Search results for "osso"
showing 10 items of 801 documents
The Effect of Pressure on the Cooperative Spin Transition in the 2D Coordination Polymer {Fe(phpy) 2 [Ni(CN) 4 ]}
2013
The effect of pressure on the spin-transition properties of the 2D coordination polymer {Fe(phpy)2[Ni(CN)4]} is reported. The study has been carried out by means of variable-temperature (10–310 K) magnetic susceptibility measurements at applied pressures of 105 Pa to 1.0 GPa and spectroscopic studies in the visible region at room temperature (105 Pa–3.0 GPa). As the pressure is increased, the characteristic temperature of the spin transition is displaced to higher temperatures and the thermal hysteresis loop disappears. A cooperative first-order spin transition characterized by a piezo-hysteresis loop about 0.3 GPa wide was observed at 293 K.
A Family of Dinuclear Iron(II) SCO Compounds Based on a 1,3,4‐Thiadiazole Bridging Ligand
2015
A new family of dinuclear iron(II) spin-crossover (SCO) compounds with the formula [Fe2(μ-L)2]X4, with three different counteranions [X = BF4– (1), ClO4– (2) and F3CSO3– (3)], was prepared and characterized by single-crystal X-ray diffraction, variable-temperature magnetic susceptibility and Mossbauer measurements. These are the first dinuclear iron(II) SCO complexes with a 1,3,4-thiadiazole bridging ligand L {with L = 2,5-bis[(2-pyridylmethyl)amino]methyl-1,3,4-thiadiazole}. The magnetic measurements reveal a gradual and incomplete SCO of the three compounds around room temperature, starting from a diamagnetic [LS–LS] state. The diamagnetic ground state is in agreement with the single-crys…
Synthesis of Nanocrystals and Particle Size Effects Studies on the Thermally Induced Spin Transition of the Model Spin Crossover Compound [Fe(phen)2(…
2015
Surfactant-free nanocrystals of the model spin-crossover compound [Fe(phen)2(NCS)2] (phen: 1,10-phenanthroline) have been synthesized applying the reverse micelle technique. The morphology of the nanocrystals, characterized by scanning electronic microscopy, corresponds to rhombohedric platelets with dimensions ranging from 203 × 203 × 106 nm to 142 × 142 × 74 nm. Variation of the concentration of the Fe(BF4)2·6H2O salt in the synthesis has been found to have little influence on the crystallite size. In contrast, the solvent-surfactant ratio (ω) is critical for a good particle growth. The spin transition of the nanocrystals has been characterized by magnetic susceptibility measurements and …
High-temperature spin crossover in a mononuclear six-coordinate cobalt(II) complex.
2014
The six-coordinate cobalt(II) complex of formula [Co(tppz)2](tcm)2 exhibits a thermally induced spin-crossover behavior from a high spin (S = 3/2) at higher temperatures to a low spin (S = 1/2) at lower temperatures, with the low-spin phase being achieved at T ≤ 200 K.
Synthesis, crystal structure, EXAFS, and magnetic properties of catena [mu-tris(1,2-bis(tetrazol-1-yl)propane-N1,N1')iron(II)] bis(perchlorate). Firs…
2000
[Fe(btzp)3](ClO4)2 (btzp = 1,2-bis(tetrazol-1-yl)propane) represents the first structurally characterized Fe(II) linear chain compound exhibiting thermal spin crossover. It shows a very gradual spin transition (T1/2 = 130 K) which has been followed by magnetic susceptibility measurements and 57Fe Mössbauer spectroscopy. The structure has been solved at 200 and 100 K by single-crystal X-ray analysis. It crystallizes in the trigonal space group P3c1 with Z = 2 Fe(II) units at both temperatures. The molecular structure consists of chains running along the c axis in which the Fe(II) ions are linked by three N4,N4' coordinating bis(tetrazole) ligands. The main difference between the two forms ap…
One-dimensional and two-dimensional anilate-based magnets with inserted spin-crossover complexes.
2014
The syntheses, structures, and magnetic properties of a family of bimetallic anilate-based compounds with inserted spin-crossover cationic complexes are reported. The structures of 1-4 present a two-dimensional anionic network formed by Mn(II) and Cr(III) ions linked through anilate ligands with inserted [Fe(III)(sal2-trien)](+) (1), [Fe(III)(4-OH-sal2-trien)](+) (2), [Fe(III)(sal2-epe)](+) (3), or [Fe(III)(5-Cl-sal2-trien)](+) (4) complexes. The structure of 5 is formed by anionic [Mn(II)Cl2Cr(III)(Cl2An)3](3-) chains surrounded by [Fe(II)(tren(imid)3)](2+), Cl(-), and solvent molecules. The magnetic properties indicate that 1-4 undergo a long-range ferrimagnetic ordering at ca. 10 K. On t…
Structural Transformations and Magnetic Effects Induced by Solvent Exchange in the Spin Crossover Complex [Fe(bpp) 2 ][Cr(bpy)(ox) 2 ] 2
2005
Structural, thermal, magnetic and solvent-exchange properties of the spin crossover compound [Fe(bpp)2][Cr(bpy)(ox)2]2 containing paramagnetic anions are given. This complex salt 1 crystallises as a dihydrate with two inequivalent (high-spin and low-spin) FeII sites. The dehydrated compound is a spin-crossover material with T1/2 ↑ = 369 K and T1/2 ↓ = 353 K. Rehydration takes place without loss of crystallinity, yielding a polymorph (2) with 100 % high-spin Fe II sites. The different high-spin fractions in 1 and 2 have been correlated to structural changes in the FeII second coordination sphere. The magnetic response to the presence of different sorbed molecules has also been explored. © Wi…
Structural, Thermal, and Magnetic Study of Solvation Processes in Spin-Crossover [Fe(bpp)2][Cr(L)(ox)2]2·nH2O Complexes
2007
The influence of lattice water in the magnetic properties of spin-crossover [Fe(bpp)2]X2.nH2O salts [bpp = 2,6-bis(pyrazol-3-yl)pyridine] is well-documented. In most cases, it stabilizes the low-spin state compared to the anhydrous compound. In other cases, it is rather the contrary. Unraveling this mystery implies the study of the microscopic changes that accompany the loss of water. This might be difficult from an experimental point of view. Our strategy is to focus on some salts that undergo a nonreversible dehydration-hydration process without loss of crystallinity. By comparison of the structural and magnetic properties of original and rehydrated samples, several rules concerning the r…
Thermal, pressure and light switchable spin-crossover materials
2005
This article reviews the most relevant chemical and structural aspects that influence the spin-crossover phenomenon (SCO). Special attention is focussed on the recent development of SCO coordination polymers. The different approaches currently being explored in order to achieve multifunctionality in SCO materials are discussed.
Spin Crossover – Quo Vadis?
2013
This retrospective essay is an attempt to span the bridge over eight decades of research on spin crossover (SCO), one of the most fascinating dynamic electron structure phenomena of inorganic coordination chemistry. The occurrence of SCO compounds of 3d transition metal ions and their characterization regarding magnetic, optical, vibrational, structural, and thermodynamic properties are briefly addressed. Selected case studies of chemical influences and physical effects (pressure, magnetic field, light) on SCO behavior are discussed. Particular attention is paid to the importance of Mossbauer spectroscopy in SCO studies. Light-induced excited spin state trapping (LIESST) and related photoph…