Thermal Hysteresis in a Spin-Crossover Fe^III Quinolylsalicylaldimine Complex, Fe^III(5-Br-qsal)₂Ni(dmit)₂·solv: Solvent Effects

The Fe^III complexes Fe­(5-Br-qsal)₂Ni­(dmit)₂·solv with solv = CH₂Cl₂ (<b>1</b>) and (CH₃)₂CO (<b>2</b>) were synthesized, and their structural and magnetic properties were studied. While magnetization and Mössbauer spectroscopy data of <b>1</b> showed a gradual spin transition, compound <b>2</b> evidenced an abrupt transition with a thermal hysteresis of 13 K close to room temperature (<i>T</i>_1/2 ↓ ∼273 K and <i>T</i>_1/2 ↑ ∼286 K). A similar packing arrangement of segregated layers of cations and anions was found for <b>1</b> and <b>2</b>. In both low-spin, LS, structures there are a large number of short intra- and interchain contacts. This number is lower in the high-spin, HS, phases, particularly in the case of <b>1</b>. The significant loss of strong π–π interactions in the cationic chains and short contacts in the anionic chains in the HS structure of <b>1</b> leads to alternating strong and weak bonds between cations along the cationic chains and the formation of unconnected dimers along the anionic chains. This is consistent with a significant weakening of the extended interactions in <b>1</b>. On the other hand, in the HS phase of <b>2</b> the 3D dimensionality of the short contacts observed in the LS phases is preserved. The effect of distinct solvent molecules on the intermolecular spacings explains the different spin crossover behaviors of the title compounds

[Fe(nsal₂trien)]SCN, a New Two-Step Iron(III) Spin Crossover Compound, with Symmetry Breaking Spin-State Transition and an Intermediate Ordered State

We report the synthesis of the iron­(III) complex of the hexadentate Schiff base ligand nsal₂trien obtained from the condensation of triethylenetetramine and 2 equiv. of 2-hydroxy-1-naphthaldehyde. The study of the salt [Fe­(nsal₂trien)]­SCN (<b>1</b>) by magnetic susceptibility measurements and Mössbauer spectroscopy reveals a rather unique behavior that displays thermally induced spin crossover (SCO) with two well-separated steps at 250 (gradual transition) and 142 K (steep transition). Single crystal X-ray structures were obtained at 294, 150, and 50 K, for the high spin (HS), intermediate (Int), and low spin (LS) phases. The HS and LS phases are isostructural, and based on a single Fe^III site (either HS or LS) an unusual symmetry break occurs in the transition to the Int ordered phase, where the unit cell includes two distinct Fe^III sites and is based on a repetition of the [HS–LS] motif. The two-step SCO behavior of <b>1</b> must result from the existence of structural constraints preventing the full conversion HS ↔ LS in a single step

Hybrid Magnetic Superconductors Formed by TaS₂ Layers and Spin Crossover Complexes

The restacking of charged TaS₂ nanosheets with molecular counterparts has so far allowed for the combination of superconductivity with a manifold of other molecule-intrinsic properties. Yet, a hybrid compound that blends superconductivity with spin crossover switching has still not been reported. Here we continue to exploit the solid-state/molecule-based hybrid approach for the synthesis of a layered TaS₂-based material that hosts Fe²⁺ complexes with a spin switching behavior. The chemical design and synthetic aspects of the exfoliation/restacking approach are discussed, highlighting how the material can be conveniently obtained in the form of highly oriented easy-to-handle flakes. Finally, proof of the presence of both phenomena is provided by the use of a variety of physical characterization techniques. The likely sensitivity of the intercalated Fe²⁺ complexes to external stimuli such as light opens the door for the study of synergistic effects between the superconductivity and the spin crossover switching at low temperatures

Selective Carbon Dioxide Hydrogenation Driven by Ferromagnetic RuFe Nanoparticles in Ionic Liquids

CO₂ is selectively hydrogenated to HCO₂H or hydrocarbons (HCs) by RuFe nanoparticles (NPs) in ionic liquids (ILs) under mild reaction conditions. The generation of HCO₂H occurs in ILs containing basic anions, whereas heavy HCs (up to C₂₁ at 150 °C) are formed in the presence of ILs containing nonbasic anions. Remarkably, high values of TONs (400) and a TOF value of 23.52 h^–1 for formic acid with a molar ratio of 2.03 per BMI·OAc IL were obtained. Moreover, these NPs exhibited outstanding abilities in the formation of long-chain HCs with efficient catalytic activity (12% conversion) in a BMI·NTf₂ hydrophobic IL. The IL forms a cage around the NPs that controls the diffusion/residence time of the substrates, intermediates, and products. The distinct CO₂ hydrogenation pathways (HCO₂H or FT via RWGS) catalyzed by the RuFe alloy are directly related to the basicity and hydrophobicity of the IL ion pair (mainly imposed by the anion) and the composition of the metal alloy. The presence of Fe in the RuFe alloy provides enhanced catalytic performance via a metal dilution effect for the formation of HCO₂H and via a synergistic effect for the generation of heavy HCs

Comparison of the performance of Skin Prick, ImmunoCAP, and ISAC tests in the diagnosis of patients with allergy

Background: Allergy is diagnosed from typical symptoms, and tests are performed to incriminate the suspected precipitant. Skin prick tests (SPTs) are commonly performed, inexpensive, and give immediate results. Laboratory tests (ImmunoCAP) for serum allergen-specific IgE antibodies are usually performed more selectively. The immuno-solid phase allergen chip (ISAC) enables testing for specific IgE against multiple allergen components in a multiplex assay. Methods: We retrospectively analysed clinic letters, case notes, and laboratory results of 118 patients attending the National Adult Allergy Service at the University Hospital of Wales who presented diagnostic difficulty, to evaluate which testing strategy (SPT, ImmunoCAP, or ISAC) was the most appropriate to use to confirm the diagnosis in these complex patients, evaluated in a “real-life” clinical service setting. Results: In patients with nut allergy, the detection rates of SPTs (56%) and ISAC (65%) were lower than those of ImmunoCAP (71%). ISAC had a higher detection rate (88%) than ImmunoCAP (69%) or SPT (33%) in the diagnosis of oral allergy syndrome. ImmunoCAP test results identified all 9 patients with anaphylaxis due to wheat allergy (100%), whereas ISAC was positive in only 6 of these 9 (67%). Conclusions: In this difficult diagnostic group, the ImmunoCAP test should be the preferred single test for possible allergy to nuts, wheat, other specific foods, and anaphylaxis of any cause. In these conditions, SPT and ISAC tests give comparable results. The most useful single test for oral allergy syndrome is ISAC, and SPT should be the preferred test for latex allergy

Stimuli Responsive Hybrid Magnets: Tuning the Photoinduced Spin-Crossover in Fe(III) Complexes Inserted into Layered Magnets

The insertion of a [Fe­(sal₂-trien)]⁺ complex cation into a 2D oxalate network in the presence of different solvents results in a family of hybrid magnets with coexistence of magnetic ordering and photoinduced spin-crossover (LIESST effect) in compounds [Fe^III(sal₂-trien)]­[Mn^IICr^III(ox)₃]·CHCl₃ (<b>1·CHCl</b>_<b>3</b>), [Fe^III(sal₂-trien)]­[Mn^IICr^III(ox)₃]·CHBr₃ (<b>1·CHBr</b>_<b>3</b>), and [Fe^III(sal₂-trien)]­[Mn^IICr^III(ox)₃]·CH₂Br₂ (<b>1·CH</b>_<b>2</b><b>Br</b>_<b>2</b>). The three compounds crystallize in a 2D honeycomb anionic layer formed by Mn^II and Cr^III ions linked through oxalate ligands and a layer of [Fe­(sal₂-trien)]⁺ complexes and solvent molecules (CHCl₃, CHBr₃, or CH₂Br₂) intercalated between the 2D oxalate network. The magnetic properties and Mössbauer spectroscopy indicate that they undergo long-range ferromagnetic ordering at 5.6 K and a spin crossover of the intercalated [Fe­(sal₂-trien)]⁺ complexes at different temperatures <i>T</i>_1/2. The three compounds present a LIESST effect with a relaxation temperature <i>T</i>_LIESST inversely proportional to <i>T</i>_1/2. The isostructural paramagnetic compound, [Fe^III(sal₂-trien)]­[Zn^IICr^III(ox)₃]·CH₂Cl₂ (<b>2·CH</b>_<b>2</b><b>Cl</b>_<b>2</b>) was also prepared. This compound presents a partial spin crossover of the inserted Fe^III complex as well as a LIESST effect. Finally, spectroscopic characterization of the Fe^III doped compound [Ga_0.99Fe_0.01(sal₂trien)]­[Mn^IICr^III(ox)₃]·CH₂Cl₂ (<b>3·CH</b>_<b>2</b><b>Cl</b>_<b>2</b>) shows a gradual and complete thermal spin crossover and a LIESST effect on the isolated Fe^III complexes. This result confirms that cooperativity is not a necessary condition to observe the LIESST effect in an Fe^III compound

Stimuli Responsive Hybrid Magnets: Tuning the Photoinduced Spin-Crossover in Fe(III) Complexes Inserted into Layered Magnets

The insertion of a [Fe­(sal₂-trien)]⁺ complex cation into a 2D oxalate network in the presence of different solvents results in a family of hybrid magnets with coexistence of magnetic ordering and photoinduced spin-crossover (LIESST effect) in compounds [Fe^III(sal₂-trien)]­[Mn^IICr^III(ox)₃]·CHCl₃ (<b>1·CHCl</b>_<b>3</b>), [Fe^III(sal₂-trien)]­[Mn^IICr^III(ox)₃]·CHBr₃ (<b>1·CHBr</b>_<b>3</b>), and [Fe^III(sal₂-trien)]­[Mn^IICr^III(ox)₃]·CH₂Br₂ (<b>1·CH</b>_<b>2</b><b>Br</b>_<b>2</b>). The three compounds crystallize in a 2D honeycomb anionic layer formed by Mn^II and Cr^III ions linked through oxalate ligands and a layer of [Fe­(sal₂-trien)]⁺ complexes and solvent molecules (CHCl₃, CHBr₃, or CH₂Br₂) intercalated between the 2D oxalate network. The magnetic properties and Mössbauer spectroscopy indicate that they undergo long-range ferromagnetic ordering at 5.6 K and a spin crossover of the intercalated [Fe­(sal₂-trien)]⁺ complexes at different temperatures <i>T</i>_1/2. The three compounds present a LIESST effect with a relaxation temperature <i>T</i>_LIESST inversely proportional to <i>T</i>_1/2. The isostructural paramagnetic compound, [Fe^III(sal₂-trien)]­[Zn^IICr^III(ox)₃]·CH₂Cl₂ (<b>2·CH</b>_<b>2</b><b>Cl</b>_<b>2</b>) was also prepared. This compound presents a partial spin crossover of the inserted Fe^III complex as well as a LIESST effect. Finally, spectroscopic characterization of the Fe^III doped compound [Ga_0.99Fe_0.01(sal₂trien)]­[Mn^IICr^III(ox)₃]·CH₂Cl₂ (<b>3·CH</b>_<b>2</b><b>Cl</b>_<b>2</b>) shows a gradual and complete thermal spin crossover and a LIESST effect on the isolated Fe^III complexes. This result confirms that cooperativity is not a necessary condition to observe the LIESST effect in an Fe^III compound

Stimuli Responsive Hybrid Magnets: Tuning the Photoinduced Spin-Crossover in Fe(III) Complexes Inserted into Layered Magnets

The insertion of a [Fe­(sal₂-trien)]⁺ complex cation into a 2D oxalate network in the presence of different solvents results in a family of hybrid magnets with coexistence of magnetic ordering and photoinduced spin-crossover (LIESST effect) in compounds [Fe^III(sal₂-trien)]­[Mn^IICr^III(ox)₃]·CHCl₃ (<b>1·CHCl</b>_<b>3</b>), [Fe^III(sal₂-trien)]­[Mn^IICr^III(ox)₃]·CHBr₃ (<b>1·CHBr</b>_<b>3</b>), and [Fe^III(sal₂-trien)]­[Mn^IICr^III(ox)₃]·CH₂Br₂ (<b>1·CH</b>_<b>2</b><b>Br</b>_<b>2</b>). The three compounds crystallize in a 2D honeycomb anionic layer formed by Mn^II and Cr^III ions linked through oxalate ligands and a layer of [Fe­(sal₂-trien)]⁺ complexes and solvent molecules (CHCl₃, CHBr₃, or CH₂Br₂) intercalated between the 2D oxalate network. The magnetic properties and Mössbauer spectroscopy indicate that they undergo long-range ferromagnetic ordering at 5.6 K and a spin crossover of the intercalated [Fe­(sal₂-trien)]⁺ complexes at different temperatures <i>T</i>_1/2. The three compounds present a LIESST effect with a relaxation temperature <i>T</i>_LIESST inversely proportional to <i>T</i>_1/2. The isostructural paramagnetic compound, [Fe^III(sal₂-trien)]­[Zn^IICr^III(ox)₃]·CH₂Cl₂ (<b>2·CH</b>_<b>2</b><b>Cl</b>_<b>2</b>) was also prepared. This compound presents a partial spin crossover of the inserted Fe^III complex as well as a LIESST effect. Finally, spectroscopic characterization of the Fe^III doped compound [Ga_0.99Fe_0.01(sal₂trien)]­[Mn^IICr^III(ox)₃]·CH₂Cl₂ (<b>3·CH</b>_<b>2</b><b>Cl</b>_<b>2</b>) shows a gradual and complete thermal spin crossover and a LIESST effect on the isolated Fe^III complexes. This result confirms that cooperativity is not a necessary condition to observe the LIESST effect in an Fe^III compound

Investigation of Charge-Ordered Barium Iron Fluorides with One-Dimensional Structural Diversity and Complex Magnetic Interactions

Three mixed-valence barium iron fluorides, Ba7Fe7F34, Ba2Fe2F9, and BaFe2F7, were prepared through hydrothermal redox reactions. The characteristic structures of these compounds feature diverse distributions of FeIIF6 octahedra and FeIIIF6 groups. Ba7Fe7F34 contained one-dimensional infinite ∞[FeIIFeIII6F34]14– double chains, comprising cis corner-sharing octahedra along the b direction; Ba2Fe2F9 contained one-dimensional ∞[Fe2F9]4– double chains, consisting of cis corner-sharing octahedra along the chain (a-axis direction) and trans corner-sharing octahedra vertical to the chain, while BaFe2F7 revealed three-dimensional (3D) frameworks that consist of isolated edge-sharing dinuclear FeII2F10 units linked via corners by FeIIIF6 octahedra. Magnetization and Mössbauer spectroscopy measurements revealed that Ba7Fe7F34 exhibits an antiferromagnetic phase transition at ∼11 K, where ferrimagnetic ∞[FeIIFeIII6F34]14– double chains are arranged in a paralleling manner, while Ba2Fe2F9 shows canted antiferromagnetic ordering at ∼32.5 K, leading to noncollinear spin ordering

Stimuli Responsive Hybrid Magnets: Tuning the Photoinduced Spin-Crossover in Fe(III) Complexes Inserted into Layered Magnets

The insertion of a [Fe­(sal₂-trien)]⁺ complex cation into a 2D oxalate network in the presence of different solvents results in a family of hybrid magnets with coexistence of magnetic ordering and photoinduced spin-crossover (LIESST effect) in compounds [Fe^III(sal₂-trien)]­[Mn^IICr^III(ox)₃]·CHCl₃ (<b>1·CHCl</b>_<b>3</b>), [Fe^III(sal₂-trien)]­[Mn^IICr^III(ox)₃]·CHBr₃ (<b>1·CHBr</b>_<b>3</b>), and [Fe^III(sal₂-trien)]­[Mn^IICr^III(ox)₃]·CH₂Br₂ (<b>1·CH</b>_<b>2</b><b>Br</b>_<b>2</b>). The three compounds crystallize in a 2D honeycomb anionic layer formed by Mn^II and Cr^III ions linked through oxalate ligands and a layer of [Fe­(sal₂-trien)]⁺ complexes and solvent molecules (CHCl₃, CHBr₃, or CH₂Br₂) intercalated between the 2D oxalate network. The magnetic properties and Mössbauer spectroscopy indicate that they undergo long-range ferromagnetic ordering at 5.6 K and a spin crossover of the intercalated [Fe­(sal₂-trien)]⁺ complexes at different temperatures <i>T</i>_1/2. The three compounds present a LIESST effect with a relaxation temperature <i>T</i>_LIESST inversely proportional to <i>T</i>_1/2. The isostructural paramagnetic compound, [Fe^III(sal₂-trien)]­[Zn^IICr^III(ox)₃]·CH₂Cl₂ (<b>2·CH</b>_<b>2</b><b>Cl</b>_<b>2</b>) was also prepared. This compound presents a partial spin crossover of the inserted Fe^III complex as well as a LIESST effect. Finally, spectroscopic characterization of the Fe^III doped compound [Ga_0.99Fe_0.01(sal₂trien)]­[Mn^IICr^III(ox)₃]·CH₂Cl₂ (<b>3·CH</b>_<b>2</b><b>Cl</b>_<b>2</b>) shows a gradual and complete thermal spin crossover and a LIESST effect on the isolated Fe^III complexes. This result confirms that cooperativity is not a necessary condition to observe the LIESST effect in an Fe^III compound