dinuclear complexes [Ni2(2poap)2(H2O)2](NO3)4 . 2CH3OH . 2.5H2O (1), [Mn2(pttp)(NO3)2(CH3OH)2(H2O)2](NO3)2 . H2O (2) and [Mn2(mapttp)2(NO3)2(H2O)2](NO3)2 . 10H2O (3), a square tetranuclear complex [Co4(pttp)4]Br6 . 9H2O (4), a tetranuclear tetrahedral complex [Ni4(pttp)6](BF4)6F2 . 14H2O (7), and a mixed spin state tetranuclear Ni(II) complex [(2pyoap)2Ni4(CH3OH)4] . 1.5CH3OH (10), with a diamond-like arrangement of metal ions. The paramagnetic metal centers are well separated in each case, leading to weak antiferromagnetic coupling or non-existent spin exchange.     

Structure and magnetic exchange in heterometallic 3d-3d transition metal triethanolamine clusters

Synthetic methods are described that have resulted in the formation of seven heterometallic complexes, all of which contain partially deprotonated forms of the ligand triethanolamine (teaH(3)). These compounds are [Mn(III)(4)Co(III)(2)Co(II)(2)O(2)(teaH(2))(2)(teaH)(0.82)(dea)(3.18)(O(2)CMe)(2)(OMe)(2)](BF(4))(2)(O(2)CMe)(2)·3.18MeOH·H(2)O (1), [Mn(II)(2)Mn(III)(2)Co(III)(2)(teaH)(4)(OMe)(2)(acac)(4)](NO(3))(2)·2MeOH (2), [Mn(III)(2)Ni(II)(4)(teaH)(4)(O(2)CMe)(6)]·2MeCN (3), [Mn(III)(2)Co(II)(2)(teaH)(2)(sal)(2)(acac)(2)(MeOH)(2)]·2MeOH (4), [Mn(II)(2)Fe(III)(2)(teaH)(2)(paa)(4)](NO(3))(2)·2MeOH·CH(2)Cl(2) (5), [Mn(II)Mn(III)(2)Co(III)(2)O(teaH)(2)(dea)(Iso)(OMe)(F)(2)(Phen)(2)](BF(4))(NO(3))·3MeOH (6) and [Mn(II)(2)Mn(III)Co(III)(2)(OH)(teaH)(3)(teaH(2))(acac)(3)](NO(3))(2)·3CH(2)Cl(2) (7). All of the compounds contain manganese, combined with 3d transition metal ions such as Fe, Co and Ni. The crystal structures are described and examples of 'rods', tetranuclear 'butterfly' and 'triangular' Mn(3) cluster motifs, flanked in some cases by diamagnetic cobalt(III) centres, are presented. Detailed DC and AC magnetic susceptibility and magnetization studies, combined with spin Hamiltonian analysis, have yielded J values and identified the spin ground states. In most cases, the energies of the low-lying excited states have also been obtained. The features of note include the 'inverse butterfly' spin arrangement in 2, 4 and 5. A S = 5/2 ground state occurs, for the first time, in the Mn(III)(2)Mn(II) triangular moiety within 6, the many other reported [Mn(3)O](6+) examples having S = ? or 3/2 ground states. Compound 7 provides the first example of a Mn(II)(2)Mn(III) triangle, here within a pentanuclear Mn(3)Co(2) cluster.     

Hydrogen-bonded networks through second-sphere coordination

The reaction of 4, 7-phenanthroline (1) with aqueous transitionmetal complexes [Mn(H2O)6][NO3]2, [Co(H2O)6][NO3]2, [Ni(H2O)6[NO3]2, [Mn(H2O)6][ClO4]2, and [Co(H2O)6][ClO4]2 does not produce coordination complexes between these metal cations and the N-donor ligand as expected. Instead, supramolecular hydrogenbonded networks are formed between the nitrogen donor atoms of 4, 7-phenanthroline and the OH groups of coordinated water molecules: M-O-H...N interactions. This motif of second-sphere coordination for 1 can be exploited as a tool for crystal engineering. As a demonstration of the generality of this new interaction as a supramolecular building block, five X-ray crystal structures are reported that utilise this hydrogen bonding scheme; [Co(H2O)4(NO3)2].(1)2 (2a), [Co(MeCN)2(H2O)4][ClO4]2.(1)2 (2b), [Ni(H2O)4(NO3)2].(1)2 (3a), [Mn(H2O)4(NO3)2].(1)2 (4a), and [Mn(H2O)6][ClO4]2.(1)(4).4H2O (4b). Each network involves complete saturation of the hydrogen-bond donor sets between the aqua complex and 1 using primarily M-O-H...N(1) and M-O-H...O(anion), interactions. Thermogravimteric analysis shows these materials to have stabililities similar to coordination polymers involving metal-ligand bonds; this demonstrates that second-sphere hydrogen bonding has potential for the construction of polymeric metal-containing materials.     

The building block approach to extended solids: 3,5-pyrazoledicarboxylate coordination compounds of increasing dimensionality

A series of M(II) complexes with the ligand 3,5-pyrazoledicarboxylic acid (H3dcp) has been synthesised mainly via hydrothermal reactions and their structures have been characterised. Simple mononuclear [Ni(Hdcp)(H2O)4] (1), Na2(mu-H2O)2(H2O)8[Ni(Hdcp)2(H2O)2] (2), [M(H2dcp)2(H2O)2] x 2H2O [M = Co (3), Zn (4) and Cu (5)] and dinuclear (Et3NH)2[Cu2(dcp)2(H2O)2] (9) building blocks have been isolated and subsequently linked into 1-D chains [Mn(Hdcp)(H2O)2]infinity (6), [[Mn(H2O)4][Mn(Hdcp)2(H2O)2] x 4H2O]infinity (7), [Ni2(Hdcp)2(mu-H2O)2(H2O)2]infinity (8), [[Ni(H2O)4][Ni2(dcp)2(H2O)4]]infinity (11), or 3-D arrays [[Na2(mu-H2O)2][Cu2(dcp)2]]infinity (10), [Cu3(dcp)2(H2O)4]infinity (12), utilising novel bridging modes of the H3dcp ligand. In the unprecedented 1-D Ni(II) chain 8, rarely reported double aqua-bridges link the Ni(II) ions to form an inter-linked double stranded chain. The magnetic properties of these compounds have been measured and reveal a variety of antiferromagnetic coupling behaviours induced by the ligand bridging modes.     

Coordination polymers with end-on azido and pyridine carboxylate N-oxide bridges displaying long-range magnetic ordering with low dimensional character

A series of 2D and one 3D transition-metal-azido coordination polymers with pyridine carboxylate N-oxide, isonicotinate N-oxide (INO), and nicotinate N-oxide (NNO) as the coligands were synthesized by a hydrothermal method and structurally and magnetically characterized. These complexes have the formulas [M(L)(N3)(H2O)]n (L = INO and M = Mn, 1.Mn; Co, 2.Co; Ni, 3.Ni and L = NNO and M = Mn, 4.Mn; Co, 5.Co; Ni, 6.Ni) and [Cu(L)(N3)(H2O)(0.5)]n (L = INO, 7.Cu; NNO, 8.Cu). All complexes consist of end-on azido and syn-syn carboxylato mixed-bridged M-N(3)/COO chains that are further linked by the pyridine N-oxide group of the INO or NNO to give rise to 2D layered structures for 1.Mn, 2.Co, 3.Ni, 4.Mn, 5.Co, 6.Ni, and 8.Cu and a 3D framework for 7.Cu. The high-temperature magnetic susceptibilities are dominated by low-dimensional behavior while long-range ordering sets in at low temperatures. The Mn complexes are antiferromagnets, and the others are metamagnets. In addition, 5.Co exhibits slow magnetic relaxation behavior at low temperatures. The metamagnetism in each case is due to strong intrachain ferromagnetic interactions and weak interchain antiferromagnetic ones.     

2D coordination polymers of macrocyclic oxamide with polycarboxylates: syntheses, crystal structures and magnetic properties

Five new 2D coordination polymers, [Co(nip)(CuL)(H(2)O)]·CH(3)OH (1), [Mn(ip)(NiL)]·0.63H(2)O (2), [Cu(ip)(CuL)] (3), [Mn(6)(CuL)(6)(btc)(4)(H(2)O)(4)]·7H(2)O (4), and [Cu(CuL)(Hbtc)(H(2)O)] (5)(ML, H(2)L = 2,3-dioxo-5,6,14,15-dibenzo-1,4,8,12-tetraazacyclo-pentadeca-7,13-diene; H(2)nip = 5-nitroisophthalic acid; H(2)ip = m-isophthalic acid; H(3)btc = 1,3,5-benzenetricarboxylic acid) have been synthesized by a solvothermal method and characterized by single-crystal X-ray diffraction. Complexes 1-5 exhibit different 2D layered structures formed by Co(2)Cu(2) (1), Mn(2)Ni(2) (2), Cu(4) (3), Mn(3)Ni(3) (4), Cu(4) (5) units, respectively, via the oxamide and diverse carboxylic acid bridges. Compounds 1, 2, 3 and 5 are uninodal 4-connected (4, 4)-grids topology, while complex 4 possesses a 2D network with (3, 4)-connected (4(2).8)(4)(4(3).6(2).8)(3) topology. The results of magnetic determination show pronounced antiferromagnetic interactions in 1-4.     

Effect of Various Synthesis methods on the Electrochemical Properties of LiNi1/3Co1/3Mn1/3O2

Layered LiNi1/3Co1/3Mn1/3O2 has the isostructure of α-NaFeO2 and shows high rate capacity with stable cycleability. Furthermore, the thermal behavior of this material is milder than that of lithium nickel oxide and lithium cobalt oxide. In addition, it is expected to be stable at elevated temperatures. Therefore LiNi1/3Co1/3Mn1/3O2 may be the most promising cathode materials of lithium-ion secondary battery.In this research, LiNi1/3Co1/3Mn1/3O2 was prepared by solid-state reaction, sol-gel method and mixed hydroxide method. The influences of synthesis method on the physical and electrochemical properties of LiNi1/3Co1/3Mn1/3O2 were characterized by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), charge/discharge cycling cyclic voltammetry and differential scanning calorimetry (DSC). XPS studies show that the predominant oxidation states of Ni, Co and Mn in the LiNi1/3Co1/3Mn1/3O2 compound are 2+, 3+ and 4+. From the voltage profile and cyclic voltammetry, the redox processes occurring at ～3.8V and ～4.5V are assigned to the Ni2+/Ni3+ and Co3+/Co4+ couples, respectively. Different preparation methods result in the difference in morphology (shape, particle size and specific surface area) and electrochemical behaviors. A sample prepared by solid-state reaction has the worst electrochemical performance among these three methods. Sample synthesized by mixed hydroxide method displays the better rate capacity than that prepared by sol-gel method, while the capacity retention of sample prepared by sol-gel method is superior to that synthesized by mixed hydroxide method.     

TiO2包覆对LiCo1/3Ni1/3Mn1/3O2材料的表面改性

为了提高材料LiCo1/3Ni1/3Mn1/3O2的循环性能, 采用浸渍-水解法对其进行TiO2包覆. 用X射线衍射(XRD)、电化学交流阻抗谱(EIS)、电感耦合等离子体发射光谱(ICP-OES)和恒流充放电测试研究包覆材料的结构和电化学性能. TiO2仅在材料表面形成包覆层, 并未改变材料的结构. TiO2包覆能提高材料LiCo1/3Ni1/3Mn1/3O2的倍率性能和循环性能, TiO2包覆后的材料在5.0C(1.0C=160 mA·g-1)下的放电容量达到0.2C下的66.0%, 而包覆前的材料在5.0C下的放电容量仅为其0.2C下的31.5%. 包覆后的材料在2.0C下循环12周后的容量没有衰减, 而未包覆的材料容量保持率仅为94.4%. EIS测试表明包覆材料性能的提高是由于循环过程中材料的界面稳定性得到了提高. 循环后材料的XRD和ICP-OES测试表明, 包覆层能提高材料LiCo1/3Ni1/3Mn1/3O2的结构稳定性.