The tunnel manganese oxide Na4.32Mn9O18: a new Na+ site discovered by single‐crystal X‐ray diffraction

The title compound, tetrasodium nonamanganese octadecaoxide, Na_4.32Mn₉O₁₈, was synthesized by reacting Mn₂O₃ with NaCl. One Mn atom occupies a site of 2/m symmetry, while all other atoms sit on mirror planes. The compound is isostructural with Na₄Ti₄Mn₅O₁₈ and suggestive of Mn³⁺/Mn⁴⁺ charge ordering. It has a double‐tunnel structure built up from double and triple chains of MnO₆ octahedra and single chains of MnO₅ square pyramids by corner sharing. Disordered Na⁺ cations occupy four crystallographic sites within the tunnels, including an unexpected new Na⁺ site discovered inside the large S‐shaped tunnel. A local‐ordering model is used to show the possible Na⁺ distribution, and the unit‐cell evolution during charging/discharging is explained on the basis of this local‐ordering model.     

The novel arsenate Na4Co7−xAl2/3x(AsO4)6 (x = 1.37): crystal structure,charge‐distribution and bond‐valence‐sum investigations

The title compound, tetrasodium cobalt aluminium hexaarsenate, Na₄Co_7−xAl_2/3x(AsO₄)₆ (x = 1.37), is isostructural with K₄Ni₇(AsO₄)₆; however, in its crystal structure, some of the Co²⁺ ions are substituted by Al³⁺ in a fully occupied octahedral site (site symmetry 2/m) and a partially occupied tetrahedral site (site symmetry 2). A third octahedral site is fully occupied by Co²⁺ ions only. One of the two independent tetrahedral As atoms and two of its attached O atoms reside on a mirror plane, as do two of the three independent Na⁺ cations, all of which are present at half‐occupancy. The proposed structural model based on a careful investigation of the crystal data is supported by charge‐distribution (CHARDI) analysis and bond‐valence‐sum (BVS) calculations. The correlation between the X‐ray refinement and the validation results is discussed.     

Crystal Chemistry of the M11+,2+–M22+,3+–(H)‐Arsenites: the First Cadmium(II) Arsenite,Na4Cd7(AsO3)6

The crystal structures among M1–M2–(H)‐arsenites (M1 = Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Ca²⁺, Sr²⁺, Ba²⁺, Cd²⁺, Pb²⁺; M2 = Mg²⁺, Mn^2+,3+, Fe^2+,3+, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺) are less investigated. Up to now, only the structure of Pb₃Mn(AsO₃)₂(AsO₂OH) was described. The crystal structure of hydrothermally synthesized Na₄Cd₇(AsO₃)₆ was solved from the single‐crystal X‐ray diffraction data. Its trigonal crystal structure [space group R$\bar{3}$ , a = 9.5229(13), c = 19.258(4) Å, γ = 120°, V = 1512.5(5) ų, Z = 3] represents a new structure type. The As atoms are arranged in monomeric (AsO₃)^3– units. The surroundings of the two crystallographically unique sodium atoms show trigonal antiprismatic coordination, and two mixed Cd/Na sites are remarkably unequal showing tetrahedral and octahedral coordinations. Despite the 3D connection of the AsO₃ pyramids, (Cd,Na)O_x polyhedra and NaO₆ antiprisms, a layer‐like arrangement of the Na atoms positioned in the hexagonal channels formed by CdO₄ deformed tetrahedra and AsO₃ pyramids in z = 0, 1/3, 2/3 is to be mentioned. These pseudo layers are interconnected to the 3D network by (Cd,Na)O₆ octahedra. Raman spectra confirmed the presence of isolated AsO₃ pyramids.     

P2‐Na0.67AlxMn1−xO2: Cost‐Effective,Stable and High‐Rate Sodium Electrodes by Suppressing Phase Transitions and Enhancing Sodium Cation Mobility

Sodium layered P2‐stacking Na_0.67MnO₂ materials have shown great promise for sodium‐ion batteries. However, the undesired Jahn–Teller effect of the Mn⁴⁺/Mn³⁺ redox couple and multiple biphasic structural transitions during charge/discharge of the materials lead to anisotropic structure expansion and rapid capacity decay. Herein, by introducing abundant Al into the transition‐metal layers to decrease the number of Mn³⁺, we obtain the low cost pure P2‐type Na_0.67Al_xMn_1?xO₂ (x=0.05, 0.1 and 0.2) materials with high structural stability and promising performance. The Al‐doping effect on the long/short range structural evolutions and electrochemical performances is further investigated by combining in situ synchrotron XRD and solid‐state NMR techniques. Our results reveal that Al‐doping alleviates the phase transformations thus giving rise to better cycling life, and leads to a larger spacing of Na⁺ layer thus producing a remarkable rate capability of 96 mAh g^‐1 at 1200 mA g^‐1.     

P2‐Na0.67AlxMn1−xO2: Cost‐Effective,Stable and High‐Rate Sodium Electrodes by Suppressing Phase Transitions and Enhancing Sodium Cation Mobility

Sodium layered P2‐stacking Na_0.67MnO₂ materials have shown great promise for sodium‐ion batteries. However, the undesired Jahn–Teller effect of the Mn⁴⁺/Mn³⁺ redox couple and multiple biphasic structural transitions during charge/discharge of the materials lead to anisotropic structure expansion and rapid capacity decay. Herein, by introducing abundant Al into the transition‐metal layers to decrease the number of Mn³⁺, we obtain the low cost pure P2‐type Na_0.67Al_xMn_1?xO₂ (x=0.05, 0.1 and 0.2) materials with high structural stability and promising performance. The Al‐doping effect on the long/short range structural evolutions and electrochemical performances is further investigated by combining in situ synchrotron XRD and solid‐state NMR techniques. Our results reveal that Al‐doping alleviates the phase transformations thus giving rise to better cycling life, and leads to a larger spacing of Na⁺ layer thus producing a remarkable rate capability of 96 mAh g^‐1 at 1200 mA g^‐1.     

An arsenate with the α‐CrPO4 structure type,NaCa1–xNi3–2xAl2x(AsO4)3 (x = 0.23): crystal structure,charge‐distribution and bond‐valence‐sum analyses

Since the discovery of electrochemically active LiFePO₄, materials with tunnel and layered structures built up of transition metals and polyanions have become the subject of much research. A new quaternary arsenate, sodium calcium trinickel aluminium triarsenate, NaCa_1–x Ni_3–2x Al_2x (AsO₄)₃ (x = 0.23), was synthesized using the flux method in air at 1023 K and its crystal structure was determined from single‐crystal X‐ray diffraction (XRD) data. This material was also characterized by qualitative energy‐dispersive X‐ray spectroscopy (EDS) analysis and IR spectroscopy. The crystal structure belongs to the α‐CrPO₄ type with the space group Imma . The structure is described as a three‐dimensional framework built up of corner‐edge‐sharing NiO₆, (Ni,Al)O₆ and AsO₄ polyhedra, with channels running along the [100] and [010] directions, in which the sodium and calcium cations are located. The proposed structural model has been validated by bond‐valence‐sum (BVS) and charge‐distribution (CHARDI) tools. The sodium ionic conduction pathways in the anionic framework were investigated by means of the bond‐valence site energy (BVSE) model, which predicted that the studied material will probably be a very poor Na⁺ ion conductor (bond‐valence activation energy ∼7 eV).     

Na3F[WO4]: A Sodium Fluoride Ortho‐Oxotungstate(VI) with Strands of Face‐Shared Fluoride‐Centred Sodium Octahedra According to $^{1}_{\infty}\rm \{[FNa_{6/2}]^{2+}\}$

During the reaction of Na₂[WO₄] with YF₃ purposed to yield fluoride‐derivatized yttrium oxotungstates(VI), colourless platelet‐shaped single crystals of Na₃F[WO₄] emerged as main product. The title compound crystallizes orthorhombically in the space group Pnma (a = 559.59(5), b = 751.02(7), c = 1285.98(9) pm) with four formula units per unit cell. Besides isolated ortho‐oxotungstate units [WO₄]^2? (d(W–O) = 176–178 pm) the crystal structure contains two crystallographically independent Na⁺ cations which are both octahedrally coordinated by four oxygen atoms and two fluoride anions. The F^? anions are surrounded by six sodium cations (d(F–Na) = 224–242 pm) also in an octahedral fashion. These octahedra built up chains along [100] by sharing trans‐oriented faces according to , which are stacked according to a hexagonal closest rod‐packing. The cationic strands are surrounded, interconnected and charge‐balanced by isolated [WO₄]^2? tetrahedra with almost ideal shape and every O^2? ligand is terminally coordinated by three Na⁺ cations.     

Factors Influence Complexing Selectivity of Lariat Crown Ethers Toward Alkali Metal Ions in Electrospray Ionization Mass Spectrometry

The selectivity of eight lariat crown ethers in the sym‐dibenzo‐16‐crown‐5 series toward alkali metal ions was studied with electrospray ionization mass spectrometry under different conditions. With the exception of 2g , which is equally selective toward Na⁺ and Li⁺, all other lariat crown ethers show the best selectivity toward Li⁺ in methanol. Factors that influence the selectivity include the water content, counterions, nature of the side arms, and the externally added cations. Iodide gives the best Na⁺ selectivity with R_I > R_Br > R_Cl. Increased water content profoundly increases the Na⁺ selectivity when the side arm is hydrophilic and the steric hindrance is small. Externally added cations (Cs⁺ and/or Rb⁺) enhance the Na⁺ selectivity by exchanging the smaller Li⁺ from the cavity.     

Bis[μ3‐1,8‐bis(triisopropylsilylamido)naphthalene]bis(tetrahydrofuran)di‐μ3‐oxido‐dimanganese(III)disodium

The solid‐state structure of the title compound, [Na₂Mn₂(C₃₂H₅₆N₂OSi₂)₂O₂] or [1,8‐C₁₀H₆(NSiⁱPr₃)₂Mn(μ₃‐O)Na(THF)]₂, which lies across a crystallographic twofold axis, exhibits a central [Mn₂O₂Na₂]⁴⁺ core, with two oxide groups, each triply bridging between the two Mn^III ions and an Na⁺ ion. Additional coordination is provided to each Mn^III centre by a 1,8‐C₁₀H₆(NSiⁱPr₃)₂ [1,8‐bis(triisopropylsilylamido)naphthalene] ligand and to the Na⁺ centres by a tetrahydrofuran molecule. The presence of an additional Na...H—C agostic interaction potentially contributes to the distortion around the bridging oxide group.     

From Racemic Compound to Spontaneous Resolution: A Linker‐Imposed Evolution of Chiral [MnMo9O32]6−‐Based Polyoxometalate Compounds

Five compounds based on [MnMo₉O₃₂]^6?: (Himi)₆[MnMo₉O₃₂] ( 1 ) (imi=imidazole), Na₂(Himi)₄[MnMo₉O₃₂] ? 2 H₂O ( 2 ), Na₃(Himi)₃[MnMo₉O₃₂] ( 3 ), D ‐NH₄Mn_2.5[MnMo₉O₃₂] ? 11 H₂O ( 4 a ), and L ‐NH₄Mn_2.5[MnMo₉O₃₂] ? 11 H₂O ( 4 b ) were prepared and characterized. X‐ray crystallographic analysis revealed that compounds 1 and 2 with imidazole molecules as linkers are racemic compounds; compound 3 is a racemic solid solution of Na⁺ cations and the polyoxoanion [MnMo₉O₃₂]^6?; and compounds 4 a and 4 b are enantiomers. In compound 4 , the homochiral polyoxoanions [MnMo₉O₃₂]^6? are connected by Mn²⁺ cations to form a unique (4⁵ ? 6)(4⁷ ? 6⁸) topology net framework. By adjusting the linkers from imidazole molecules to Na⁺ and finally Mn²⁺ cations, the chiral polyoxoanions [MnMo₉O₃₂]^6? were changed from a racemic compound to a conglomerate. This means that spontaneous resolution can be efficiently realized by connecting homochiral polyoxoanions into one‐dimensional (1D), 2D, and 3D structures, with an emphasis on using appropriate linkers with substantial interaction strength, directionality, and enantioselectivity.     

Magnetic “Molecular Oligomers” Based on Decametallic Supertetrahedra: A Giant Mn49 Cuboctahedron and its Mn25Na4 Fragment

Two nanosized Mn₄₉ and Mn₂₅Na₄ clusters based on analogues of the high‐spin (S=22) [Mn^III₆Mn^II₄(μ₄‐O)₄]¹⁸⁺ supertetrahedral core are reported. Mn₄₉ and Mn₂₅Na₄ complexes consist of eight and four decametallic supertetrahedral subunits, respectively, display high virtual symmetry (O_h), and are unique examples of clusters based on a large number of tightly linked high nuclearity magnetic units. The complexes also have large spin ground‐state values (Mn₄₉: S=61/2; Mn₂₅Na₄: S=51/2) with the Mn₄₉ cluster displaying single‐molecule magnet (SMM) behavior and being the second largest reported homometallic SMM.     

The synthesis of novel crown ethers,part X, 4‐propyl‐and 3‐ethyl‐4‐methylchromenone‐crown ethers

Starting from ethyl propionylacetate, and ethyl 2‐ethylacetoacetate we prepared 4‐propyl‐7,8‐, 4‐propyl‐6,7‐, 3‐ethyl‐4‐methyl‐7,8‐ and 3‐ethyl‐4‐methyl‐6,7‐dihydroxy‐2H‐chromenones which were allowed to react with the bis‐dihalides or ditosylates of glycols in DMF/Na₂CO₃ to afford the 6,7‐ and 7,8‐chromenone derivatives of 12‐crown‐4, 15‐crown‐4 and 18‐crown‐6. The products were identified using ir, ¹³C and ¹H nmr, ms and high resolution mass spectroscopy. The cation selectivities of chromenone crown ethers with Li⁺, Na⁺ and K⁺ cations were estimated from the steady state emission fluorescence spectra of free and cation complexed chromenone macrocyclic ethers in acetonitrile.     

New girdle‐like Mo18 polyanions linked into chains

From the reduction of heptamolybdate, a polyoxomolybdate was obtained with the formula [Na(H₂O)₁₆(NH₂CH₂­COO)]⁴⁺·{Na⁺[H₉MoMoO₅₆(NH₂CH₂COO)]^5?}^4?­·20H₂O, i.e. hepta­sodium nona­hydrogen tetra­car­bam­ate hexa­deca­aqua­hexa­penta­conta­oxa­octa­deca­molyb­date(V,VI) icosa­hydrate. The 18 Mo atoms are connected by bridging O atoms to form a centrosymmetric girdle‐like structure, in which Mo^V–Mo^V units are found. An Na⁺ cation occupies the central hole of the girdle, while four Na⁺ cations are bonded to the O atoms on the girdle edge. The girdles are linked into a one‐dimensional chain by the other Na⁺ cations.     

Na6(H2O)20(V10O28)·4H2O,a novel polyvanadate(V) with a three‐dimensional framework

The novel title polyvanadate(V), poly[[octa‐μ‐aqua‐dodecaaqua‐μ₄‐octacosaoxidodecavanadato‐hexasodium] tetrahydrate], [Na₆(H₂O)₂₀(V₁₀O₂₈)·4H₂O]_n, contains [V₁₀O₂₈]⁶⁻ anions which lie about inversion centres and have approximate 2/m symmetry and which are linked to [Na₃(H₂O)₁₀]³⁺ cations through two terminal and two μ₂‐bridging O atoms. The structure contains three inequivalent Na⁺ cations, two of which form [Na₂(H₂O)₈]_n chains, which are linked via NaO₆ octahedra involving the third Na⁺ ion, thus forming a three‐dimensional framework.     

Synthesis,Crystal Structure,and Characterization of Na7Cu4(AsO4)5

Abstract

Sodium copper (II) arsenate Na₇Cu₄(AsO₄)₅ has been grown by conventional high-temperature, solid-state methods in molten-salt media. It was characterized by single crystal X-ray diffraction (XRD), thermal analysis (DTA–TGA), scanning electron microscopy (SEM), semiquantitative energy dispersive spectroscopy analysis (EDS), and vibrational spectroscopy. Na₇Cu₄(AsO₄)₅ exhibits a three-dimensional framework built up of CuO₅, CuO₄, and AsO₄ polyhedra, with intersecting channels in which the Na⁺ cations are located. The three-dimensional cohesion of the framework results from Cu–O–As bridges. CuO₅ and CuO₄ polyhedra are elongated due to the Jahn–Teller effect, whereas AsO₄ tetrahedra are almost regular. This new structural model is validated by the charge distribution (CD) analysis. The infrared and Raman spectra confirmed the presence of AsO₄ tetrahedra.

[Supplementary materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfer, and Silicon and the Related Elements for the following free supplemental files: Additional tables and figures.]     

Sorption of transition metal cations on natural heulandite

The cation exchange equilibrium in the systems of natural heulandite-binary aqueous solutions of NaCl, NiCl₂, CuCl₂, ZnCl₂, and MnCl₂ was studied. The corrected coefficients of the selectivity (k ^a _M/Na) and thermodynamic constants (K _M/Na) of the cation exchange of Na⁺ cations for transition metal cations were determined. The selectivity of the cation exchange on natural heulandite increases in the following order: Ni²⁺ < Cu²⁺ < Zn²⁺ < Na²⁺ < Mn²⁺.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1101–1103, May, 1996.     

High Magnetic Moments in Manganese‐Doped Silicon Clusters

We report on the structural, electronic, and magnetic properties of manganese‐doped silicon clusters cations, Si_nMn⁺ with n=6–10, 12–14, and 16, using mass spectrometry and infrared spectroscopy in combination with density functional theory computations. This combined experimental and theoretical study allows several structures to be identified. All the exohedral Si_nMn⁺ (n=6–10) clusters are found to be substitutive derivatives of the bare Si_n+1⁺ cations, while the endohedral Si_nMn⁺ (n=12–14 and 16) clusters adopt fullerene‐like structures. The hybrid B3P86 functional is shown to be appropriate in predicting the ground electronic states of the clusters and in reproducing their infrared spectra. The clusters turn out to have high magnetic moments localized on Mn. In particular the Mn atoms in the exohedral Si_nMn⁺ (n=6–10) clusters have local magnetic moments of 4 μ_B or 6 μ_B and can be considered as magnetic copies of the silicon atoms. Opposed to other 3d transition‐metal dopants, the local magnetic moment of the Mn atom is not completely quenched when encapsulated in a silicon cage.     

Preparation of a hybrid monolithic stationary phase with allylsulfonate for the rapid and simultaneous separation of cations in capillary ion chromatography

A hybrid monolithic column with sulfonate functionality was successfully prepared for the simultaneous separation of common inorganic cations in ion‐exchange chromatographic mode through a simple and easy single‐step preparation method. The strong cation‐exchange moieties were provided directly from allylsulfonate, which worked as an organic monomer in the single‐step reaction. Inorganic cations (Li⁺, Na⁺, K⁺, NH₄⁺, Cs⁺, Rb⁺, Mg²⁺, Ca²⁺, and Sr²⁺) were separated satisfactorily by using CuSO₄ as the eluent with indirect UV detection. The allysulfonate hybrid monolith showed a better performance in terms of speed and pressure drop than the capillary packed column. The number of theoretical plates achieved was 19 017 plates/m (in the case of NH₄⁺ as the analyte). The relative standard deviations (n = 6) of both retention time and peak height were less than 1.96% for all the analyte cations. The allysulfonate hybrid monolithic column was successfully applied for the rapid and simultaneous separation of inorganic cations in groundwater and the effluent of onsite domestic wastewater treatment system.     

The Remarkable Effect of the Manganese Ion with Dioxygen on the Stability of π‐Conjugated Radical Cations

In this paper, nanosecond laser flash photolysis has been used to investigate the influence of metal ions on the kinetics of radical cations of a range of carotenoids (astaxanthin (ASTA), canthaxanthin (CAN), and β‐carotene (β‐CAR)) and various electron donors (1,4‐diphenyl‐1,3‐butadiene (14DPB), 1,6‐diphenyl‐1,3,5‐hexatriene (16DPH), 4‐methoxy‐trans‐stilbene (4 MeOSt), and trans‐stilbene (trans‐St)) in benzonitrile. Radical cations have been generated by means of photosensitized electron‐transfer (ET) using 1,4‐dicyanonaphthalene (14DCN) and biphenyl (BP). The kinetic decay of CAR ^{. +} shows a strong dependence on the identity of the examined metal ion. For example, whereas NaClO₄ has a weak effect on the kinetics of CAR ^{. +}, Ni(ClO₄)₂ causes a strong retardation of the decay of CAR ^{. +}. It is also interesting to note that Mn²⁺, which is a biologically relevant metal ion, shows the strongest effect of all the investigated metal ions (e.g., in the presence of Mn²⁺ ions, the half‐life (t_1/2) of CAN ^{. +} (t_1/2>90 ms) is more than three orders of magnitude higher than in the absence of the metal ions (t_1/2≈16 μs)). Furthermore, the influence of metal‐ion and oxygen concentrations on the kinetics of CAR ^{. +} reveals their pronounced effect on the kinetic decay of CAR ^{. +}. However, these remarkable effects are greatly diminished if either oxygen or metal ions are removed from the investigated solutions. Therefore, it can be concluded that oxygen and metal ions interact cooperatively to induce the observed substantial effects on the stabilities of CAR ^{. +}. These results are the first direct observation of the major role of oxygen in the stabilization of radical cations, and they support the earlier mechanism proposed by Astruc et al. for the role of oxygen in the inhibition of cage reactions. On the basis of these results, the factors that affect the stability of radical cations are discussed and the mechanism that shows the role of oxygen and metal ions in the enhancement of radical‐cation stability is described.     

β‐LiMoO2(AsO4)

A new non‐centrosymmetrical form of lithium molybdyl arsenate has been synthesized and grown as a single crystal. The structure of β‐LiMoO₂(AsO₄) is built up of corner‐sharing AsO₄ tetrahedra and MoO₆ octahedra which form a three‐dimensional framework containing tunnels running along the a axis, wherein the Li⁺ cations are located. This novel structure is compared with the compound LiMoO₂(AsO₄) of the same formula, and with those of AMO₂(XO₄) (A is Na, K, Rb or Pb, M is Mo or V, and X is P or As) and B(MoO₂)₂(XO₄)₂ (B is Ba, Pb or Sr).