Going loopy: A new iron(II) spin‐crossover complex displays a 70 K wide thermal hysteresis loop, which can be explained by an intermolecular 2D network of hydrogen bonds. This is the first example of a spin‐crossover complex with wide hysteresis arising from a hydrogen‐bond network; it displays the widest hysteresis to date for a structurally characterized complex.

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The magnetic properties and results from X-ray structure analysis for a new pair of iron(II) spin-crossover complexes [FeL1(meim) 2](meim) ( 1(meim)) and [Fe 2L2(meim) 4](meim) 4 ( 2(meim) 4), with L1 being a tetradentate N 2O 2 (2-) coordinating Schiff-base-like ligand [([3,3']-[1,2-phenylenebis(iminomethylidyne)]bis(2,4-pentane-dionato)(2-)N,N',O (2),O (2)'], L2 being an octadentate, dinucleating N 2O 2 (2-) coordinating Schiff-base-like ligand [3,3',3'',3''']-[1,2,4,5-phenylenetetra(iminomethylidyne)]tetra(2,4-pentanedionato)(2-) N, N', N'', N''', O (2), O (2) ', O (2) '', O (2) '''], and meim being N-methylimidazole, are discussed in this work. Crystalline samples of both complexes show a cooperative spin transition with an approximately 2-K-wide thermal hysteresis loop in the case of 1(meim) ( T 1/2 increase = 179 K and T 1/2 decrease = 177 K) and an approximately 21-K-wide thermal hysteresis loop in the case of dinuclear complex 2(meim) 4 ( T 1/2 increase= 199 K and T 1/2 decrease= 178 K). For a separately prepared powder sample of 2, a gradual spin transition with T 1/2 = 229 K is observed that was additionally followed by Mossbauer spectroscopy. The results from X-ray structure analysis give a deeper insight into the molecule packing in the crystal and, by this, help to explain the increase of cooperative interactions during the spin transition when going from the mononuclear to the dinuclear complex. Both compounds crystallize in the triclinic space group P1, and the X-ray structure was analyzed before and after the spin transition. The change of the spin state at the iron center is accompanied by a change of the O-Fe-O angle, the so-called bite of the equatorial ligand, from about 109 degrees in the high-spin state to 89 degrees in the low-spin state. The cooperative interactions responsible for the thermal hysteresis loop are due to elastic interactions between the complex molecules in both cases. However, due to the higher symmetry of the dinucleating ligand in 2(meim) 4, a 3D network of short contacts is formed, while for mononuclear complex 1(meim), a 2D layer of linked molecules is observed. The spin transition was additionally followed in solution using (1)H NMR spectroscopy for both complexes. In both cases, a gradual spin transition is observed, and the increase of cooperative interactions when going from the mononuclear to the dinuclear system is solely attributed to the extended network of intermolecular contacts.

Lithium silicon phosphorus oxynitride (LiSiPON) thin films with different compositions have been prepared by RF magnetron sputtering in N2 by using three targets xLi2SiO3 · (1 − x) Li3PO4 with x = 0.1, 0.3, and 0.5. Compared with LiPON, the electrical properties of LiSiPON have been improved by introducing silicon. LiSiPON films deposited from the target 0.5Li2SiO3 · 0.5Li3PO4 yield the highest ionic conductivity of up to 9.7 × 10−6 S cm−1 with an activation energy of only 0.41 eV. The main mechanism for increasing ionic conductivity is the enhancement of carrier mobility. By DC polarization measurements the electronic partial conductivity was found at least seven orders of magnitude smaller than the ionic conductivity. Linear voltammetry results showed that the LiSiPON films are electrochemically stable in contact with stainless steel in the voltage range of 0–6 V. The substitution of silicon for phosphorus in the film evidenced from X‐ray photoelectron spectroscopy analysis indicated silicon in the film will create more abundant cross‐linking structures Si–O–P and (P, Si)–N < (P, Si), hence created more Li+ conducting paths which favored the higher mobility of lithium ions and larger ionic conductivity. The optical bandgap was found to decrease with increasing silicon content. We demonstrate that the prepared LiSiPON films with their larger ionic conductivity and low electronic conductivity may serve as an alternative to LiPON for applications in high energy density and high voltage lithium batteries.

Both complexes are spin-crossover compounds that were characterised by using magnetic measurements, X-ray crystallography and temperature-dependent 1 H NMR spectroscopy. Special attention was given to the role of the two

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The reaction of iron(II) acetate with the tetradentate Schiff base like ligands H2L1 ((E,E)‐[{diethyl 2,2′‐[1,2‐phenylenebis‐(iminomethylidyne)]bis[3‐oxobutanato]}]) and H2L2 ([([3,3′]‐[1,2‐phenylenebis(iminomethylidyne)]bis(2,4‐pentane‐dionato)(2‐)‐N,N′,O2,O2′]) in the presence of 1‐meim (1‐methylimidazole) or 2‐meim (2‐methylimidazole) leads to the formation of pentacoordinated or octahedral complexes depending on the used reaction conditions. Two pentacoordinated and four octahedral iron(II) complexes of the composition [FeL1(1‐meim)2] (1), [FeL2(1‐meim)] (2), [FeL2(1‐meim)2] (3), [FeL2(1‐meim)2](DMF) (3(DMF)), [FeL1(2‐meim)](MeOH)0.5 (4) and [FeL1(2‐meim)2] (5) were isolated and structurally characterized. For the 2‐meim complexes a hydrogen bond network between the imidazole N‐H hydrogen and the carbonyl oxygen of the equatorial ligand is formed, while for the 1‐meim derivatives only weak van der Waals interactions are observed. Magnetic measurements were performed on all samples. As expected, the pentacoordinated complexes remain in the high‐spin state in the whole temperature range investigated. For the octahedral complexes, 1 and 5 are pure high‐spin complexes while for 3 and 3(DMF) spin transition behaviour is observed.

Magnetic nanoparticles are critical to a broad range of applications, from medical diagnostics and therapeutics to biotechnological processes and single molecule manipulation. To advance these applications, facile and robust routes to synthesize highly magnetic nanoparticles over a wide size range are needed. Here, we demonstrate that changing the degassing temperature of thermal decomposition of metal acetylacetonate precursors from 90 to 25°C tunes the size of ferrimagnetic Zn x Fe 3-x O 4 nanocubes from 25 to 100 nm, respectively. We show that degassing at 90°C nearly entirely removes acetylacetone ligands from the reaction, which results in an early formation of monomers and a reaction-controlled growth following LaMer's model towards small nanocubes. In contrast, degassing at 25°C only partially dissociates acetylacetone ligands from the metal center and triggers a delayed formation of monomers, which leads to intermediate assembled structures made of tiny irregular crystallites and an eventual formation of large nanocubes via a diffusion-controlled growth mechanism. Using complementary techniques, we determine the substitution fraction x of Zn 2+ to be in the range of 0.35-0.37. Our method reduces the complexity of the thermal decomposition method by narrowing the synthesis parameter space to a single physical parameter and enables fabrication of highly magnetic and uniform zinc ferrite nanocubes over a broad size range. The resulting particles are promising for a range of applications, from magnetic fluid hyperthermia to actuation of macromolecules. File list (2) download file view on ChemRxiv Lak et al. Manuscript.pdf (4.40 MiB) download file view on ChemRxiv Lak et al. Supporting Information.pdf (1.77 MiB)