Bis-boron-capped tris(dioxime) cage complexes with terminal carbonyl groups

Three clathrochelate complexes, [(p-OHCC₆H₄B)₂(chdd)₃Fe^II]·0.5CH₂Cl₂ (1·0.5CH₂Cl₂, H₂chdd = 1,2-cyclohexanedione-1,2-dioxime), [(p-OHCC₆H₄B)₂(hmbd)₃Mn^II₂]}·Et₃NH·0.5CH₃OH·0.5H₂O (2·0.5CH₃OH·0.5H₂O, H₃hmbd = 2-hydroxy-5-methyl-1,3-benzenedicarboxaldehyde-1,3-dioxime), and [(p-OHCC₆H₄B)₂(hmbd)₃Co^II₂]·Et₃NH·H₂O (3·H₂O), were synthesized through template macrobicyclization using metal-oximates as building blocks. These complexes contained reactive apical formyl substituents. Fe^II in mononuclear complex 1 was wrapped in the cavity formed by condensation of H₂chdd with 4-formylphenylboron acid. The organic frameworks of anion unit of binuclear Mn^II complex 2 and that of binuclear Co^II complex 3 were combined by H₃hmbd with 4-formylphenylboronic acid. Spectroscopic, electrochemical characterizations of complexes 1–3 were exploited. DFT calculation of 1 and 2 was also done for better understanding of the electronic property and charge carrier mobility.     

Spinel fibers from carboxylate precursor

A spinel precursor was synthesized from a 1:2 stoichiometric mixture of Al(O₂CH)₃·3H₂O and Mg(O₂CCH₃)₂·4H₂O dissolved in H₂O with stabilizing additives. The precursor, as well as individual compounds were characterized using TGA, DTA, DRIFTS and XRD techniques to establish decomposition profiles. During pyrolysis, Mg(O₂CCH₃)₂·4H₂O decomposes first to an amorphous oxide contaminated with minor amounts of carbonate. At 300°C, rock salt (MgO) crystallizes. The spinel precursor behaves like a separate compound and decomposes directly to crystalline spinel at ≈600°C without any evidence of phase separation. The spinel precursor is easily extruded or hand drawn to form well-defined green fibers. Extruded green fibers (20 μm dia.) were pyrolyzed at 300°C/2 h/air to remove carboxylate ligands, and then heated at 15°C/min to 1500°C/2 h/air to sinter. The mechanical strength of these fibers was evaluated using a bending test method. The final fibers are ≈10 μm in dia., with 1·2±0·4 μm grain size and offer an average bend strength of 1·0±0·4 GPa. ©     

pH-controlled the formation of 4-sulfocalix[4]arene-based 1D and 2D coordination polymers

Three manganese/4-sulfocalix[4]arene complexes, namely, {H[(C₂₈H₂₀O₁₆S₄)Mn(H₂O)₄Mn_0.5(H₂O)₂]}_n ·6nH₂O (1), {NH₄[(C₂₈H₂₀O₁₆S₄)Mn(H₂O)₄Mn_0.5(H₂O)₂]}_n · 5nH₂O (2), [(C₂₈H₂₀O₁₆S₄)Mn₂(H₂O)₈]_n · 6nH₂O (3), have been synthesized under different pH conditions. Complex 1, which exhibits a one-dimensional (1D) structure, is formed at [H⁺] = 2.0 mol L⁻¹. Reaction at pH 4 leads to another one-dimensional (1D) coordination polymer of 2. At pH 5, a two-dimensional (2D) coordination polymer of complex 3 is formed, showing clearly structural effects on pH response.     

The characteristics of Li(Ni1/3Co1/3Mn1/3)O2 particles prepared from precursor particles with spherical shape obtained by spray pyrolysis

Spherical and fine-sized Li(Ni_1/3Co_1/3Mn_1/3)O₂ particles were prepared using spray pyrolysis. Precursor particles with mixed Mn₂O₃, Co₃O₄ and NiO compositions were prepared using spray pyrolysis from aqueous and polymeric precursor solutions. The precursor particles prepared from the aqueous solution had hollow and porous morphologies. The precursor particles prepared from the polymeric precursor solution with citric acid and ethylene glycol were spherical in shape and had filled morphologies. The spherical precursor particles with filled morphologies formed spherical, fine-sized Li(Ni_1/3Co_1/3Mn_1/3)O₂ particles with filled morphologies after post-treatment with LiOH. The mean crystallite sizes of the Li(Ni_1/3Co_1/3Mn_1/3)O₂ particles prepared from spray solutions with and without lithium at the post-treatment temperature of 800 °C were 56 and 31 nm, respectively. The initial discharge capacities of the Li(Ni_1/3Co_1/3Mn_1/3)O₂ particles prepared using spray pyrolysis from spray solutions with and without lithium were 178 and 181 mAh g⁻¹, respectively, after a post-treatment temperature of 800 °C.     

Solvent-free synthesis of open-framework manganese phosphate-oxalates with 4-connected topologies

Two manganese phosphate-oxalates, namely, H₂aep·Mn₂(H₂PO₄)₂(C₂O₄)₂·H₂O (1) and H₂epip·Mn₂(H₂PO₄)₂(C₂O₄)₂ (2), were prepared under solvent-free conditions, where aep = 1-(2-aminoethyl)piperazine and epip = 1-ethylpiperzaine. The two hybrid solids have three-dimensional open-framework structures with 12-, and 16-ring channels, respectively. Topological analysis reveals that they have 4-connected lon and mog nets. The magnetic properties of the two compounds were also investigated.     

Ni-Mg-Mn-Fe-O catalyst derived from layered double hydroxide for hydrogen production by auto-thermal reforming of ethanol

Ni-Mg-Mn-Fe-O catalysts were prepared via co-precipitation through layered double hydroxide (LDH) precursors and tested for hydrogen production from ethanol by auto-thermal reforming (ATR). With Mn and Fe in the precursor of the Ni_0.35 Mg_2.65Mn_0.5Fe_0.5O_4.5 ± δ catalyst, an LDH structure formed via co-precipitation, and after calcination, a cubic MgO skeleton formed with spinel phases of NiMn₂O₄ and NiFe₂O₄. The H₂ yield reached 4.0 mol-H₂/mol-EtOH and remained stable in a 30-h ATR test, which can be attributed to the improvement of reduction behavior and stability of Ni⁰ species.     

A cyanide-bridged two-dimensional grid-like FeIII–CoII complex based on the pentacyanideferrite(III) building block

A cyanide-bridged Fe^III–Co^II heterometallic complex {[Fe(1-CH₃im)(CN)₅][Co(H₂O)₂]}n·3H₂O (1-CH₃im = 1-methylimadazole) (2) has been synthesized by the reaction of Co^II(ClO₄)₂·6H₂O with the pentacyanideferrite(III) building block (Ph₄P)₂[Fe^III(1-CH₃im)(CN)₅]·4.5H₂O (1). X-Ray single crystal diffraction analysis shows that complex 2 has a two-dimensional (2D) grid-like structure. Magnetic investigations show that complex 2 displays long-range antiferromagnetic ordering with T_N = 9.45 K. The typical metamagnetic behaviors were observed with the critical field of ca. 4000 Oe at 1.82 K.     

Synthesis,structure and magnetic properties of spinel ferrite (Ni,Cu, Co)Fe2O4 from low nickel matte

Spinel ferrite (Ni, Cu, Co)Fe₂O₄ was synthesized from the low nickel matte by using a co-precipitation-calcination method for the first time. The influences of the added amount of NiCl₂·6H₂O, calcination temperature and time on the structure and magnetic properties of the as-prepared ferrites were studied in detail by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Raman spectroscopy, and Vibrating sample magnetometer (VSM). It is indicated that pure (Ni, Cu, Co)Fe₂O₄ with cubic phase could be obtained under the experimental conditions (NiCl₂·6H₂O added amount of 3.0: 100 g mL⁻¹, calcination temperature from 800 to 1000 °C and calcination time from 1 to 3 h). With increasing calcination temperature and time, saturation magnetization (M_S) of the synthesized (Ni, Cu, Co)Fe₂O₄ increased and the coercivity (H_C) decreased. Under the optimum conditions (i.e. NiCl₂·6H₂O added amount of 3.0: 100 g mL⁻¹, 1000 °C, 3 h), the M_S and H_C values of the product were approximately 46.1 emu g⁻¹ and 51.0 Oe, respectively, which were competitive to those of other nickel ferrites synthesized from pure chemical reagents. This method explores a novel pathway for efficient and comprehensive utilization of the low nickel matte.     

Self-assembly of a Co4III face-shared partial double cubane supported by alkoxo terminal and bridging ligands

The double μ₃-OMe supported tetrameric Co₄ complex [Co₄(μ₃-OMe)₂(μ-bemp)₂(N₃)₂(OH₂)₂](ClO₄)₂ · 4H₂O {1 · (ClO₄)₂ · 4H₂O} was isolated from the reaction of Co(ClO₄)₂ · 6H₂O with H₃bemp (where H₃bemp = 2,6-bis-[(2-hydroxy-ethylimino)-methyl]-4-methyl-phenol) and NaN₃ in presence of NEt₃ in aqueous methanol. The X-ray structure analysis reveals a cationic tetrameric arrangement consisting of a defective dicubane-like core with two missing vertexes. The four Co(III) ions are connected through in situ generated μ₃-OMe and central phenolate plus terminal ethanolate bridges of the ligand. Terminal aqua and azido coordinations finally fulfil the octahedral geometries around the Co^III ions within this Co₄ aggregate.     

Preparation of new heteronuclear (NH4)RE[FeII(CN)6]·nH2O complexes (RE = La,Ce, Pr,Nd, Sm,Gd, Dy,Y, Er,Lu) and their low-temperature decomposition for perovskite-type oxide

New heteronuclear (NH₄)RE^III[Fe^II(CN)₆]·nH₂O complexes (RE = La, Ce, Pr, Nd, Sm, Gd, Dy, Y, Er, Lu) were synthesized and their thermal decomposition products were investigated. The crystal structure of (NH₄)RE[Fe^II(CN)₆]·nH₂O would be a hexagonal unit cell (space group: P6₃/m), which was the same as that of La[Fe^III(CN)₆]·5H₂O. The hydration number n = 4 was estimated by TG results for all the RE complexes. The lattice constants depended on the ionic radius of the RE³⁺ ion for the heteronuclear complexes. The single phase of the perovskite type materials was directly obtained by decomposition of the heteronuclear complexes for RE = La, Pr, Nd, Sm, and Gd. A mixture of CeO₂ and Fe₂O₃ was formed for RE = Ce because of its oxidation to Ce⁴⁺. In the case of RE = Dy, Y, Er, and Lu complexes, the perovskite type materials formed at higher temperature via. mixed oxides such as RE₂O₃ and RE₄Fe₅O₁₃ due to the small RE³⁺ ionic radius.     

Comparison of lithium nickel cobalt oxides synthesized from NiO,Co3O4, and LiOH·H2O or Li2CO3 by solid-state reaction method

LiNi_1?yCo_yO₂ (y = 0.1, 0.3 and 0.5) cathode materials were synthesized by the solid-state reaction method at different temperatures from LiOH·H₂O, NiO and Co₃O₄ and from Li₂CO₃, NiO and Co₃O₄ as the starting materials. The physical and electrochemical properties of the synthesized samples were then compared. Among LiNi_1?yCo_yO₂ (y = 0.1, 0.3 and 0.5) synthesized for 40 h from LiOH·H₂O, NiO and Co₃O₄, and from Li₂CO₃, NiO and Co₃O₄, LiNi_0.5Co_0.5O₂ synthesized from Li₂CO₃, NiO and Co₃O₄ at 800 °C has relatively large first discharge capacity and relatively good cycling performance. This sample is considered the best one with relatively good electrochemical properties.     

A helical salicyladoxime-based manganese triangle chain with single-molecule magnet behavior

The reaction of 2-hydroxyphenylpropanone oxime (Et-H₂salox) with Mn(NO₃)₂·4H₂O, NEt₃ and 1,3-bis(4-pyridyl)propane-N,N′-dioxide (bppo) in EtOH/H₂O mixture afforded a one-dimensional coordination polymer with the formula [Mn₃O(Et-salox)₃(bppo)(MeOH)(H₂O)₃](NO₃)_0.5(Et-Hsalox)_0.5·MeOH·H₂O (1·MeOH·H₂O). 1·MeOH·H₂O had a manganese triangle structure, [Mn^III₃O]^7 +, which was used as a building unit for a subsequent assembly of an oximate and central oxide. The flexible bppo ligand linked the units, resulting in the formation of a 1D helical structure. Variable temperature direct current magnetic susceptibility measurements of complex 1·MeOH·H₂O were carried out. Exchange interactions of the metal centers of complex 1·MeOH·H₂O were examined, and the results indicate that both ferro- and antiferromagnetic interactions simultaneously coexist in 1·MeOH·H₂O, resulting in an S = 2 ground state. Moreover, complex 1·MeOH·H₂O shows the frequency dependence of the out-of-phase component in alternating current magnetic susceptibility measurements, indicating single-molecule magnet behavior with U_eff = 28 K and τ₀ = 1.8 × 10^− 9 s.     

A novel lamellar coordination polymer incorporating partially overlapped helices,ladders and zigzag chains – Synthesis,crystal structure and magnetic property

The hydrothermal assembly of CoCl₂ · H₂O with benzene-1, 2, 3, 4-tetracarboxylic acid (H₄mpda) yielded a novel lamellar coordination polymeric complex, Co₂mpda(H₂O)₆ · H₂O (1), in which each layer presents an interesting multifold topology: both as partially overlapped helices with alternate chirality and as alternately arranged ladders and zigzag chains.     

Copper–cobalt heterobimetallic ceramic oxide thin film deposition: Synthesis,characterization and application of precursor

Thin films of halide free Cu–Co mixed metal oxide have been prepared at 390 °C from the heterobimetallic complex Co₄(THF)₄(TFA)₈(μ-OH)₂Cu₂(dmae)₂ · 0.5C₇H₈ (1) [dmae = N,N-dimethylaminoethanol ((CH₃)₂NCH₂CH₂O⁻), TFA = triflouroacetate (CF₃COO⁻), THF = tetrahydrofurane (C₄H₈O)] which was prepared by the reaction of [Cu(dmae)Cl]₄ and Co(TFA)₂ · 4H₂O. The precursor was characterized for its melting point, elemental composition, FTIR and X-ray single crystal structure determination. Thin films grown on glass substrate by using AACVD out of complex 1 were characterized by XRD and SEM. TGA and AACVD experiments reveal it to be a suitable precursor for the deposition of halide free Cu–Co mixed-metal oxide thin films at relatively low temperatures.     

Two organic–inorganic hybrid materials based on the penta-nuclear {MMn4} (M = W and Mo) heterometallic clusters and Schiff-base ligands

Two organic–inorganic hybrid compounds with the formula {[Mn^III(Salen)(H₂O)]₄MoO₄}·Cl₂·16H₂O (1) and {[Mn^III(Salen)(H₂O)]₄WO₄}·(CH₃COO)₂·11H₂O (2) (Salen = Di-[2-hydroxyl-3-methoxyl-benzaldehyde] ethylenediamine) have been synthesized and structurally characterized by IR, UV–vis spectroscopy, TG analysis and single crystal X-ray diffraction. Structural analysis revealed that compounds 1 and 2 consist of a [MoO₄]^2 − or [WO₄]^2 − building unit and four {[Mn^III(Salen)(H₂O)]⁺ metal–organic moieties, respectively. In the crystal structure, the [MoO₄]^2 − or [WO₄]^2 − tetrahedra coordinated with four Mn^III ions, resulting in the penta-nuclear heterometallic tetrahedra cluster compounds, which were rarely observed in the Mn-Salen system. Magnetic study revealed that there was antiferromagnetic coupling in the two compounds.     

K10[Co4(H2O)2(B-α-SiW9O34H)2] · 21H2O: A sandwich polyoxometalate based on the magnetically interesting element cobalt

The magnetism of a sandwich tetracobalt(II) substituted tungstosilicate K₁₀[Co₄(H₂O)₂(B-α-SiW₉O₃₄H)₂] · 21H₂O has been studied based on an isotropic Heisenberg model supplemented by a zero-field splitting term.     

Optimal synthesis and new understanding of P2-type Na2/3Mn1/2Fe1/4Co1/4O2 as an advanced cathode material in sodium-ion batteries with improved cycle stability

A sol-gel method with ethylene diamine tetraacetic acid and citric acid as co-chelates is employed for the synthesis of P2-type Na_2/3Mn_1/2Fe_1/4Co_1/4O₂ as cathode material for sodium-ion batteries. Among the various calcination temperatures, the Na_2/3Mn_1/2Fe_1/4Co_1/4O₂ with a pure P2-type phase calcined at 900 °C demonstrates the best cycle capacity, with a first discharge capacity of 157 mA h g^?1 and a capacity retention of 91 mA h g^?1 after 100 cycles. For comparison, the classic P2-type Na_2/3Mn_1/2Fe_1/2O₂ cathode prepared under the same conditions shows a comparable first discharge capacity of 150 mA h g^?1 but poorer cycling stability, with a capacity retention of only 42 mA h g^?1 after 100 cycles. Based on X-ray photoelectron spectroscopy, the introduction of cobalt together with sol-gel synthesis solves the severe capacity decay problem of P2-type Na_2/3Mn_1/2Fe_1/2O₂ by reducing the content of Mn and slowing down the loss of Mn on the surface of the Na_2/3Mn_1/2Fe_1/4Co_1/4O₂, as well as by improving the activity of Fe³⁺ and the stability of Fe⁴⁺ in the electrode. This research is the first to demonstrate the origin of the excellent cycle stability of Na_2/3Mn_1/2Fe_1/4Co_1/4O₂, which may provide a new strategy for the development of electrode materials for use in sodium-ion batteries.     

A new rhombic 2D interpenetrated organic-inorganic hybrid material base on [HxAs2Mo6O26](6 − x)− polyoxoanion and Co-btb complexes

The new compound based on unconventional arsenomolybdate: {Co(btb)(H₂O)₂}₂{H₂As₂Mo₆O₂₆}·2H₂O (btb = 1,4-bis(1,2,4-triazol-1-y1)butane) (1) has been hydrothermally synthesized and characterized by single-crystal X-ray diffraction analysis, elemental analyses, IR, XPS, UV–vis-NIR and TG. Compound 1 consists of [H₂As₂Mo₆O₂₆]^4 − polyoxoanion and {Co-btb} complexes, the polyoxoanion as a tetradentate node coordinated with the Co^2 + ions forming the rhombic 2D interpenetrated layer structure, which is further extended the 3D topological structure with symbol {4⁶ · 6² · 8¹⁶ · 12⁴}{4⁹ · 6⁶}²{4}² by weak interaction. It shows obvious photocatalytic activities for the degradation of methylene blue (MB) and rhodamine-B (RhB). In addition, the electrocatalytic activity upon the reduction of nitrite also has been studied.     

Three cobalt (II) complexes with triethylenetetraaminehexaacetic acid: From binuclear complex to 3d-4f coordination polymers

The cobalt(II)–lanthanide(III) heteronuclear complexes [Ln(H₂O)₄Co₂(TTHA)(SCN)₂]·H₃O⁺ (H₆TTHA = triethylenetetraaminehexaacetic acid, Ln = La(2), Ce(3)) have been synthesized based on a binuclear building block of [Co₂(H₂TTHA)(H₂O)₂] in [Co₂(H₂TTHA)(H₂O)₂]·4H₂O (1). Single-crystal structures show that complex 1 is a binuclear complex, containing the [Co₂(H₂TTHA)(H₂O)₂] unit as a useful building block. Adding the La^3 + and Ce^3 + ions to this synthesis system, two new 3d-4f mixed complexes 2 and 3 were obtained. Complexes 2 and 3 show 3D framework, comprising an infinite 1D (one-dimensional) chain based on heterometallic Ln₂Co₂ (Ln = La(2), Ce(3)). Further investigations such as IR spectra, UV–vis spectra, TGA, XRD and magnetic properties were studied.     

Hydrazine hydrate-induced hydrothermal synthesis of MnFe2O4 nanoparticles dispersed on graphene as high-performance anode material for lithium ion batteries

Herein, a MnFe₂O₄/graphene (MnFe₂O₄/G) nanocomposite has been synthesized via a facile N₂H₄·H₂O-induced hydrothermal method. During the synthesis, N₂H₄·H₂O is employed to not only reduce graphene oxide to graphene, but also prevent the oxidation of Mn²⁺ in alkaline aqueous solution, thus ensuring the formation of MnFe₂O₄/G. Moreover, MnFe₂O₄ nanoparticles (5–20 nm) are uniformly anchored on graphene. MnFe₂O₄/G electrode delivers a large reversible capacity of 768 mA h g⁻¹ at 1 A g⁻¹ after 200 cycles and high rate capability of 517 mA h g⁻¹ at 5 A g⁻¹. MnFe₂O₄/G holds great promise as anode material in practical applications due to the outstanding electrochemical performance combined with the facile synthesis strategy.