Search

An olivine-type orthothiophospate LiMnPS4 has been synthesized for the first time through a building block approach by reacting preformed ternary lithium thiophospate with MnCl2. Diffuse reflectance measurements show an optical band gap of 2.36 eV, which is further confirmed by DFT calculations. Irreversible weak ferromagnetic ordering and metamagnetism are verified through preliminary magnetic measurements.

Reactions of [Mn(H2 dapsc)Cl2 ]⋅H2 O (dapsc=2,6- diacetylpyridine bis(semicarbazone)) with K3 [Fe(CN)6 ] and (PPh4 )3 [Fe(CN)6 ] lead to the formation of the chain polymeric complex {[Mn(H2 dapsc)][Fe(CN)6 ][K(H2 O)3.5 ]}n ⋅1.5n H2 O (1) and the discrete pentanuclear complex {[Mn(H2 dapsc)]3 [Fe(CN)6 ]2 (H2 O)2 }⋅4 CH3 OH⋅3.4 H2 O (2), respectively. In the crystal structure of 1 the high-spin [MnII (H2 dapsc)]2+ cations and low-spin hexacyanoferrate(III) anions are assembled into alternating heterometallic cyano-bridged chains. The K+ ions are located between the chains and are coordinated by oxygen atoms of the H2 dapsc ligand and water molecules. The magnetic structure of 1 is built from ferrimagnetic chains, which are antiferromagnetically coupled. The complex exhibits metamagnetism and frequency-dependent ac magnetic susceptibility, indicating single-chain magnetic behavior with a Mydosh-parameter φ=0.12 and an effective energy barrier (Ueff /kB ) of 36.0 K with τ0 =2.34×10-11 s for the spin relaxation. Detailed theoretical analysis showed highly anisotropic intra-chain spin coupling between [FeIII (CN)6 ]3- and [MnII (H2 dapsc)]2+ units resulting from orbital degeneracy and unquenched orbital momentum of [FeIII (CN)6 ]3- complexes. The origin of the metamagnetic transition is discussed in terms of strong magnetic anisotropy and weak AF interchain spin coupling.

Hydrogen redistribution between the two magnetic states that coexist at transition temperature, which is called the splitting phenomenon, was investigated in La(Fe,Si)13-based magnetocaloric compounds. Asymmetric splitting into two portions with different volumes and H concentrations was observed on analysis of thermomagnetization curves, and this asymmetric growth was determined, using first-principle calculations, to be correlated with the electronic band structure. Excellent entropy change was observed in (Ce,La)(Fe,Mn,Si)13H specimens, on which full hydrogenation was performed to inhibit the splitting phenomenon. The splitting phenomenon was found to be incompletely suppressed in these specimens after a short duration of homogenization annealing, and it gradually disappeared with increasing annealing duration. Magneto-optical observation with a magnetic transfer film shows that first heterogeneous nucleation appears at the spot-like sites; this is followed by the instant growth of a cloud-shaped droplet. The pinning of the droplet boundary by the spot-like nucleation site was also confirmed. Comparison of the metallographic structure revealed that the spot-like heterogeneous nucleation sites correspond to the grain-boundary triple points formed by imperfect grains, which would be swallowed by other stable grains during a ripening action. The droplet boundary, which is central to the hydrogen diffusion process, runs inside of crystalline grains, and in consequence, the main diffusion path of hydrogen was considered to be the body diffusion.

The metamagnetic properties of the manganese magnesium ferrites having the general formula Mn0.7Mg0.3Fe2O4 prepared by the standard ceramic technique have been studied. It is proposed that when a change of temperature at adequate magnetic field is applied in a Mn0.7Mg0.3Fe2O4 a magnetic phase transition will be generated, giving rise to an antiferromagnetic (AFM) state from ferrimagnetic (FM) phase. The critical transition field H ac = 300 A/m was estimated for critical magnetization curve of transition from the metamagnetic behavior to FM behavior of sample. The FM to AFM transition in these ferrites is accompanied by a Néel type to Yafet-Kittel type transition and gradual spin ordering changes of the unit cell volume. The application of an external magnetic field to the low-temperatures AFM state causes the sample to reset to the original FM state.

Herein, we have synthesized at room-temperature two-dimensional nanosheets of a MOF comprised of cobalt(II) ion with benzenedicarboxylic acid ligand, which exhibited unusual magnetic properties. D...

application/pdf, Inorganic Chemistry. 2021, 60 (10), P.7023-7030

We report on crystal structure, magnetic and thermal physical properties of EuPd$_2$Sn$_4$ stannide. From the magnetic susceptibility measurements a divalent state of Eu rare earth element was determined together with an antiferromagnetic (AFM) order at 11 K. By applying magnetic field, the magnetic behavior variation reveals a complex magnetic structure. Above a critical field Bc a ferromagnetic (FM)-like character starts to prevail. AFM and FM regimes are separated by a metamagnetic region. Heat capacity measurements confirm this behavior.

Co-BDC ([Co2(OH)2BDC], H2BDC = 1,4-benzenedicarboxylic acid) is known to possess metamagnetism originating from the antiparallel spins and high magneto crystalline anisotropy of Co(II).1 Herein, we have introduced a bimetallic concept by incorporating Ni(II) along with Co(II) in the same coordination polymer to modulate the magneto crystalline anisotropy in the lattice which in turn, affects the overall magnetic response of the coordination polymer. The Curie-Weiss equation fit suggested antiparallel arrangement of the spins (θ ≈ -62.5 K) of Ni(II) and Co(II) arranged in alternate fashion. The cusp in magnetization was observed at 7 K (Tc) with a significant coercive field of ∼750 Oe at 5 K.

The solvo-thermal syntheses of [(CoSalphen)2Co (SCN)2]n (1), CoSalphen(NH3)(N3)(2), Na[CoIIIsalphen(N3)2](3), Na[CoIIIsalen(N3)2](4) and CoIIIsalen(NH3)(N3) (5) {salphen = N,N’-o-phenylene-bis(salicylideneimine)} are reported. The structural studies using X-ray diffraction measurements revealed that 1 crystalizes in a monoclinic C2/c space group. Two cobalt (II) metal centers in penta-coordinated and octahedral local coordination environments are bridged via alternating O and μ1,3 SCN bridges resulting in a novel 2D layered coordination polymer. Compound 2 is a trivalent mononuclear cobalt azido complex with an octahedral coordination environment. The magnetic investigations of 1 revealed ferromagnetic coupling (J = +49.1 cm−1) and meta-magnetic ordering. Time resolved photoluminescence studies of the complexes showed excited state lifetimes of (τ1 = 0.4675 ns, τ2 = 5.23 ns) for 1 and (τ1 = 0.5078 ns, τ2 = 6.79 ns) for 2.

This paper reports the magnetic properties of a series of isomorphous metal–organic frameworks based on random heterometallic Co1−xNix chains with simultaneous azide, carboxylate and tetrazolate bridges. All the mixed-metal compounds show intrachain FM interactions, field-induced metamagnetism, and SCM-like slow magnetic relaxation. These behaviors are quite different from the parent Co(II) and Ni(II) materials, and even a small amount of metal replacement can cause significant magnetic changes. The static properties such as AF ordering, metamagnetic critical field and the hysteresis parameters show complicated composition dependence. Most interestingly, the mixed-metal systems can show a higher blocking temperature than the Co(II) compound, suggesting that the randomly distributed metal ions have synergistic effects on slow relaxation of magnetization. This is phenomenologically associated with the competitive effects of Δτ and τo.

A series of isomorphous random bimetallic NiII-MnII compounds with N-methylpyridinium-4-carboxylate (4-mpc) and azide, have been synthesized and characterized. They are of formula [NiIIxMnII1−x(N3)2(4-mpc)] (1−6), (x = 1 (1), 0.86 (2), 0.83 (3), 0.71 (4), 0.56 (5), 0.47 (6)). Compounds 1–6 consist of one-dimensional uniform chains with [(μ-EO-N3)2(μ-COO)] triple bridges (EO = end-on). Magnetic measurements reveal that compounds 1–6 behave as antiferromagnets with a gradual ferromagnetic-to-antiferromagnetic evolution by the incorporating of isotropic MnII ions into NiII chain. The NiII-rich compounds 1–3 exhibit field-induced metamagnetism. And the TN of the heterometallic compounds exhibit a composition-dependence of the content of NiII.

We report the growth, structural and magnetic properties of the less studied Eu-oxide phase, Eu$_3$O$_4$, thin films grown on a Si/SiO$_2$ substrate and Si/SiO$_2$/graphene using molecular beam epitaxy. The X-ray diffraction scans show that highly-textured crystalline Eu$_3$O$_4$(001) films are grown on both substrates, whereas the film deposited on graphene has a better crystallinity than that grown on the Si/SiO$_2$ substrate. The SQUID measurements show that both films have a Curie temperature of about 5.5 K, with a magnetic moment of 0.0032 emu/g at 2 K. The mixed-valency of the Eu cations has been confirmed by the qualitative analysis of the depth-profile X-ray photoelectron spectroscopy measurements with the Eu$^{2+}$ : Eu$^{3+}$ ratio of 28 : 72. However, surprisingly, our films show no metamagnetic behaviour as reported for the bulk and powder form. Furthermore, the Raman spectroscopy scans show that the growth of the Eu$_3$O$_4$ thin films has no damaging effect on the underlayer graphene sheet. Therefore, the graphene layer is expected to retain its properties., 16 pages, 9 figures

The synthesis, crystal structure, and magnetic studies are reported for a two-dimensional network of mixed valence {Mn6} cages. The compound contains three different bridging ligands: pivalate, phenylphosphonate, and partially deprotonated triethanolamine. The result of using three bridging ligands is acomplex structure involving a {MnIII2MnII4} edge-sharing bitetrahedron that interlinks, forming a layered structure. Weak intercage interactions lead to a remarkably complicated magnetic behaviour, with a phase transition at 2.1 K leading to a canted antiferromagnetic state.

The equiatomic intermetallic compounds RE IrMg ( RE = Y, La-Nd, Sm, Gd-Tm) and RE RhMg ( RE = Y, Sm, Gd-Tm) were synthesized from the elements in sealed niobium ampoules in a high-frequency furnace and characterized based on X-ray powder data. LaIrMg and CeIrMg crystallize with the orthorhombic LaNiAl type structure ( Pnma ), while all other compounds adopt the TiNiSi type. The structures of YRhMg, GdRh 1.190(4) Mg 0.810(4) , DyRh 1.126(5) Mg 0.874(5) , LaIrMg, NdIr 1.033(2) Mg 0.967(2) and ErIr 1.059(3) Mg 0.941(3) were refined from single-crystal X-ray diffractometer data. The striking structural motifs of these phases are tricapped trigonal prisms around the transition metal atoms formed by RE and Mg. The two structure types differ in the connectivity pattern of the trigonal prisms. The rhodium (iridium) atoms build up three-dimensional [RhMg] and [IrMg] networks in which cavities are filled by the rare earth atoms. Temperature dependent magnetic susceptibility measurements on X-ray pure samples of NdIrMg, SmRhMg, GdRhMg, TbRhMg and DyRhMg show Curie-Weiss paramagnetism of the trivalent rare earth ions and magnetic ordering at low temperatures: T C = 9.5 K for NdIrMg and Neel temperatures of 10.0, 16.7, 10.6 and 11.3 K for SmRhMg, GdRhMg, TbRhMg and DyRhMg. TbRhMg and DyRhMg exhibit field-induced spin reorientations (metamagnetism).

Rapid materials discovery in inorganic chemistry should combine predictive computational tools with fast experimental syntheses. We apply such a tandem approach to explore the Ba–Ru–S phase space, where no ternary compounds are yet known to exist. Related ternary oxide ruthenates and ternary iron sulfides exhibit interesting electronic properties due to d-electron correlations, such as superconductivity, metamagnetism, and quantum phase transitions. We use a combination of evolutionary algorithms and density functional theory to inform traditional and in situ diffraction methods. In the course of our investigation, we find that convex hull constructions of the binary constituents inform interpretation of the ternary hull, which in this case has two compounds near thermodynamic stability. Our experimental study does not reveal formation of the candidates BaRu2S2 or BaRuS3, but it does provide the structure of a high-temperature polymorph of BaS2. This methodology can be exploited to study other ternary sys...

Two coordination polymers [Co2(TA)(4,4′-bipy)2(H2O)2]·H2O (1) and [Ni2(TA)(4,4′-bipy)2(H2O)4]·3H2O (2) were prepared by hydrothermal reactions of MCl2·6H2O (M = Co, Ni) with a V-shaped ligand TDPA (3,3′,4,4′-thiodiphthalic anhydride) and a I-shaped N-donor co-ligand (4,4′-bipy). They were characterized by elemental analyses, thermogravinetric analyses, and magnetic behavior. As is expected, TDPA hydrolyzes into the corresponding tetra-carboxylate acid H4TA (3,3′,4,4′-thiodiphthalic acid) during the reactions. Co2 dimer and Ni mononuclear center are connected into two-dimensional (2D) layers by H4TA and 4,4′-bipy bridge in 1 and 2, respectively. The most amazing feature is that 1 and 2 exhibit interesting spin-canting metamagnetism and weak ferromagnetic behavior, respectively, with the critical Neel temperature of TN =4 K for 1 and TN =13 K for 2, based on variable temperature magnetic susceptibility measurements. In low mono- or dinuclear metal system, such magnetic behaviors have rare been observed. Furthermore, complex 1 will be a potential metamagnet material.

The new lanthanum vanadium oxyselenides LaVSe2O, La5V3Se6O7, La5V3Se7O5, La7VSe5O7, and La13V7Se16O15 were synthesized in eutectic NaI/KI fluxes, and their crystal structures were determined using single-crystal and powder X-ray diffraction experiments. LaVSe2O and La5V3Se6O7 adopt known structure types, whereas La5V3Se7O5, La7VSe5O7, and La13V7Se16O15 crystallize in hitherto unknown structure types. The main building blocks of these compounds are chains of edge-sharing VSe6, VSe5O, and/or VSe4O2 octahedra, linked together by edge-sharing OLa4 and/or OLa3V tetrahedra forming fluorite-like ribbons. LaVSe2O, La5V3Se7O5, and La7VSe5O7 contain only V(III) ions, whereby La5V3Se6O7 and La13V7Se16O15 contain mixtures of either V(III)/V(IV) or V(III)/V(V) cations. Magnetic measurements indicate Curie–Weiss paramagnetism and magnetic ordering of the vanadium moments at low temperatures. More precisely, we observe antiferromagnetism for La5V3Se6O7, metamagnetism for La5V3Se7O5, ferromagnetism for La7VSe5O7 and a complex magnetic structure for La13V7Se16O15.

The reactions of NiII or CuII ions with N3− anions in the presence of templated diethyl or triethyl amines afford three new azido-bridged coordination polymers, namely, [Ni(N3)2(Deeda)] (1), (DeaH)[Cu3(N3)7] (2), and (TeaH)[Cu4(N3)9] (3), where Deeda, (DeaH)+ and (TeaH)+ represent N,N-diethylethane-1,2-diamine, diethylammonium and triethylammonium, respectively. Magnetic studies revealed that they exhibit metamagnetism, spin glass and canted ferromagnetism, respectively, induced by different coordination modes of the azide ligands.

One-dimensional spin chains featuring strong axial anisotropic magnetism are promising candidates for isolatable and miniatured information storage materials, the so-called single-chain magnets (SCMs). Here we show a mixed azido/carboxylato bridged metamagnetic iron(II) chain [Fe(N3)2(4-mpc)]n (4-mpc = N-methylpyridinium-4-carboxylate) with a large energy barrier of 150 K, a large remnant magnetization (1.55Nβ) and coercivity (1.7 T at 2 K) for homo-spin SCMs. Heat capacity and Mossbauer spectroscopy studies corroborate the intrinsic nature of SCM behavior regardless of weak interchain magnetic interactions, which lead to the coexistence of metamagnetism but not long-range magnetic ordering. Moreover, detailed magnetic investigations indicate that the system is not only within the “Ising limit” but also in the “finite-size” regime.

Most well-known metal–organic frameworks (MOFs) possessing the magnetic Ni2O2(CO2)2 chains, called Ni-MOF-74, have been investigated with regard to magnetic properties at open-metal sites. We prese...

Homochiral nanotubular metal phosphonates (R)-or (S)-[Fe(pemp)(H2O2)2] [pemp2− = (R)- or (S)-(1-phenylethylamino) methylphonate] are reported which are the first examples of metal–organic nanotubes combining chirality, metamagnetism and highly selective nitric oxide absorption in the same molecular composite.

The formation of long-range magnetic order at low temperatures was established in francisite—type compounds Cu3La(SeO3)2O2X (X = Br and Cl) through measurements of magnetic susceptibility, magnetization, specific heat and X-band electron spin resonance. The significantly enhanced critical index p = 1.0 ± 0.1 in Cu3La(SeO3)2Br and p = 0.8 ± 0.1 in Cu3La(SeO3)2Cl in the temperature dependence of the width of ESR signal evidence the reduced dimensionality of the kagome-type francisite’s magnetic subsystem. Under action of external magnetic field, the presumably non-collinear six-sublattices antiferromagnetic structure of these compounds experiences the first-order metamagnetic transformation. The B–T magnetic phase diagrams were established from the positions of singularities in temperature and field dependences of thermodynamic properties. Contrary to pristine mineral Cu3Bi(SeO3)2Cl, no signature of structural phase transition was detected.

Metal phosphonate chemistry has witnessed a rapid development during the past two decades. Numerous compounds have been synthesized which show new architectures and interesting physical or chemical properties. In this article, we focus on the 3d transition metal phosphonate clusters with single molecule magnet behavior; chain compounds with single chain magnet behavior; and layer or three-dimensional compounds with ferromagnetism, ferrimagnetism, canted antiferromagnetism, and metamagnetism. Finally, magnetic 3d metal phosphonates with multifunctions are also discussed.

Employing p-substituted benzoates with electron-withdrawing/electron-donating groups as coligands, four copper–azido compounds, [Cu1.5(p-NO2-benzoate)(N3)2(H2O)]n (1), [Cu(p-NO2-benzoate)(N3)(H2O)]n (2), [Cu(p-OH-benzoate)(N3)(H2O)]n·nH2O (3) and [Cu(p-CH3-benzoate)(N3)]n (4), have been hydrothermally synthesized and structurally charactierized by single crystal X-ray diffraction. Structural analysis reveals that all compounds are composed of mixed EO-azido and syn–syn carboxylato-bridged Cu-N3/COO chains. Compound 1 features the alternating triple-bridged (μ-EO-N3)(μ-COO)(μ-H2O) and the double-bridged (EO-N3)2 modes. Both of 2 and 3 display the triple-bridged fashion (μ-EO-N3)(μ-COO)(μ-H2O). While 4 exhibits the double-bridged mode (μ-EO-N3)(μ-COO). Based on hydrogen-bonding interactions, Cu–N3/COO chains in 1–3 are further connected to form 3D supramolecular frameworks. As for compound 4, there are not hydrogen-bonding interactions when the p-CH3 substituted benzoate is employed as coligand. These compounds show intrachain ferromagnetic performance and different bulk properties. Remarkably, 1 features metamagnetism from antiferromagnetism to ferrimagnetism, while 3 reveals long-range ferromagnetic ordering between Cu(II) ions. Magneto-structural correlation has been also investigated.

Using a semi-flexible quadritopic N-donor ligand, 5,5′-bipyrimidine (bpym), four new azide-based coordination polymers, {[Co2(bpym)(N3)4]·MeCN}n (1), [Co(bpym)(N3)2]n (2), [Mn(bpym)(N3)2]n (3) and {[Ni3(bpym)3(N3)6]·2H2O}n (4) were synthesized and structurally characterized. With bpym aciting as a planar μ4-bridging ligand, the resulting compound, 1, comprised a net-to-net 3D framework composed of two grid-like 44-subnets, Co(EE-N3)2-based and Co2(bpym)-based sheets, with a (4,6)-connected (42·64)(48·66·8)2 topology. Compound 2 adopted a 3D pillared-layer framework with a pts topology based on six-connected Co(II) centers and four-connected twisted μ4-bpym ligands, while compound 3 adopted a 3D pillared-layer structure with a bcu topology based on Co(EE-N3)2-based 44-layers and two-connected twisted μ2-bpym pillars. In contrast, compound 4 had a 2D layered structure composed of 1D Ni(II) chains with alternating double EE–N3 and double EO–N3 bridges in an EE–EE–EO sequence and two-connected bpym linkers. The magnetic properties of 1–4 were investigated. The findings indicate that 1 showed weak ferromagnetism due to spin-canted antiferromagnetism and long-range magnetic ordering with a critical temperature, TC = 12.6 K. In contrast, compound 2 exhibited weak ferromagnetism due to spin-canted antiferromagnetism and antiferromagnetic ordering. In compound 3, antiferromagnetic interactions dominated between the Mn(II) centers through the EE–N3 bridges. In compound 4, the antiferromagnetic and ferromagnetic interactions were transmitted through double EE–N3 and double EO–N3 bridges, respectively, resulting in an AF–AF–F topological ferrimagnetic Ni(II) chain. Furthermore, field-induced magnetic phase transitions of metamagnetism for 2 and 4 were also observed below TN = 3.6 K and 8.2 K, respectively.

Peculiar magnetic behavior was found for 1D-polymeric seven-coordinate pentagonal bipyramidal Fe(II) complex {[Fe(L)(μ1,3-N3)](ClO4)} n (1) with a pentadentate macrocyclic ligand L (3,12,18-triaza-6,9-dioxabicyclo[12.3.1]octadeca-1(18),14,16-triene) coordinated in the pentagonal equatorial plane and with end-to-end bridging azido ligands in axial positions. The static and dynamic magnetic data revealed that spin-canting in the 1D-chain of 1 results in the single-chain magnet (SCM) behavior with high spin-reversal energy barrier Ueff (Δτ) = 87.5 K, exhibiting magnetic hysteresis below 4 K and coexistence with the metamagnetism altogether resulting in weak 3D-ferromagnetic behavior. This is the first reported example of the exclusively azido-bridged homospin Fe(II)-based SCM.

A magnetic metal organic framework {[Cu(but-1,4-dc)0.5(N3)(H2O)]·H2O}n (MFUM-1(Cu)) (but-1,4-dc = butane-1,4-dicarboxylate) was synthesized and characterized structurally and magnetically. In MFUM-1(Cu), each CuII ion has a distorted octahedral geometry with an obvious Jahn–Teller distortion, where the coordination environment is composed of mixed EO-azido/aliphatic based carboxylate/H2O threefold bridges. These bridges extend the structure of MFUM-1(Cu) in two dimensions by covalent connectivity and form square-shaped channels. Also, a study was done to determine the effectiveness of sonochemical synthesis for the preparation of nano-sheets of MFUM-1(Cu) and subsequently the influence of particle size on physical properties such as magnetic behavior and thermal stability. The particles were characterized by elemental analyses, infrared spectroscopy (IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and powder X-ray diffraction (PXRD) analyses. The effects of parameters such as concentration, solvent, and reaction time on the size distribution, morphology, and yield of product were carefully studied. The magnetic properties of MFUM-1(Cu) and corresponding nano-structure were examined which indicated metamagnetism with strong intrachain ferromagnetic coupling versus the weak interchain antiferromagnetic coupling. Finally, the application of MFUM-1(Cu) in the separation of carbon dioxide from nitrogen and also from methane was theoretically investigated. High calculated selectivity of CO2 over N2 and CH4 reveals the potential application of MFUM-1(Cu) in practical systems of gas separation.

A series of isomorphous compounds of general formula [Co1–xNix(tzpo)(N3)(H2O)2]n·nH2O (x = 0, 0.19, 0.38, 0.53, 0.68, 0.84, and 1; tzpo = 4-(5-tetrazolate)pyridine-N-oxide) was prepared. The compounds consist of homometallic or heterometallic chains with simultaneous azide-tetrazolate bridges. The heterometallic systems feature random distribution of metal ions. All compounds across the series exhibit intrachain ferromagnetic coupling, interchain antiferromagnetic (AF) ordering, field-induced metamagnetic transition, and, except the Ni-only compound, single-chain magnetic dynamics. The AF ordering temperature, the metamagnetic critical field, and the relaxation parameters show different composition dependence. Notably, the blocking temperature for the Co-rich materials is higher than the Co-only compound, suggesting synergy between the randomly distributed Co(II) and Ni(II) ions in promoting slow relaxation. The results imply rich physics in the random mixed-metal systems and demonstrate the possibility o...

Two new three-dimensional (3D) Co(II)- and Cu(II)-azido frameworks, [Co2(N3)4(bpym)2]n (1) and [Cu2(N3)4(bpym)]n (2), were successfully synthesized by introducing a semi-flexible N-donor ligand, 5,5′-bipyrimidin (bpym), with different bridging modes and orientations. Compounds 1 and 2 were structurally characterized by X-ray crystallography, IR spectroscopy, thermogravimetry and elemental analysis. Compounds 1 and 2 are 3D pillared-layer frameworks with double end-on (EO) azido bridged dinuclear motifs, [M2(EO-N3)2]. In Compound 1, the bpym ligands show trans μ2-bridging mode and the role as pillars to connect the Co(II)-azido layers, composed of [Co2(EO-N3)2] motifs and single end-to-end (EE) azido bridges, to a 3D network with BN topology. In contrast, in 2, the bpym ligand adopts a twisted μ4-bridging mode, which not only connects the adjacent [Cu2(EO-N3)2] units to a layer, but also functions as a pillar for the layers of the 3D structure. The structural diversities between the two types of architectures can be attributed to the coordination geometry preference of the metal ions (octahedral for Co2+ and square pyramidal for Cu2+). Magnetic investigations revealed that Compound 1 exhibits ferromagnetic-like magnetic ordering due to spin canting with a critical temperature, TC = 33.0 K, and furthers the field-induced magnetic transitions of metamagnetism at temperatures below TC. Compound 2 shows an antiferromagnetic ordering with TN = 3.05 K and a field-induced magnetic transition of spin-flop at temperatures below the TN.

International audience; A new dinuclear complex [{Fe(tpc-OBn)(NCS)(μ-NCS)}2] (1) based on the tripodal tpc-OBn ligand (tpc-OBn = tris(2-pyridyl)benzyloxymethane), containing bridging μ-κN:κS-SCN and terminal κN-SCN thiocyanate ligands, has been prepared and characterized by single crystal X-ray diffraction, magnetic studies, and DFT theoretical calculations. This complex represents the first example of dinuclear FeII complex with double μ-κN:κS-SCN bridges in a head-to-tail configuration that exhibits ferromagnetic coupling between metal ions (JFeFe = +1.08 cm–1). Experimental and theoretical magnetostructural studies on this kind of infrequent FeII dinuclear complex containing a centrosymmetrically [Fe2(μ-SCN)2] bridging fragment show that the magnitude and sign of the magnetic coupling parameter, JFeFe, depend to a large extent on the Fe–N–C (α) angle, so that JFeFe decreases linearly when α decreases. The calculated crossover point below which the magnetic interactions change from ferromagnetic to antiferromagnetic is found at 162.3°. In addition, experimental results obtained in this work and those reported in the literature suggest that large Ntripodal–FeII distances and bent N-bound terminal κN-SCN ligands favor the high spin state of the FeII ions, while short Ntripodal–FeII distances and almost linear Fe–N–C angles favor a stronger ligand field, which enables the FeII ions to show spin crossover (SCO) behavior.

A three-dimensional metal-organic framework based, high-energy-density compound, [Co5(3-atrz)7(N3)3] (3-atrz = 3-amine-1H-1,2,4-triazole), features superior detonation properties, insensitivity, and thermostability. Magnetic studies show that the compound characterizes the coexistence of remarkable coercivity, metamagnetism, long-range ordering, and relaxation dynamics. The heat-capacity measurement confirms the typical long-range antiferromagnetic ordering below 16 K. This difunctional system exemplifies an effective attempt at developing advanced magnetoenergetic materials.

The 3D framework [Mn3(CH3COO)2(HCOO)4]n·nDMF (1) was obtained from the assembly of MnII ions with acetate and the in-situ generated formate ligands. It features Mn-centered MnMn4 tetrahedral nodes, each of which is linked to another four ones by sharing the apexes to form the 3D framework of 1. Each of the acetate and formate ligands behaves as a syn-syn:anti bridge to link two apical MnII ions and the central MnII ion. The magnetic measurement of 1 revealed the coexistence of spin-canted antiferromagnetism and metamagnetism. It represents a typical example to synergistically use two kinds of carboxylate ligands to construct metal-organic frameworks, as well as to tune the structure and magnetic properties of the aimed complex.

Hydro(solvo)thermal synthesis is a widely-used method to assemble various molecular magnetic materials based on different types of ligands. This review mainly focuses on the study of the magnetochemistry of azide/formate-mediated molecule-based magnetic materials of our lab synthesized under hydro(solvo)thermal conditions in the presence of coligand, with an emphasis on anionic coligand of carboxylate. The first section gives a brief discussion of azido and formato complexes and some important principles obtained from magneto-structural correlation; hydro(solvo)thermal synthetic strategies will also be referred to and elucidated in this part. The next six sections give overviews of the main results obtained in our group in recent years, that is, azide/formate-mediated ferromagnetism, ferrimagnetism, spin canting (or weak ferromagnetism), antiferromagnetism, single-molecule magnets (SMMs) and single-chain magnets (SCMs), and metamagnetism. Finally, the conclusions and perspectives of azido/formato-mediated molecular magnetic materials will be presented. Some of the trends identified could provide new insights into the further development of this promising area.

Three isostructural coordination polymers, M2(TZI)(OH)(H2O)2·xH2O (x = 3, M = Cu(II) 1, x = 4, M = Co(II) 2 and Ni(II) 3) (H3TZI = 5-(1H-tetrazol-5-yl)isophthalic acid), have been synthesized under hydrothermal conditions. The compounds consist of 3D frameworks, in which the magnetic Δ-chain motifs based on corner-sharing M3(μ3-OH) isosceles triangle are linked by the TZI ligands, and they represent the rare (3,4,5,6)-connected 4-nodal net topology with the point symbol (43)(4462)(4664)(4768). Magnetic analyses indicate that compound 1 shows the coexistence of spin canting, metamagnetism and antiferromagnetic ordering, whereas compounds 2 and 3 exhibit canted antiferromagnetic coupling without magnetic ordering down to 2 K. Such magnetic behaviors above 2 K are still rare in Cu(II), Co(II) and Ni(II) compounds with similar chains.

We herein report the syntheses, structures, and magnetic properties of two isostructural two-dimensional (2D) coordination polymers based on a pentagonal bipyramidal CoII unit [Co(TODA)]2+ and two hexacyanometallates, namely [MIII(CN)6]2[CoII(TODA)]3·9H2O (M = Cr (1), Co (2), TODA = 1,4,10-trioxa-7,13-diazacyclopentadecane). Structure analyses show that both complexes have 2D honeycomb structures where the [Co(TODA)]2+ units are bridged by the [MIII(CN)6]3− groups through three cyano groups in the facial positions. Magnetic investigation reveals ferromagnetic coupling between the CrIII and CoII centres through cyanides in 1. Due to the antiferromagnetic interaction between the layers, compound 1 exhibits an antiferromagnetic ordering below 11.4 K, and shows a metamagnetic phase transition under an external dc field. Due to the disorder of the TODA ligands, compound 1 shows a spin glass behavior, which leads to slow magnetic relaxation in 1. A butterfly-shaped hysteresis loop at 1.8 K can be observed with a coercive field of 720 Oe, which is quite large for cyano-bridged Cr–Co molecular magnets. For compound 2 containing the diamagnetic [CoIII(CN)6]3− unit, field-induced slow magnetic relaxation was also verified, which makes compound 2 a rare example of an SIM assembled in a 2D network. An easy-plane magnetic anisotropy with a positive D value (29.9 cm−1 by PHI and 26.5 cm−1 by Anisofit2.0) was deduced for hepta-coordinated CoII centers. These results show the efficiency of the strategy of combining cyanometallates and pentagonal bipyramidal precursors for novel molecular magnetic materials.

In this chapter, to obtain new ionic conductive magnetic material using octacyanometalate-based magnet, the incorporation of 4-aminopyridine as organic ligand is performed due to the capability of forming hydrogen bond. The reaction of MnII, [NbIV(CN)8], and 4-aminopyridine yielded yellow crystal formulated as Mn 3 II [NbIV(CN)8]2(4-aminopyridine)10(4-aminopyridinium)2 · 12H2O. This compound possesses non-coordinated pyridinium cation and 1-dimensional infinite hydrogen-bonding networks constructed with ligand water molecules, non-coordinated water molecules, and 4-aminopyridinium cations. Magnetic measurements revealed that the present compound shows metamagnetism with a Neel temperature of 9 K. The impedance measurement showed that the present compound exhibits super-ionic conductivity (>10−4 S cm−1) which is caused by proton conduction based on the Grotthuss mechanism. In the present material, 4-aminopyridinium cation is incorporated into the flexible octacyanidometallate-based magnetic framework and plays an important role in the formation of the hydrogen-bonding network, which leads to the observation of super-ionic conductivity.

It is a challenge to tune the magnetic properties of 1D complex via balancing the intra- and interchain magnetic interactions. Utilizing tricyanometalate precursors with different steric hindrance to react with CuII in the presence of 4-styrylpyridine or 4-cyanopyridine, respectively, two cyano-bridged {Fe2Cu} double-zigzag chains [FeIII(Tp)(CN)3]2CuII(4-styrylpyridine)2·3CH3CN·3H2O (Tp = hydrotris(pyrazolyl)borate) (1) and [FeIII(pzTp)(CN)3]2CuII(4-cyanopyridine)2·2CH3CN·H2O (pzTp = tetrakis(pyrazolyl)borate) (2) were obtained. 1 shows metamagnetism with a critical field of 700 Oe, whereas 2 shows the coexistence of metamagnetism and single-chain magnet behavior.

Two pairs of enantiomeric Co(II) compounds with formulas [Co2 (μ3 -OH)(cyamp)(Cn H2n+1 COO)] (cyampH2 =(S)- or (R)-[(1-cyclohexylethyl)amino]methylphosphonic acid; n=1 (1); n=7 (2)) were synthesized. The structures of S-1 and S-2 were determined by single-crystal structural analyses. Both crystallize in a monoclinic chiral space group P21 , and exhibit layered structures in which the Δ-type chains of corner-sharing Co3 (μ3 -OH) triangles are connected by the phosphonate groups. The interlayer spaces are filled with the organic groups of the phosphonate and carboxylate ligands. Therefore, the distances between the layers can be manipulated by the length of the alkyl chain of the carboxylate ligands, from 14.6 Å in 1 to 20.0 Å in 2. Magnetic studies were carried out for compounds S-1 and S-2. Both show metamagnetism at low temperature. The critical field decreases with increasing interlayer distance from 8.18 kOe for S-1 to 7.01 kOe for S-2 at 1.8 K. The optical properties were also studied.

This Paper reports the first examples of O-P-O bridged Mn2(salen)2 (salen = N,N'-bis(salicylidene)ethylenediamine) chain compounds, namely, [Mn2(salen)2(2-FC6H4PO3H)](ClO4)·1/2CH3OH (1) and [Mn2(salen)2(4-FC6H4PO3H)](ClO4) (2). The phosphonate ligands adopt a syn-anti bidentate bridging mode in 1 and a syn-syn bidentate bridging mode in 2, originated from the isomeric phosphonate ligands. The different bridging modes cause a significant change in the Mn-O···O-Mn torsion angle over the O-P-O bridge, which are 96.6 and 1.9° for 1 and 2, respectively. As a result, the antiferromagnetic (AF) exchange couplings mediated through the O-P-O pathway are extremely weak in 1, and the overall magnetic behaviors are dominated by the Mn2(salen)2 moieties. Single-molecule magnetic behavior is observed in 1. For compound 2, the AF interaction over the O-P-O bridge is much stronger. The coexistence of metamagnetism and single-chain magnetic behavior is observed for 2.

The quinary members of the complex boride series Sc2FeRu5–xIrxB2 were synthesized by arc melting the elements and characterized by powder and single-crystal X-ray diffraction as well as metallographic and energy-dispersive X-ray analyses. The use of a 4d/5d mixture allows distinguishing these elements with X-ray diffraction methods, thus enabling the study of site preference and its influence on the magnetic properties.The magnetic measurements reveal several changes of magnetic ordering within the series: from antiferromagnetism (Sc2FeRu5B2) to ferromagnetism (Sc2FeRuIr4B2) and finally to metamagnetism (Sc2FeIr5B2). Within the quinary series, the magnetic moments continuously increase with increasing amounts of Ir in one (8j) of two possible Wyckoff sites. The members with x = 2 and 3 represent the first hard magnetic borides of transition metals.

The self-assembly of Ru2(CO3)43− paddle-wheel precursors and Mn2+ ions in aqueous solution yields various carbonate complexes. With appropriate selection of the synthetic conditions, we are able to intentionally tune the composition and structure of Mn–Ru2-carbonate assemblies to form infinite chain structural complexes, e.g., K[{Mn(H2O)4}2Ru2(CO3)4Br2]·H2O (1) and H[{Mn(H2O)4}2Ru2(CO3)4Br2]·6H2O (2). Complexes 1 and 2 are obtained at different temperatures (25 °C for 1 and 5 °C for 2, respectively), and their crystal structures consist of brick-wall stacked chains, in which neighboring Ru2(CO3)4Br25− units are linked by two disubstituted octahedral Mn(H2O)42+ in a cis manner, resulting in two isomeric (twisted and zigzag) negative double-chain α- and β-{[Mn(H2O)4]2Ru2(CO3)4Br2}nn−. The magnetic properties of complexes 1 and 2 were highly characterized. The alternating current (AC) susceptibility analysis of complex 1 reveals a two-step magnetism transition at T1 = 5.0 K and T2 = 2.6 K, respectively. Complex 2 exhibits metamagnetism behavior, with a transition field HC = ∼1.2 kOe at 2.0 K.

Inconceivably large changes (up to 106%) of the resistivity induced by external magnetic field—a phenomenon known as the extreme magnetoresistance effect has been reported in a great number of exotic semimetals. The very recent and exciting discoveries mainly pay attention to the compounds without magnetic ground states, which appears to limit the potential growth of semimetal family. For fundamental scientific interests, introduction of spin degree of freedom would provide an almost ideal platform for investigating the correlation effect between magnetism, crystallographic structure and electric resistivity in materials. Here, we report the experimental observation of metamagnetic behaviors and transport properties of HoBi single crystals. Being a magnetic member of the rare earth monopnictide family, the magnetoresistance of HoBi is significantly modulated by the magnetic orders at low temperature, which shows a nonmonotonic increment across the successive magnetic phases and reaches 104% (9 T and 2 K) in the ferromagnetic state. Kohler’s rule predicts that more than one type of carriers dominates the transport properties. Well fitted magnetoresistance and Hall resistivity curves by the semiclassical two-band model suggest that the densities of electron and hole carriers are nearly compensated and the carrier mobilities in this compound are ultrahigh. Besides, the inverted band structures and nonzero Z 2 topological invariant indicate that possible nontrivial electronic states could generate in the ferromagnetic phase of HoBi. Combining the experimental and theoretical results, it is found that the cooperative action of carrier compensation effect and ultrahigh mobility might contribute to the extreme magnetoresistance observed in the titled compound. These findings suggest a paradigm for obtaining the extreme magnetoresistance in magnetic compounds and are relevant to understand the rare-earth-based correlated topological materials.

In order to investigate the magnetic properties of the solid solution CePt1–xPdxAl the individual compounds were synthesized from the elements using an arc furnace. From x = 0–0.8 the solid solution crystallizes in the orthorhombic TiNiSi-type structure (Pnma, no. 62; a = 721–722, b = 448–453 and c = 778–779 pm) and for x = 0.9 both the TiNiSi- as well as the hexagonal ZrNiAl-type structures were observed. The solid solution exhibits an interesting magnetic behavior as for small values of x ferromagnetic ordering can be found. At higher palladium content this changes towards an antiferromagnetic ordering. Furthermore the solid solution exhibits a spin-reorientation (meta-magnetic step) for x = 0.2–0.7.

A two-dimensional manganese-octacyanoniobate based magnet, MnII3[NbIV(CN)8]2(4-aminopyridine)10(4-aminopyridinium)2·12H2O, was prepared. This compound shows a spin-flip transition with a critical magnetic field value of ca. 200 Oe, which originates from metamagnetism. In addition, an impedance measurement indicates that this compound is a super-ionic conductor with 4.6 × 10–4 S cm–1. The observed super-ionic conductivity is explained by the proton conduction (so-called the Grotthuss mechanism) through the hydrogen-bonding network, i.e., Lewis acidity of the Mn ion accelerates the deprotonation of the ligand water molecules, and then the released proton propagates via ligand water molecules, noncoordinated water molecules, and 4-aminopyridinium cations.

Reaction of Co(NCS)2 with 1,2-bis(2-pyridyl)ethylene (2-bpe) leads to four new coordination compounds of composition [Co(NCS)2(CH3OH)4]·2(2-bpe) solvate (1), Co(NCS)2(2-bpe)2(CH3OH)2 (2), Co(NCS)2(2-bpe)2 (3) and Co(NCS)2(2-bpe) (4). The crystal structure of compounds 1 and 2 consists of discrete complexes in which the cobalt(II) cations are octahedral coordinated by two terminal thiocyanato anions and four methanol molecules in 1 and by two terminal N-bonded thiocyanato anions, two 2-bpe ligands and two methanol molecules in 2. In compound 3 also discrete complexes are found but in contrast to 1 and 2 each cobalt(II) cation is tetrahedral coordinated by two terminal N-bonded thiocyanato anions and two 1,2-bis(2-pyridyl)ethylene (2-bpe) ligands. In the most 2-bpe deficient compound 4 the Co cations are also tetrahedral coordinated but the metal cations are linked into chains by the 2-bpe ligands. Magnetic measurements on compound 3 shows only Curie–Weiss paramagnetism whereas for compound 4 a metamagnetic transition is observed at a critical field of HC = 1.9 kOe with antiferromagnetic ordering below and saturated paramagnetism above HC. These results are compared with those for the corresponding compound with 1,2-bis(4-pyridyl)ethylene as ligand.

In the course of studying the R 3 Pt 23 Si 11 series (R=rare earth), we have recently synthesized Nd 3 Pt 23 Si 11 . It crystallizes in a face-centered cubic structure ( Fm-3m space group) with a lattice parameter of 16.8493(4) A at room temperature. Heat capacity and magnetic measurements show the existence of a magnetic transition at 1.6 K. Measurements of the susceptibility and magnetization down to 95 mK reveal metamagnetic behavior confirming antiferromagnetic ordering. Powder neutron diffraction experiments show that the magnetic propagation vector is k =[000] and that the 6 neodymium moments in the unit cell are antiferromagnetically coupled in pairs.

Magnetic properties of DyAl$_{0.926}$Cr$_{0.074}$O$_3$ and DyAlO$_3$ were studied. We found that both compounds are antiferromagnetic with a low N\'eel transition temperature. At higher temperatures the magnetic characteristics show a Curie-Weiss dependence. The N\'eel temperature disappears when a field of about 2 T is applied, the system changes from an antiferromagnetic to a weak ferromagnetic behavior due to a metamagnetic transition. Furthermore, AC magnetic measurements in the Cr doped compound, at different frequencies, show a spin glass-like behavior. These transitions were studied and corroborated by specific heat measurements. We found the presence of metamagnetism and spin glass in the compound doped with chromium, determining that the small addition of chromium atoms modifies the magnetic properties of the compound DyAlO$_3$, resulting in new features such as the spin glass-like behavior., Comment: 7 pages, 8 figures, accepted in Journal of Materials Science