			Home About us Contact

Weak Ferromagnetic Coupling (weak + ferromagnetic_coupling)

Distribution by Scientific Domains

Chemistry	100%

Selected Abstracts

A CuIINiII Complex with Ethylenediamine: Crystal Structure and Ferromagnetic Behaviour of an Aqua-Bridged Heterometallic Chain Containing Ambidentate Ni(OAc)42, Blocks

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 22 2010
Oksana V. Nesterova
Abstract A one-pot reaction of copper powder and nickel and ammonium acetates in a CH3OH solution of ethylenediamine (en) yields a unique 1D aqua-bridged polymer [Cu(en)2(,2 -H2O)2Ni(OAc)4]n·4nH2O (1) with an ambidentate Ni(OAc)42, fragment that has not been previously characterized. The basic structural motif of 1 contains a previously unreported heterometallic M(,2 -H2O)M, aqua-bridge chain with alternating metal atoms. A complex system of N/O,H···O hydrogen bonds strengthens the polymeric chains and links them into a supramolecular three-dimensional network. Variable-temperature magnetic susceptibility measurements of 1 revealed a weak ferromagnetic coupling (J = 1.1 cm,1) between the paramagnetic copper(II) and nickel(II) ions, which is transmitted through the oxygen bridges. [source]

One-Dimensional Oxalato-Bridged Metal(II) Complexes with 4 - Amino-1,2,4-triazole as Apical Ligand

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 21 2005
Urko García-Couceiro
Abstract The synthesis, chemical characterization, thermal behavior and magnetic properties of six new one-dimensional oxalato-bridged metal(II) complexes of formula [M(,-ox)(4atr)2]n [MII = Cu (1), Ni (2), Co (3), Zn (4), Fe(5)] and [Cd(,-ox)(4atr)2(H2O)]n (6) (ox = oxalato dianion, 4atr = 4-amino-1,2,4-triazole) are reported. The crystal structures of 1 and 6 have been solved by single-crystal X-ray diffraction, whereas the remaining compounds have been studied by means of X-ray powder diffraction methods. Compounds 1,5 are isomorphous and crystallize in the triclinic space group P1¯ with unit cell parameters for 1 of a = 5.538(1) Å, b = 7.663(1) Å, c = 7.711(2) Å, , = 62.21(1)°, , = 73.91(1)°, , = 86.11(1)°, and Z = 1. The crystal structures are comprised of one-dimensional linear chains in which the trans -[M(4atr)2]2+ units are sequentially bridged by bis(bidentate) oxalato ligands, resulting in an octahedral O4N2 donor set. Cryomagnetic susceptibility measurements show the occurrence of antiferromagnetic intrachain interactions for 2, 3, and 5, whereas compound 1 exhibits a weak ferromagnetic coupling in agreement with the out-of-plane exchange pathway involved. The magnetic behavior of 1 and 2 is analyzed and discussed in the light of the available magneto-structural data for analogous systems. CdII complex crystallizes in the monoclinic space group C2/c with unit cell parameters of a = 16.128(2) Å, b = 6.757(1) Å, c = 11.580(2) Å, , = 104.46(1)°, and Z = 4. Its crystal structure contains one-dimensional chains in which metal centers are heptacoodinated to four oxygen atoms from two symmetry-related bis(bidentate) oxalato bridges, two endocyclic nitrogen atoms of trans -coordinated triazole ligands and one water molecule, to give a CdO4OwN2 pentagonal-bipyramidal geometry. Thermoanalytical and variable-temperature X-ray powder diffraction analyzes show that compound 6 undergoes a reversible dehydration,hydration process in which the anhydrous residue crystallizes with a different crystal lattice retaining the dimensionality of the oxalato,metal framework. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

A Ladder-like One-dimensional Chain Based on a New Biradical and CuII: Crystal Structure and Magnetic Properties,

CHINESE JOURNAL OF CHEMISTRY, Issue 9 2010
Chao Wang
Abstract A new biradical di(4-(1,-oxyl-3,-oxido-4,,4,,5,,5,-tetramethyl-4,,5,-dihydro-1,H -imidazol-2,-yl)phenyl) ether (1) and its copper complex 2 were synthesized and characterized structurally. The X-ray structure determination revealed that, the complex is in the triclinic P -1 space group and displays a ladder-like structure. Each copper atom is surrounded by four oxygen atoms from hexafluoroacetylacetone and two oxygen atoms from biradical. The magnetic measurements show that biradical 1 exhibits a weak intramolecular nitroxide-nitroxide antiferromagnetic coupling and copper complex 2 possesses weak ferromagnetic coupling (J=5.09 cm,1) between CuII and radical, which attributed to interaction between copper spin and the axially coordinated nitronyl nitroxide spin. [source]

A Nonanuclear Copper(II) Polyoxometalate Assembled Around a ,-1,1,1,3,3,3-Azido Ligand and Its Parent Tetranuclear Complex

CHEMISTRY - A EUROPEAN JOURNAL, Issue 6 2005
Pierre Mialane Dr.
Abstract Reaction of CuII, [,-SiW10O36]8,, and N3, affords three azido polyoxotungstate complexes. Two of them have been characterized by single-crystal X-ray diffraction. Complex KNaCs10[{,-SiW10O36Cu2(H2O)(N3)2}2],26,H2O (1) is obtained as crystals in few hours after addition of CsCl. This linear tetranuclear CuII complex consists in two [,-SiW10O36Cu2(H2O)(N3)2]6, units connected through two WO bridges. When the filtrate is left to stand for one night, a new complex is obtained. From both elemental analysis and IR spectroscopy, it has been postulated that this compound could be formulated K1.5Cs5.5[SiW10O37Cu2(H2O)2(N3)],14,H2O (1,a), showing the loss of one azido ligand per polyoxometalate unit. Finally, when no cesium salt is added to the reaction medium, the nonanuclear complex K12Na7[{SiW8O31Cu3(OH)(H2O)2(N3)}3(N3)],24,H2O (2) is obtained after three days. Compound 2 crystallizes in the R3c space group and consists in three {Cu3} units related by a C3 axis passing through the exceptional ,-1,1,1,3,3,3-azido bridging ligand. Each trinuclear CuII unit is embedded in the [,-SiW8O31]10, ligand, an unprecedented tetravacant polyoxometalate, showing that partial decomposition of the [,-SiW10O36]8, precursor occurs with time in such experimental conditions. Magnetically, complex 1 behaves as two isolated {Cu2(,1,1 -N3)2} pairs in which the metal centers are strongly ferromagnetically coupled (J=+224 cm,1, g=2.20), the coupling through the WO bridges being negligible. The magnetic behavior of complex 2 has also been studied. Relatively weak ferromagnetic couplings (J1=+1.0 cm,1, J2= +20.0 cm,1, g=2.17) have been found inside the {Cu3} units, while the intertrimeric magnetic interactions occurring through the hexadentate azido ligand have been found to be antiferromagnetic (J3=,5.4 cm,1) and ferromagnetic (J4=+1.3 cm,1) with respect to the end-to-end and end-on azido-bridged CuII pairs, respectively. [source]