Search results for "spin [structure function]"
showing 10 items of 1132 documents
Remarkable Steric Effects and Influence of Monodentate Axial Ligands L on the Spin-Crossover Properties of trans-[FeII(N4 ligand)L] Complexes
2007
Iron(II) complexes obtained from tetradentate, rigid, linear N4 ligands have been investigated to appraise the influence of steric effects and the impact of trans-coordinated anions on the spin-transition behavior. As expected, the well-designed ligands embrace the metal center, resulting in octahedral iron(II) complexes where the basal plane is fully occupied by the pyridine/pyrazole N4 ligand, while anions or solvent molecules are exclusively axially coordinated. Precursor complexes, namely, [Fe(bpzbpy)(MeOH)2](BF4)2 (where bpzbpy symbolizes the ligand 6,6'-bis(N-pyrazolylmethyl)-2,2'-bipyridine) and [Fe(mbpzbpy)(MeOH)2](BF4)2 (where mbpzbpy symbolizes the ligand 6,6'-bis(3,5-dimethyl-N-p…
Gold(I) Complexes of Ferrocenyl Polyphosphines: Aurophilic Gold Chloride Formation and Phosphine-Concerted Shuttling of a Dinuclear [ClAu···AuCl] Fra…
2016
International audience; A smart steric control of the metallocene backbone in bis- and poly(phosphino)ferrocene ligands favors intramolecular aurophilic interactions between [AuCl] fragments in polynuclear gold(I) complexes. We synthesized and characterized by multinuclear NMR and X-ray diffraction analysis mono-, di-, and polynuclear gold complexes of constrained ferrocenyl diphosphines, which bear either bulky tert-butyl groups or more flexible siloxane substituents at the cyclopentadienyl rings. The complexes meso-1,1'-bis-(diphenylphosphino)-3,3'-di-tert-butylferrocene (4-m), rac-1,1'-bis[bis-(5-methy1-2-furyl)phosphino]-3,3'-di-tert-butyfferrocene (5-r), and rac-1,1'-bis ( diphenylphos…
Tunable Spin-Crossover Behavior of the Hofmann-like Network {Fe(bpac)[Pt(CN) 4 ]} through Host-Guest Chemistry
2013
A study of the spin-crossover (SCO) behavior of the tridimensional porous coordination polymer {Fe(bpac)[Pt(CN)4]} (bpac=bis(4-pyridyl) acetylene) on adsorption of different mono- and polyhalobenzene guest molecules is presented. The resolution of the crystal structure of {Fe(bpac)[Pt(CN) 4]}A?G (G=1,2,4-trichlorobenzene) shows preferential guest sites establishing I?A?A?A?I? stacking interactions with the host framework. These host-guest interactions may explain the relationship between the modification of the SCO behavior and both the chemical nature of the guest molecule (electronic factors) and the number of adsorbed molecules (steric factors). Copyright © 2013 WILEY-VCH Verlag GmbH & …
Dynamic anomaly in the glass transition region of orthoterphenyl
1991
We report on incoherent and coherent neutron scattering results in the supercooled liquid and the glassy regime of the van der Waals fluido-terphenyl using the backscattering and spin echo technique, respectively. A critical comparison of both techniques is presented. The data are analysed in the time domain assuming that microscopic correlation times (τ) scale with the viscosity η according to τ(T)∼η(T)/T. With this assumption we obtain an agreement with several predictions of mode coupling theory: the existence of a critical temperatureT c is shown, independently for both incoherent and coherent data, by a cusp in the temperature dependence of the Debye-Waller factorf Q (T). BelowT c fQ(T…
Ascorbic Acid Oxidation in Sucrose Aqueous Model Systems at Subzero Temperatures
2004
The reduction of Tempol by ascorbic acid in concentrated sucrose solutions was measured by electron paramagnetic resonance (EPR) at temperatures ranging from 16 to −16 °C. This method allowed the determination of the rate constants (k) of this fast reaction, by recording the Tempol reduction as a function of time. The two reactants were initially separated and had to migrate for the reaction to occur. The experimental findings were compared with predicted values according to the equation for diffusion-controlled reaction proposed by Atkins. The experimental reaction rate constants were observed to be lower than the calculated ones. However, the experimental values were found to be controlle…
Triggering the generation of an iron(IV)-oxo compound and its reactivity toward sulfides by RuII photocatalysis
2014
The preparation of [FeIV(O)(MePy2tacn)]2+ (2, MePy2tacn = N-methyl-N,N-bis(2-picolyl)-1,4,7-triazacyclononane) by reaction of [FeII(MePy2tacn)(solvent)]2+ (1) and PhIO in CH3CN and its full characterization are described. This compound can also be prepared photochemically from its iron(II) precursor by irradiation at 447 nm in the presence of catalytic amounts of [Ru II(bpy)3]2+ as photosensitizer and a sacrificial electron acceptor (Na2S2O8). Remarkably, the rate of the reaction of the photochemically prepared compound 2 toward sulfides increases 150-fold under irradiation, and 2 is partially regenerated after the sulfide has been consumed; hence, the process can be repeated several times.…
DNA cleavage reaction induced by dimeric copper(II) complexes of N-substituted thiazole sulfonamides
2005
A new dinuclear copper(II) complex has been synthesised and structurally characterised: [Cu2(tz-ben)4] (Htz-ben = N-thiazol-2-yl-benzenesulfonamide). Its crystal structure, magnetic properties and electronic paramagnetic resonance (EPR) spectra were studied in detail. In the compound the metal centres are bridged by four non-linear triatomic NCN groups. The coordination geometry of the copper ions in the dinuclear entity is distorted square pyramidal (4+1). Two thiazole N and two sulfonamido N atoms occupy the equatorial positions and one sulfonamido O atom is in the axial position. Magnetic susceptibility data show a strong antiferromagnetic coupling, -2J = 114.1 cm(-1). The EPR spectra of…
A novel paramagnetic molecular superconductor formed by bis(ethylenedithio)tetrathiafulvalene, tris(oxalato)ferrate(iii) anions and bromobenzene as g…
2005
The new paramagnetic molecular superconductor ET4[(H3O)Fe(C2O4)3]·C6H5Br (1) (Tc = 4.0 K) contains layers of superconducting ET donors alternating with paramagnetic hexagonal layers formed by (H3O)+, [Fe(C2O4)3]3− and guest C6H5Br molecules located in the hexagonal cavities. Conductivity measurements show metallic behavior from room temperature with a minimum in the resistivity at ca. 50 K followed by a smooth increase and a sharp drop in the resistivity with an onset at 4.0 K and a zero resistance at ca. 1.0 K. Magnetoresistance measurements indicate that Hc1 is about 7 mT and that Hc2 is very anisotropic (Hc2⊥ ≥ 5.5 T and Hc2|| ≈ 0.5 T). Magnetic susceptibility measurements show the expec…
Transport anisotropy and of thin films
2005
Abstract The resistivity R ( T ) of superconducting UNi 2 Al 3 thin films shows a pronounced dependence on the current direction. Specifically, the superconducting transition temperature T c is directional dependent as well as the influence of the magnetic ordering on the transport properties. Also the upper critical field B c 2 ( Θ , T ) is moderately influenced by the probe current direction. These anisotropies are discussed in the framework of multiband superconductivity. The initial slope of the upper critical field B c 2 ′ ( T ) provides evidence for a spin singlet state.
A penetration depth study on the non-centrosymmetric superconductors Li2(Pd1−xPtx)3B
2008
Abstract We study the superconducting order parameter in the non-centrosymmetric compounds Li 2 (Pd 1− x Pt x ) 3 B ( x =0, 0.3, 0.7 and 1) by measuring magnetic penetration depth λ ( T ). The low temperature λ ( T ) shows a linear temperature dependence for x ⩾0.3, but follows exponential-like behavior for lower Pt contents. These findings suggest that a spin-triplet state might gradually develop with increasing x due to the broken inversion symmetry.