Two temperature-dependent 2D heterometallic Cd(II)–Dy(III) coordination polymers exhibiting slow magnetic relaxation and luminescence properties

Two unique two-dimensional (2D) Cd(II)–Dy(III) heterometallic coordination polymers, {[DyCd(HPMA)(PMA)₂(H₂O)₄]·2H₂O}_n (1) and [DyCd(PAA)(PMA)₂(H₂O)₃]_n (2, PAA^– = phenylacetate), were prepared successfully based on the phenylmalonic acid (H₂PMA). The construction of two polymers is sensitive to the reaction temperature and can be synthesized directionally at room temperature and 90 °C, respectively. Complexes 1 and 2 display 2D layer structures that include dinuclear [Dy₂] cluster node and Dy(III)-based 1D zigzag chain motif severally. The Dy(III)-based units in two structures both are spaced well with the adjacent ones by the diamagnetic Cd(II)-based moieties. The magnetic studies reveal that 1 and 2 both display slow magnetic relaxation with temperature-dependent relaxation peaks producing an effective energy barrier (Δτ) of 74.5 and 32.1 K, separately. Furthermore, the solid-state photophysical properties of 1 and 2 show strong characteristic luminescent emissions of Dy(III) ion in the visible region.     

Synthesis and Structure of Polynuclear Complex [La(bphsb)2(NO3)3]n

Ｓｏｍｅｌａｎｔｈａｎｉｄｅｃｏｍｐｌｅｘｅｓｗｉｔｈｄｉｓｕｌｆｏｘｉｄｅｓｈａｖｅｂｅｅｎｓｔｕｄｉｅｄ［１，２］．Ｈｏｗｅｖｅｒ，ｒｅｌａｔｉｖｅｌｙｌｉｔｌｅｗｏｒｋｈａｓｂｅｅｎｄｏｎｅｏｎｃｒｙｓｔａｌｓｔｒｕｃｔｕｒｅｏｆｔｈｅｓｅｃｏ...     

Synthesis of two lanthanide clusters LnIII4 (Gd4 and Dy4) with [2 × 2] square grid shape: Magnetocaloric effect and slow magnetic relaxation behaviors

Two isostructural tetranuclear lanthanide clusters named [Ln₄(L)₄(CH₃O)₄]·CH₃OH (Ln = Gd(III) for 1, Dy(III) for 2, H₂L = N′-(2-hydroxy-3-methoxybenzylidene)-6-(hydroxymethyl) picolinohydrazide) were successfully isolated by using a polydentate Schiff based ligand and Ln(III) nitrate salts. The structures of 1 and 2 were characterized by X-ray structural analyses, they are held by four double deprotonated ligands L²⁻. In them all the lanthanide ions are eight-coordinated and distributed over four vertices of a parallelogram, presenting a Ln₄ cluster with a strict [2 × 2] square grid pattern. The details of magnetic analysis show that 1 displays weak anti-ferromagnetic exchange between neighboring Gd(III) ions through carboxylate oxygen and methanol oxygen ligand atoms. Furthermore, 1 exhibits significant magnetocaloric effect with the maximum entropy change –ΔS_m value of 28.5 J/(kg·K) for ΔH = 7.0 T at 2.0 K. For compound 2, remarkable slow magnetic relaxation behaviors are observed in the presence of zero magnetic field with τ₀ = 1.02 × 10⁻⁶ s and energy barrier ΔE/k_B = 43.24 K.     

Anisotropic magnetocaloric effect in a dysprosium(III) single-molecule magnet — Commemorating the 100th anniversary of the birth of Academician Guangxian Xu

Dysprosium compounds with high magnetic anisotropy are widely studied as single molecule magnets (SMMs). Here the anisotropic magnetocaloric effect in a Dy(III) SMM, {[Dy(OSiMe₃)₂(4-Mepy)₅(BPh₄)] 0.5Toluene}, was studied by single crystals. Angular dependent magnetization can be observed at 300 K because of its high magnetic anisotropy. SMM behavior measured along the easy axis direction is identical to that of the polycrystalline sample. Rotating magnetization from the easy axis to the hard plane gives a maximum magnetic entropy change (–ΔS_R) of 3.05 J/(kg∙K) at 19 K at ΔB = 5 T, which enables the Dy(III) SMM to be used as a low-temperature rotating magnetic refrigerant.     

Electrochemical co-reduction of Y(III) and Al(III) in a fluoride molten salt system and electrolytic preparation of Y–Al intermediate alloys

In this study, a molten salt co-reduction method was proposed for preparing Y–Al intermediate alloys and the electrochemical co-reduction behaviors of Y(III) and Al(III) and the reaction mechanism of intermetallic compound formation were investigated by transient electrochemical techniques. The results show that the reduction of Y(III) at the Mo electrode is a reversible electrochemical process with a single-step transfer of three electrons, which is controlled by the mass transfer rate. The diffusion coefficient of Y(III) in the fluoride salt at a temperature of 1323 K is 5.0238 × 10^?3 cm²/s. Moreover, the thermodynamic properties associated with the formation of Y–Al intermetallic compounds were estimated using a steady-state electrochemical method. Y–Al intermediate alloy containing 92 wt% yttrium was prepared by constant current electrolysis at 1323 K in the LiF–YF₃–AlF₃–Y₂O₃ (6 wt%)–Al₂O₃ (1 wt%) system at a cathodic current density of 8 A/cm² for 2 h. The Y–Al intermediate alloy is mainly composed of α-Y₂Al and Y phases. The development and application of this innovative technology have solved major technical problems, such as a long production process, high energy consumption, and serious segregation of alloy elements at this stage.     

Synthesis and Crystal Structure of RE[CH_2(CH_2)_4CONC_4H_9]_3(NO_3)_3(RE=Dy,La)

ＳｙｎｔｈｅｓｉｓａｎｄＣｒｙｓｔａｌＳｔｒｕｃｔｕｒｅｏｆＲＥ［ＣＨ２（ＣＨ２）４ＣＯＮＣ４Ｈ９］３（ＮＯ３）３（ＲＥ＝Ｄｙ，Ｌａ）ＷａｎｇＨａｎｚｈａｎｇ（王汉章），ＸｕＱｉｎｇｆｅｎｇ（徐庆锋），ＱｉａｎＰｕ（钱朴）ＳｕｎＪｉａｎｐｉｎｇ（孙建...     

Conductivity of K_(10)H_3[Dy(SiW_4Mo_7O_(39))_2] Treated by Chemistry-Heated Diffusion of Sm and Gd Permeation

Inthelastfewyears ,theapplicationsofpolyox ometalates (POMs)havereceivedmuchattention[1～ 3]fortheiruniquestructuresandproperties ,however ,thepreparationofthemareallofsolid solidorliquid liquidreactions[1] .Fromtheknowledgeoffundamen taltheory ,wethinkthatrareearthelementscanbepermeatedintoPMOsthroughthesolid gasinterfacereaction ,andtoourknowledgethiskindofexperi menthasnotbeencarriedoutuntilnow .Inthispaper ,thechemistry heateddiffusedperme ationmethod[4 ] wasusedtotreatK10 H3[Dy(SiW4 M…     

Synthesis of two lanthanide clusters Ln_4~Ⅲ(Gd_4 and Dy_4) with [2×2] square grid shape:Magnetocaloric effect and slow magnetic relaxation behaviors

Two isostructural tetranuclear lanthanide clusters named [Ln_4(L)_4(CH_3 O)4]·CH_3 OH(Ln=Gd(Ⅲ) for 1,Dy(Ⅲ) for 2,H_2 L=N'-(2-hydroxy-3-methoxybenzylidene)-6-(hydroxymethyl) picolinohydrazide) were successfully isolated by using a polydentate Schiff based ligand and Ln(Ⅲ) nitrate salts.The structures of 1 and 2 were characterized by X-ray structural analyses,they are held by four double deprotonated ligands L~(2-).In them all the lanthanide ions are eight-coordinated and distributed over four vertices of a parallelogram,presenting a Ln4 cluster with a strict [2 × 2] square grid pattern.The details of magnetic analysis show that 1 displays weak anti-ferromagnetic exchange between neighboring Gd(Ⅲ) ions through carboxylate oxygen and methanol oxygen ligand atoms.Furthermore,1 exhibits significant magnetocaloric effect with the maximum entropy change-ΔS_m value of 28.5 J/(kg K) for ΔH=7.0 T at 2.0 K.For compound 2,remarkable slow magnetic relaxation behaviors are observed in the presence of zero magnetic field with τ_0=1.02 × 10~(-6) s and energy barrier ΔE/k_B=43.24 K.     

Monte Carlo simulations of segregation at [001] twist boundaries in a Pt(Au) alloy—I. Results

Monte Carlo simulations utilizing embedded atom method (EAM) potentials are used to study segregation of Au atoms—T = 850 to 1900K—to [001] twist boundaries in a Pt-1.0 at.% Au bicrystal containing ≈5000 atoms. The twist angle (θ) ranges from 0 to 45°. The average segregation factor (S_aver), defined as a ratio of the Au concentration in the two (002) planes which adjoin the interface over the bulk value, increase linearly as θ increases to ≈35°; S_aver decreases exponentially as T increases at each value of θ; the range of S_aver is ≈(1.2–3.5). No evidence is found for a systematic relationship between S_aver and the Σ value. The relationship between S_aver and θ is a result of the Au atoms segregating primarily substitutionally to the cores of pairs of orthogonal primary grain boundary dislocations (Part II).     

Influence of the substitution of Sm, Gd, and Dy for La in La_(0.7)Sr_(0.3)MnO_3 on its magnetic and electric properties and strengthening effect on room-temperature CMR

A series of La0.7–xSmxSr0.3MnO3, La0.7–xGdxSr0.3MnO3, and La0.7–xDyxSr0.3MnO3 (x=0.00, 0.10, 0.20, 0.30) samples were prepared by the solid-state reaction method. The influence of the substitution of Sm, Gd, and Dy for La on the magnetic and electric properties and on the magnetoresistance (MR) was studied through measurements of M-T curves and ρ-T curves. The results showed that: lattice distortion in-duced by substitution of Sm, Gd, and Dy for La and extra magnetism of substitution had great influence on the magnetic and electric proper-ties of perovskite manganites; substitution of magnetic rare earth element for La was an effective way to change Curie temperature and to strengthen MR in perovskite manganites; and appropriate substitution proportion would generate large MR near room temperature.     

Synthesis and Crystal Structure of a 4f-3d Complex [La(DMF)_6(H_2O)_3][Cr(CN)_6]·2H_2O

Ｒｅｃｅｎｔｌｙ ,ｔｈｅｒｅｈａｓｂｅｅｎｃｏｎｓｉｄｅｒａｂｌｅｉｎ ｔｅｒｅｓｔｉｎｌａｎｔｈａｎｉｄｅ(Ⅲ )ｈｅｘａｃｙａｎｏｆｅｒｒａｔｅｓａｎｄｔｈｅａｎａｌｏｇｏｕｓｃｏｂａｌｔ(Ⅲ )ａｓｗｅｌｌａｓｃｈｒｏｍｉｕｍ(Ⅲ )ｃｏｍｐｌｅｘｅｓｂｅｃａｕｓｅｏｆｔｈｅｉｒｐｏｔｅｎｔｉａｌａｓｃａｔａｌｙｔｉｃ ,ｓｅｍｉｃｏｎｄｕｃｔｉｖｅ ,ａｎｄｍａｇｎｅｔｉｃｍａｔｅ ｒｉａｌｓ[1～ 4] .Ｆｏｒｅｘａｍｐｌｅ ,ｍａｇｎｅｔｉｃｓｔｕｄｉｅｓｏｎａｓｅｒｉｅｓｏｆｔｈｒｅｅ ｄｉｍｅｎｓｉｏ…     

Influence of alkaline earth metal cations on the charge transfer kinetics for the redox couple Ti(IV)/Ti(III) in a chloride–fluoride melt

The influence of strongly polarizing cations Mg²⁺, Ca²⁺, Sr²⁺, and Ba²⁺ on the charge transfer kinetics of the redox couple Ti(IV)/Ti(III) is studied. The standard rate constants of charge transfer (k _s) for the Ti(IV)/Ti(III) redox couple in the (NaCl–KCl)_eq–NaF (10 wt %)–K₂TiF₆ melt upon the addition of the strongly polarizing cations into the starting melt are determined. The dependence of the charge transfer rate constants on the ionic potential of the cations is established. The activation energies of the charge transfer process are calculated for the fluoride complexes of the Ti(IV)/Ti(III) redox couple with the outer-sphere cations Mg²⁺, Ca²⁺, Sr²⁺, and Ba²⁺.     

Effect of the F–D Exchange Interaction on the Properties of Thin-Film Mdm Structures (M—Fe,Co, Ni; D—Tb2O3)

Powder Metallurgy and Metal Ceramics - The effect of f–d interaction on the current–voltage characteristics of metal–dielectric–metal (MDM) structures consisting of...     

Development of a Numerical Model for Simulating Transient Liquid Phase (TLP) Bonding Involving Two Solid–Liquid Interfaces that Concurrently Undergo 2D or 3D Migration

A new numerical model is developed for transient liquid phase (TLP) bonding involving two solid–liquid interfaces that concurrently undergo two-dimensional (2D) or three-dimensional (3D) migration in contrast to previous models in the literature where two solid–liquid interfaces are assumed to undergo one-dimensional (1D) migration. The developed model which incorporates variable diffusivity and conserves solute by using a unique hybrid explicit–fully implicit approach and an adaptable space discretization based on Murray–Landis transformation, respectively, is used to investigate the kinetics of the process and major predictions of the model are experimentally validated. It is found that in contrast to the case of 1D migration, despite matching material and bonding conditions, there is a transition from conventional symmetric solidification behavior to asymmetric solidification behavior such that the extent of isothermal solidification is consistently larger on the substrate in which curvature reduces along the direction of solute diffusion. Moreover, aside from what is generally known that the kinetics of isothermal solidification is controlled by diffusivity, equilibrium concentrations at the interface and initial substrate composition, this work shows that when the solid–liquid interface migrates in 2D or 3D, the kinetics is also significantly controlled by the type and degree of curvature at the migrating interface.