Search results for "magnetic exchange"
showing 10 items of 18 documents
Magneto-structural correlations in a family of ReIVCuII chains based on the hexachlororhenate(IV) metalloligand
2017
Six novel one-dimensional chloro-bridged ReIVCuII complexes of formula {[Cu(L)4][ReCl6]}n, where L = imidazole (Imi, 1), 1-methylimidazole (Meim, 2), 1-vinylimidazole (Vim, 3), 1-butylimidazole (Buim, 4), 1-vinyl-1,2,4-triazole (Vtri, 5) and N,N’-dimethylformamide (DMF, 6) are characterised structurally, magnetically and theoretically. The structures exhibit significant differences in Cu–Cl bond lengths and Re–Cl–Cu bridging angles, resulting in large differences in the nature and magnitude of magnetic exchange interactions between the ReIV and CuII ions. Theoretical calculations reveal the coupling to be primarily ferromagnetic, increasing in magnitude as the bridging angle becomes smaller…
Semiclassical approximation in the magnetic problem of exchange-coupled mixed valence clusters
1994
Abstract The frameworks of the applicability of the semiclassical adiabatic approach suggested by Borras-Almenar, Coronado and Tsukerblat to the magnetic problem of mixed valence clusters are considered in a model taking into account magnetic exchange, double exchange and vibronic interaction. The results for the quantum-mechanical and semicalssical calculation of the temperature-variable magnetic moments are compared with those within the scope of the semiclassical approximation for the dimeric d 1 —d 2 clusters and trimeric d 1 —d 1 —d 2 systems with partial delocalization over a pair of ions. The semiclassical approach describes with high accuracy the temperature dependencies of the magn…
Magnetic exchange interaction in a pair of orbitally degenerate ions: Magnetic anisotropy of [Ti2Cl9]−3
2001
The theory of the kinetic exchange in a pair of orbitally degenerate ions developed by the authors [J. Phys. Chem. A 102, 200 (1998)] is applied to the case of face-shared bioctahedral dimer (overall D3h-symmetry). The effective kinetic exchange Hamiltonian is found for a 2T2–2T2 system taking into account all relevant transfer pathways and charge-transfer crystal field states. The influence of different transfer integrals involved in the kinetic exchange on the energy pattern and magnetic properties of the system is examined. The role of other related interactions (trigonal crystal field, spin–orbit coupling) is also discussed in detail. Using the pseudoangular momentum representation and …
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…
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 …
Interplay of Antiferromagnetic Coupling and Spin Crossover in Dinuclear Iron(II) Complexes
2003
This article reports on the study of the interplay between magnetic coupling and spin transition in 2,2′-bipyrimidine (bpym)-bridged iron(II) dinuclear compounds. Coexistence of both phenomena has been observed in [Fe(bpym)(NCS)2]2bpym, [Fe(bpym)(NCSe)2]2bpym and [Fe(bt)(NCS)2]2bpym (bpym = 2,2′-bipyrimidine, bt = 2,2′-bithiazoline) by the action of external physical factors namely pressure or electromagnetic radiation. Competition between magnetic exchange and spin crossover has been studied in [Fe(bpym)(NCS)2]2bpym at 6.3 kbar. LIESST experiments carried out in [Fe(bpym)(NCSe)2]2bpym and [Fe(bt)(NCS)2]2bpym at 4.2 K have shown that is possible to achieve dinuclear molecules with different…
Experimental and Computational Study of Unique Tetranuclear µ 3 ‐Chloride and µ‐Phenoxo/Chloro‐Bridged Defective Dicubane Cobalt(II) Clusters
2016
Two tetranuclear CoII clusters [Co4(L)2(µ3-Cl)2Cl2] have been prepared by using multidentate diaminobisphenolate ligands. The solid-state structures of the complexes were determined by single-crystal X-ray diffraction. The cores of the cluster compounds can be defined as a two-vertex-deficient dicubane geometry (pseudo-dicubane). In the central unit, the cobalt(II) cations are linked through phenoxide oxygen (outer bridges) and chloride anions (inner bridges), previously unprecedented in this type of cobalt cluster. The magnetic properties were studied by both experimental and computational methods. By using a combination of techniques, we were able to determine the nature and strength of t…
One-dimensional organization of free radicals via halogen bonding
2012
Halogen bonds have been applied for the supramolecular organization of organic free radicals in the solid state and their role in the propagation of the magnetic exchange has been studied.
Synthesis, Structure, and Magnetic Properties of the Oxalate-Based Bimetallic Ferromagnetic Chain {[K(18-crown-6)][Mn(H2O)2Cr(ox)3]}∞ (18-crown-6 = C…
2005
The salt [K(18-crown-6)][Mn(H2O)2Cr(ox)3]·0.5(18-crown-6) (1) has been prepared and structurally and magnetically characterized. It crystallizes in the P21/c space group [a = 21.011(2) A, b = 11.265(2) A, c = 15.748(3) A, β = 105.952(6)°, V = 3584(1) A3, and Z = 4] and contains [Mn(H2O)2Cr(ox)3]∞ chains connected through hydrogen bonding to form 2D anionic networks. The magnetic exchange is ferromagnetic [J = +2.23(2) cm-1] in the chain and also in between chains, reaching bulk ferromagnetic ordering below 3.5 K.
Molecular Magnetic Materials from Polyoxometalates
1994
The significance of polyoxometalates in the field of molecular magnetism is discussed. We show that this kind of inorganic complexes provides remarkable examples for the study of the exchange interactions in clusters. On the other hand, we examine the possibility of using these metal oxide anions as magnetic components of molecular materials containing organic tetrathiafulvalenes as electron donor molecules.