Search results for "Magnetism"

Thermal-, pressure- and light-induced spin-crossover behviour in the two-dimensional Hofman-like coordination polymer [Fe(3-Clpy)2Pd(CN)4]

2013

The thermal spin-crossover behaviour, photoexcitation and subsequent relaxation, as well as the pressure-induced spincrossover behaviour at 298 K are discussed for the non-porous two-dimensional Hofmann-like coordination polymer [Fe(3-Clpy)(2)Pd(CN)(4)] (1). The title compound undergoes a two-step, cooperative thermal-induced SCO with critical temperatures T-c1(down arrow) = 159.6 K and T-c1(up arrow) = 164.5 K for the first step and T-c2(down arrow) = 141.4 K and T-c2(up arrow) = 148.4 K for the second step. Irradiation of the low-spin state with green light (514 nm) at 10 K induced the photoexcitation of around 60% of the iron(II) centres to the high-spin state (LIESST effect). The subseq…

Coordination polymers based on bridging cyanocarbanions and bis-tridentate p-phenylenediamine ligands

2017

Two new Cu(II) coordination polymeric neutral chains of formula [Cu 2 (1,4-tpbd)(μ-A) 2 (H 2 O) 2 ](A) 2 with A = tcnoet − ( 1 ) and tcnopr − ( 2 ) (1,4-tpbd =  N,N,N′N′ -tetrakis(2-pyridylmethyl)benzene-1,4-diamine, tcnoet −  = 1,1,3,3-tetracyano-2-ethoxypropenide and tcnopr −  = 1,1,3,3-tetracyano-2-propoxypropenide) have been synthesized and characterized by infrared spectroscopy, X-ray diffraction and magnetic measurements. 1  and  2 show alternating chains where the 1,4-tpbd and the cyanocarbanion units (tcnoet − for 1 and tcnopr − for 2 ) alternate as bridging ligands. The molecular structure can be viewed as [Cu 2 (μ-tpbd)] 4+ dinuclear units (with Cu⋯Cu distances of 8.2233(3) for 1 …

A Copper(II)-Cytidine Complex as a Building Unit for the Construction of an Unusual Three-Dimensional Coordination Polymer

2010

The chiral [Cu(cyd) 4 ] 6- anion acts as a multiarmed complex-ligand toward auxiliary copper(II) centers leading to the first example of cytidinate-bridged three-dimensional (3D) coordination polymer of formula [Cu 6 (H 2 O) 7 (ClO 4 ) 3 Cu(cyd) 4 ]-(ClO 4 ) 3 (1). Single crystal X-ray analysis of 1 shows a unique 3D covalent network supported by the exclusive hypercoordination of the cytidinate ligand that bridges four crystallographically independent copper(II) ions via the N3, O2, O2', O3', and O5' set of atoms. Magnetic susceptibility measurements in the temperature range 1.9-295 K reveal the coexistence of ferro- and antiferromagnetic interactions within the hexacopper(II) core of 1, t…

Macrocycle-Based Spin-Crossover Materials

2009

International audience; New iron(II) complexes of formula [Fe(L1)](BF(4))(2) (1) and [Fe(L2)](BF(4))(2) x H(2)O (2) (L1 = 1,7-bis(2'-pyridylmethyl)-1,4,7,10-tetraazacyclododecane; L2 = 1,8-bis(2'-pyridylmethyl)-1,4,8,11-tetraazacyclotetradecane) have been synthesized and characterized by infrared spectroscopy, variable-temperature single-crystal X-ray diffraction, and variable-temperature magnetic susceptibility measurements. The crystal structure determinations of 1 and 2 reveal in both cases discrete iron(II) monomeric structures in which the two functionalized tetraazamacrocycles (L1 and L2) act as hexadentate ligands; the iron(II) ions are coordinated with six nitrogen atoms: four from …

Reliable Propagation of Magnetic Domain Walls in Cross Structures for Advanced Multiturn Sensors

2017

[EN] We develop and analyze an advanced concept for a domain-wall-based sensing of rotations. Moving domain walls in n closed loops with n - 1 intersecting convolutions by rotating fields, we are able to sense n rotations. By combining loops with coprime numbers of rotations, we create a sensor system allowing for the total counting of millions of turns of a rotating applied magnetic field. We analyze the operation of the sensor and identify the intersecting cross structures as the critical component for reliable operation. Specifically, depending on the orientation of the applied field angle with the magnetization in the branches of the cross, a domain wall is found to propagate in an unwa…

Ferromagnetic Coupling in the Bis(μ-end-on-azido)iron(III) Dinuclear Complex Anion of[FeII(bpym)3]2[Fe2III(N3)10]·2H2O

1997

A Combined Experimental and Theoretical Study on the Magnetic Properties of a Family of Bis(μ‐phenoxido)dicopper(II) Complexes Bearing ω‐[Bis(2‐hydro…

2009

Five new neutral bis(μ-phenoxido)dicopper(II) complexes, [Cu2(μ-HL1)2]·3EtOH·H2O (1), [Cu2(μ-HL2)2]·1.65H2O (2), [Cu2(μ-HL3)2(μ-H2O)] (3), [Cu2(μ-HL4)2] (4) and [Cu2(μ-HL5)2(μ-H2O)] (5), were prepared from a family of ω-[bis(2-hydroxy-3,5-dimethylbenzyl)amino]alkan-1-ol ligands (H3L1–H3L5 derived from 2-aminoethanol, 3-aminopropanol, 4-aminobutanol, 5-aminopentanol and 6-aminohexanol, respectively) bearing a [O,N,O,O′] donor set. In complexes 3 and 5, there is also a bridging water molecule between the metallic centres. The copper(II) coordination planes of all these complexes form a roof-like structure (the bridging O atoms are located at the top of the roof). The structural differences fo…

Exchange Coupling in Cyano-Bridged Homodinuclear Cu(II) and Ni(II) Complexes:  Synthesis, Structure, Magnetism, and Density Functional Theoretical St…

2001

The synthesis and structural characterization of several new cyano-bridged copper(II) and nickel(II) homodinuclear complexes is presented. The measure of magnetic properties for these complexes is complemented with a computational study of the exchange coupling for several model structures representing this family of compounds. The influence of several factors on the coupling constant has been examined, coordination position occupied by the bridging ligand, distortions of the coordination environment, and relative disposition of the cyanide ion with respect to the M-M vector. Comparison of experimental and calculated coupling constants allows for the rationalization of the most relevant fea…

Syntheses and Structural Study of Novel Tetranuclear Bis(phenoxido)‐Bridged Cu II Metal–Organic Macrocycles

2012

Six new tetranuclear copper(II) complexes were prepared exploiting novel ditopic alkylenediamine-N,N,N′,N′-tetraphenolate ligands. The geometrical parameters of the compounds can be varied by introducing different solvents of crystallization into the lattice. The structures of all six complexes were determined from single-crystal X-ray diffraction analyses and the magnetic properties of the complexes were estimated by computational DFT calculations. The relationship between the magnetic exchange coupling constant (J) and the Cu–O–Cu angle (θ) in these bis(phenoxido)-bridged complexes was investigated and a magnetostructural correlation was established between J and the θ angle. All studied …

A new tetranuclear defective dicubane azide-bridged cobalt(II) complex

2013

Abstract The new tetranuclear cobalt(II) complex with formula [Co4(N3)8(4,5-diazafluoren-9-one)4] (1) is reported. Complex 1 is a cobalt(II) defective dicubane azide-bridged compound showing only azido bridging ligands in the μ1,1– and μ1,1,1– coordination modes. The magnetic properties of 1 are reported. Magnetic susceptibility measurements indicate ferromagnetic coupling. The magnetic data have been fitted to 2 K by considering two different superexchange coupling constants. The out-of-phase signal χM″ displays frequency-dependence below approximately 9 K.