Search results for "spin crossover"
showing 10 items of 379 documents
Hard-X-ray-induced excited-spin-state trapping.
2007
Inside Back Cover: First Step Towards a Devil's Staircase in Spin-Crossover Materials (Angew. Chem. Int. Ed. 30/2016)
2016
International audience; Periodic and aperiodic spin-state concentration waves form during “Devil's staircase”-type spin-crossover in a new bimetallic 2D coordination polymer {Fe[(Hg(SCN)3)2](4,4′-bipy)2}n. In their Communication on page 8675 ff., J. A. Real, E. Collet et al. describe the appearance of spin-state concentration waves between long-range spatially ordered structures of low- and high-spin states during multistep spin-crossover.
Field-induced slow relaxation of magnetization in a mononuclear Co(II) complex of 2,6-bis(pyrazol-1-yl)pyridine functionalized with a carboxylic acid
2018
Abstract Combining Co(II) with the 2,6-bis-(pyrazol1-yl)pyridine ligand functionalized with a carboxylic acid group (bppCOOH) results in the compound [CoII(bppCOOH)2](ClO4)2·2Me2CO, which shows a field-induced slow relaxation of magnetization as a result of the magnetic anisotropy of the distorted octahedral coordination of high-spin Co(II). Co(II)/Fe(II) solid solutions of bppCOOH have been prepared to study the influence of Co(II) on the spin crossover properties of Fe(II). Magnetic characterization of [Fe0.92Co0.08(bppCOOH)2](ClO4)2 indicates that the Cobalt dopant leads to a reduction of T1/2 and a loss of cooperativity of the spin transition.
Thermal- and light-induced spin crossover in novel 2D Fe(II) metalorganic frameworks {Fe(4-PhPy)(2)[M(II)(CN)(x)](y)}.sH(2)O: spectroscopic, structur…
2009
Five novel two-dimensional coordination polymers {Fe(4PhPy)(2)[M(II)(CN)(4)]}.sH(2)O (4PhyPy = 4-phenylpyridine; 1: M(II) = Pd, s = 0; 2: M(II) = Ni, s = 0; 3: M(II) = Pt, s = 1) and {Fe(4PhPy)(2)[M(I)(CN)(2)](2)}.sH(2)O (4: M(I) = Ag, s = 1; 5: M(I) = Au, s = 0.5) exhibiting spin-crossover properties have been synthesized. They were characterized at various temperatures using X-ray absorption spectroscopy (XAS), powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), and magnetic susceptibility measurements. The occurrence of a cooperative thermal spin transition detected by the magnetic method is located at critical temperatures T(c)( downward arrow)/T(c)( upward arrow) …
Fe(II) spin crossover complexes of a derivative of 2,6-bis(pyrazol-1-yl)pyridine (1-bpp) functionalized with a carboxylic acid in the 3-pyridyl posit…
2019
Abstract The preparation of a new bis(pyrazol-1-yl)pyridine (1-bpp) derivative functionalized with a carboxylic acid in the 3-pyridyl position, bpp3-COOH ligand is reported together with the structure and spin-crossover (SCO) properties of [FeII(bpp3-COOH)2](ClO4)2·0.5EtOH·0.5H2O (1). Magnetic properties of 1 indicate that LS is favored. Desolvation leads to a gradual and incomplete SCO. Solvated and desolvated compounds show LIESST effect.
Heteroleptic Iron(II) Spin-Crossover Complexes Based on a 2,6-Bis(pyrazol-1-yl)pyridine-type Ligand Functionalized with a Carboxylic Acid
2019
Two new heteroleptic complexes [Fe- (1bppCOOH)(3bpp-bph)](ClO4)2·solv (1·solv, solv = various solvents; 1bppCOOH = 2,6-bis(1H-pyrazol-1-yl)- isonicotinic acid; 3bpp-bph = 2,6-bis(5-([1,1′-biphenyl]-4- yl)-1H-pyrazol-3-yl)pyridine) and [Fe(1bppCOOH)- (1bppCOOEt)](ClO4)2 ·0.5Me2CO (2·0.5Me2CO, 1bppCOOEt = ethyl 2,6-bis(1H-pyrazol-1-yl)isonicotinate) were designed and prepared. The heteroleptic compound 1· solv was obtained by the combination of stoichiometric amounts of Fe(ClO4)2, 1bppCOOH, and 3bpp-bph, and it was designed to fine-tune the spin crossover (SCO) properties with respect to the previously reported homoleptic compound [Fe(1bppCOOH)2](ClO4)2. Indeed, the introduction of a new subs…
Spin-crossover compounds based on iron(II) complexes of 2,6-bis(pyrazol-1-yl)pyridine (bpp) functionalized with carboxylic acid and ethyl carboxylic …
2018
International audience; Four new salts of the iron(II) complex of the 2,6-bis(pyrazol-1-yl)pyridine ligand functionalized with a carboxylic acid group (bppCOOH) of formulas [Fe(bppCOOH)2](BF4)2 (1(BF4)2), [Fe(bppCOOH)2](CF3SO3)2·yMe2CO (1(CF3SO3)2·yMe2CO), [Fe(bppCOOH)2](AsF6)2·yMe2CO (1(AsF6)2·yMe2CO) and [Fe(bppCOOH)2](SbF6)2·yMe2CO (1(SbF6)2·yMe2CO) have been prepared and characterized together with a more complete structural and photomagnetic characterization of the previously reported [Fe(bppCOOH)2](ClO4)2 (1(ClO4)2). Furthermore, the iron(II) complex of the ethyl ester derivative of bppCOOH (bppCOOEt) has been prepared and characterized (compound [Fe(bppCOOEt)2](ClO4)2·yMe2CO, 2(ClO4)…
Iron(II) complex of 2-(1H-pyrazol-1-yl)pyridine-4-carboxylic acid (ppCOOH) suitable for surface deposition
2018
The synthesis, structural and magnetic characterization of the tris iron(II) complex of 2-(1H-pyrazol-1-yl)pyridine-4-carboxylic acid (ppCOOH) ligand are reported in [Fe(ppCOOH)3](ClO4)2·0.5H2O·2EtOH. Single crystal structure and magnetic characterization of the bulk compound show that the low-spin state is dominant from 2 to 400 K. ESI-MS and UV–Vis spectroscopy experiments indicate that acetonitrile solutions of this complex are stable with time. ESI-MS confirms the presence of the tris complex in solution. This complex can be deposited onto SiO2 surfaces due to the presence of carboxylic acid groups by immersing the substrates into acetonitrile solutions of the complex. XPS spectra of th…
The First 1,3,4‐Oxadiazole Based Dinuclear Iron(II) Complexes Showing Spin Crossover Behavior with Hysteresis
2015
Three new dinuclear complexes [FeII2(μ-L)2]X4 (L is the bis-tridentate ligand 2,5-bis{[(2-pyridylmethyl)amino]methyl}-1,3,4-oxadiazole and X = ClO4–, BF4– and CF3SO3–) have been synthesized and fully characterized by single-crystal X-ray diffraction, Mossbauer spectroscopy and magnetic susceptibility measurements. Upon cooling, a trapped [high-spin–low-spin] state of the iron(II) centres is detected. Depending on the counterion, a pronounced thermal hysteresis is found. In one case, it was possible to observe a space group change that accompanies the spin transition. This is the first system showing spin crossover based on an oxadiazole ligand.
Strong Cooperative Spin Crossover in 2D and 3D FeII −MI,II HofmannLike Coordination Polymers Based on 2‑Fluoropyrazine
2016
Self-assembling iron(II), 2-fluoropyrazine (Fpz), and [MII(CN)4] 2− (MII = Ni, Pd, Pt) or [AuI (CN)2] − building blocks have afforded a new series of two- (2D) and threedimensional (3D) Hofmann-like spin crossover (SCO) coordination polymers with strong cooperative magnetic, calorimetric, and optical properties. The iron(II) ions, lying on inversion centers, define elongated octahedrons equatorially surrounded by four equivalent centrosymmetric μ4-[MII(CN)4]2− groups. The axial positions are occupied by two terminal Fpz ligands affording significantly corrugated 2D layers {Fe(Fpz)2([MII(CN)4]}. The Pt and Pd derivatives undergo thermal- and light-induced SCO characterized by T1/2 temperatur…