Search results for "spin crossover"

Spin transition in iron complexes induced by heat, pressure, light and nuclear decay

1988

The phenomenon of temperature-dependent spin transition will be introduced and the numerous chemical and physical influences affecting the spin transition characteristics will be discussed. We shall mainly concentrate on the spin crossover system [Fe(2-pic)3]X2·Sol (2-pic=2-aminomethylpyridine; X=Cl, Br; Sol=C2H5OH, CH3OH) and demonstrate how the behaviour of the spin transition5T2g(Oh)⇌1A1g(Oh) is influenced by substituting the metalion, the non-coordinating anions X, the crystal solvent molecules Sol and by isotopic exchange with H/D and14N/15N. It will also be shown that the spin transition is very susceptible to pressure. A quantitative spin state conversion from low spin to high spin c…

Pressure effect on a novel spin transition polymeric chain compound

2000

[Fe(hyptrz)3]A2·H2O (hyptrz = 4-(3′-hydroxypropyl)-1,2,4-triazole and A = 4-chlorobenzenesulfonate) represents a novel iron(II) polymeric chain compound. A discontinuous spin transition has been observed by temperature dependent magnetic susceptibility measurements. The spin transition curves are shifted from 181 K to 324 K as the pressure varies from 1 bar to 5.9 kbar. The shapes of these curves are not strongly modified, and this is interpreted as being due to effective cooperative interactions along the chain. This behaviour under pressure can be extended to the family of iron(II)-1,2,4-triazole polymeric chain spin crossover materials.

Spin Transition Phenomena

2003

Titelbild: One Shot Laser Pulse Induced Reversible Spin Transition in the Spin-Crossover Complex [Fe(C4H4N2){Pt(CN)4}] at Room Temperature (Angew. Ch…

2005

One Shot Laser Pulse Induced Reversible Spin Transition in the Spin-Crossover Complex [Fe(C4H4N2){Pt(CN)4}] at Room Temperature

2005

Solid- and solution-state studies of the novel mu-dicyanamide-bridged dinuclear spin-crossover system {[(Fe(bztpen)]2[mu-N(CN)2]}(PF6)3 x n H2O.

2005

The mononuclear diamagnetic compound {Fe(bztpen)[N(CN)2]} (PF6)CH3OH (1) (bztpen = N-benzyl-N,N′,N′- tris(2-pyridylmethyl)ethylenediamine) has been synthesized and its crystal structure studied. Complex 1 can be considered to be the formal pre-cursor of two new dinuclear, dicyanamide-bridged iron(II) complexes with the generic formula {[(Fe(bztpen)]2[μN(CN)2]}(PF6) 3·nH2O (n = 1 (2) or 0 (3)), which have been characterized in the solid state and in solution. In all three complexes, the iron atoms have a distorted [FeN6] octahedral coordination defined by a bztpen ligand and a terminal (1) or a bridging dicyanamide ligand (2 and 3). In the solid state, 2 and 3 can be considered to be molecu …

Stability and nature of the volume collapse of ε-Fe2O3 under extreme conditions

2018

Iron oxides are among the major constituents of the deep Earth’s interior. Among them, the epsilon phase of Fe2O3 is one of the less studied polymorphs and there is a lack of information about its structural, electronic and magnetic transformations at extreme conditions. Here we report the precise determination of its equation of state and a deep analysis of the evolution of the polyhedral units under compression, thanks to the agreement between our experiments and ab-initio simulations. Our results indicate that this material, with remarkable magnetic properties, is stable at pressures up to 27 GPa. Above 27 GPa, a volume collapse has been observed and ascribed to a change of the local env…

Hysteresis in the spin transition regime of [Fe(NH2trz)3](NO3)2 as probed by ZF-μSR

2006

The thermal spin transition which occurs in the polymeric chain compound [Fe(NH(2)trz)(3)](NO3)(2) above room temperature has been investigated by zero-field muon spin relaxation (mu SR) (similar to 8-402 K). The depolarization curves are best described by a Lorentzian and a Gaussian line that represent fast and slow components respectively. The spin transition is associated with a hysteresis loop of width Delta T = 34 K (T-1/2(up arrow) = 346 K and T-1/2(down arrow) = 312 K) that has been delineated by the temperature variation of the initial asymmetry parameter. Comparison of zero-field and transverse field (20 Oe) mu SR measurements shows that diamagnetic muon species occur over the enti…

Spin Crossover and Paramagnetic Behaviour in Two-Dimensional Iron(II) Coordination Polymers with Stilbazole Push–Pull Ligands

2009

The suitability of the stilbazole push–pull ligands, 4′-dimethylaminostilbazole (DMAS) and 4′-diethylaminostilbazole (DEAS), for the construction of bimetallic FeII–AgI/AuI cyanide-based coordination polymers that exhibit spin crossover properties is investigated. The structural and physical characterization of four novel two-dimensional FeII polymers formulated as {Fe(DMAS)2[Ag(DMAS)(CN)2]2} (1) and {Fe(L)2[M(CN)2]2} (L = DMAS, M = Au (2); DEAS, Ag (3); DEAS, Au (4)) is reported. Polymers 1 and 4 are paramagnetic over the whole range of temperatures studied (5–300 K), whereas 2 and 3 exhibit spin crossover properties.

One-Dimensional Iron(II) Compounds Exhibiting Spin Crossover and Liquid Crystalline Properties in the Room Temperature Region

2008

A novel series of 1D Fe(II) metallomesogens have been synthesized using the ligand 5-bis(alkoxy)- N-(4 H-1,2,4-triazol-4-yl)benzamide (C n -tba) and the Fe(X) 2. sH 2O salts. The polymers obey the general formula [Fe(C n -tba) 3](X) 2. sH 2O [X = CF 3SO 3 (-), BF 4 (-); n = 4, 6, 8, 10, 12]. The derivatives with n = 4, 6 exhibit spin transition behavior like in crystalline compounds, whereas those with n = 8, 10, 12 present a spin transition coexisting with the mesomorphic behavior in the room-temperature region. A columnar mesophase has been found for the majority of the metallomesogens, but also a columnar lamellar mesophase was observed for other derivatives. [Fe(C 12-tba) 3](CF 3SO 3) 2…