Magnetic Properties (magnetic + property)

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Kinds of Magnetic Properties

  • excellent magnetic property

  • Selected Abstracts

    Tetranuclear Manganese Complexes with [MnII4] and [MnII2MnIII2] Units: Syntheses, Structures, Magnetic Properties, and DFT Study,

    Lucjan B. Jerzykiewicz
    Abstract Two tetranuclear manganese compounds, [Mn4(,3,,2 -L)4Br4(LH)4] (1) and [Mn4(,3,,2 -L)2(,,,2 -L)4L2Br2] (2), with cubane and defect dicubane-like cores were synthesized and characterized by single-crystal X-ray diffraction, magnetic measurements, and DFT calculations (LH = 2-methoxyethanol). The magnetic properties of the resulting [Mn4] building blocks are presented and discussed in detail. In particular, in 2 the MnIII,O,MnIII angle 103.12(8) is the largest observed to date for such a system. The conjunction of antiferromagnetic and ferromagnetic interactions within the tetranuclear mixed-valent MnII2MnIII2 complexes results in an unusual ST = 1 ground state. [source]

    A ,3 -Alkoxo-Bridged Tetranuclear [Cu4L2] Copper(II) Complex of a Hexadentate N2O4 Donor Ligand with a [6 + 0] Cu4O4 Cubane Core: Synthesis, Crystal Structure, and Magnetic Properties

    Dipankar Maity
    Abstract A novel hexacoordinating non-Schiff base ligand (H4L) with N2O4 donor atoms has been synthesized by simple Mannich reactions. The use of this ligand with Cu(ClO4)26H2O in different molar ratios as well as pH leads to the formation of a mononuclear species and a tetranuclear CuII complex possessing a cubane [Cu4L2] core with almost equal CuCu separation. In the presence of an excess amount of copper(II) ions and triethylamine at reflux, the mononuclear [CuH2L] species can be converted into the tetranuclear one, whereas the reverse process was not observed even after prolonged reaction time. Both the complexes have been characterized by single-crystal X-ray diffraction and magnetic measurements. Magnetic studies reveal that complex 1 displays a paramagnetic Curie-type behavior whereas 2 displays a singlet-spin ground state induced by strong intramolecular antiferromagnetic interactions. [source]

    Syntheses, Structures and Magnetic Properties of Trinuclear CuIIMIICuII (M = Cu, Ni, Co and Fe) and Tetranuclear [21+12] CuIIMnII,2CuII Complexes Derived from a Compartmental Ligand: The Schiff Base 3-Methoxysalicylaldehyde Diamine Can also Stabilize a Cocrystal

    Arpita Biswas
    Abstract The present investigation describes syntheses, characterization and studies of the mononuclear compound [CuIIL,(H2O)] (1), the triangular, trinuclear monophenoxido-bridged compounds [{CuIIL}2MII(H2O)2](ClO4)2nH2O [2 (M = Cu, n = 0), 3 (M = Ni, n = 3), 4 (M = Co, n = 0), 5 (M = Fe, n = 0)] and the tetrametallic self-assembled complex [{CuIILMnII(H2O)3}{CuIIL}2](ClO4)2H2O (6) derived from compartmental Schiff base ligand, H2L, which is the [2+1] condensation product of 3-methoxysalicylaldehyde and trans -1,2-diaminocyclohexane. Single-crystal X-ray structures of 2, 5 and 6 were determined. Two pairs of terminalcentral metal ions in the trinuclear cores in 2 and 5 are monophenoxido-bridged. Interestingly, the CuO6 and FeO6 environments have tetragonally compressed octahedral geometries. On the other hand, the structure of 6 reveals that it is a [21+12] cocrystal of one diphenoxido-bridged dinuclear [CuIILMnII(H2O)3]2+ dication and two mononuclear [CuIIL] moieties. Cocrystallization in 6 takes place as a result of water encapsulation. The variable-temperature (2,300 K) magnetic susceptibilities of compounds 2,6 have been measured. The exchange integrals obtained are: the CuII3 compound 2, J = ,78.9 cm,1; the CuIINiIICuII compound 3, J = ,22.8 cm,1; the CuIICoIICuII compound 4, J = ,7.8 cm,1; the CuIIFeIICuII compound 5, J = ,3.0 cm,1; the CuII3MnII compound 6, J = ,15.1 cm,1. The monophenoxido-bridging core in 3 and 4 has been proposed after comparison of the structures and magnetic properties of these two compounds with those of 2, 5 and related other compounds. This paper presents rare examples of monophenoxido-bridged CuIIMIICuII (M = Cu, Ni, Co and Fe) compounds, provides an understanding of the structures from magnetic exchange integrals, and, most importantly, reports on the first example of a cocrystal derived from a 3-methoxysalicylaldehyde diamine compartmental ligand. [source]

    Synthesis, Structures, and Magnetic Properties of N -Trialkylsilyl-8-amidoquinoline Complexes of Chromium, Manganese, Iron, and Cobalt as well as of Wheel-Like Hexanuclear Iron(II) and Manganese(II) Bis(8-amidoquinoline)

    Astrid Malassa
    Abstract The transamination of 8-(tert -butyldimethylsilylamino)quinoline with (thf)2Cr[N(SiMe3)2]2 yields monomeric bis[8-(tert -butyldimethylsilylamido)quinoline]chromium(II) (1). Similar reactions of M[N(SiMe3)2]2 (M = Mn, Fe, Co) with 8-(trialkylsilylamino)quinoline lead to the formation of monomeric bis[8-(trialkylsilylamido)quinoline]metal(II) [M = Mn, SiR3 = SiMe2tBu (2a), SiiPr3 (2b); M = Fe, SiR3 = SiMe2tBu (3a),SiiPr3 (3b); M = Co, SiR3 = SiMe2tBu (4a), SiiPr3 (4b)]. The transamination of 8-aminoquinoline with M[N(SiMe3)2]2 (M = Mn, Fe, Co) allows the isolation of the heteroleptic 1:1 and homoleptic 2:1 products. The 1:1 complexes bis[8-amidoquinoline metal(II)bis(trimethylsilyl)amide] [M = Mn (5), Fe (6), Co (7)] are dimeric with bridging 8-amidoquinoline moieties. The 2:1 complexes of Mn and Fe, bis(8-amidoquinoline)manganese(II) (8) and bis(8-amidoquinoline)iron(II) (9), form hexamers with wheel-like molecular structures consisting of metal-centered nitrogen octahedra interconnected by common NN edges. The cobalt complex, bis(8-amidoquinoline)cobalt(II) (10), precipitates as a microcrystalline powder. Investigations of the magnetic properties by DFT corroborate the experimental data for the Mn derivative 8, where an antiferomagnetic coupling is observed. By contrast, calculations on the Fe6 -wheel 9 yield very close-lying ferromagnetically and antiferromagnetically coupled states. [source]

    Assembly of Dinuclear CuII Rigid Blocks by Bridging Azido or Poly(thiocyanato)chromates: Synthesis, Structures and Magnetic Properties of Coordination Polymers and Polynuclear Complexes

    Sergey V. Kolotilov
    Abstract Reaction of a dinuclear cationic copper(II) complex of 4,4,-[2-(3-hydroxyiminobutyl)imino]biphenyl [CuII2(LH)2]2+ with N3, resulted in the formation of a dinuclear azido [CuII2(LH)2(N3)2(H2O)2] complex or a 2D coordination polymer [CuII2(LH)2(N3)2]n. Reaction of the dinuclear complex with [CrIII(NCS)6]3, or [CrIII(NCS)4(NH3)2], produced a 2D polymer {[CuII2(LH)2(CH3CN)2]3[CrIII(NCS)6]2}n or a 1D chain, constructed from tetranuclear units {[CuII2(LH)2][CrIII(NCS)4(NH3)2]2}n. Structures of the compounds were determined by X-ray crystallography and complexes were characterised by the temperature dependency of the magnetic susceptibility and by ESR spectroscopy. Magnetic properties of homometallic compounds were fit with the model of a dimer with the Hamiltonian , = ,J,1,2. For heterometallic complexes ,MT curves were fit as the superposition of magnetism resulting from both [CuII2(LH)2]2+ and the adjacent CrIII -containing anion. J values for the complexes lie in the range from ,12.74(4) to ,17.77(8) cm,1. It was shown that the 4,4,-biphenyl bridge efficiently mediates exchange interactions. [source]

    Bis(terdentate) Pyrazole/Pyridine Ligands: Synthesis, Crystal Structures and Magnetic Properties of Bridged Binuclear and Tetranuclear Copper(II) Complexes

    Akhilesh Kumar Singh
    Abstract A new binucleating bis(terdentate) ligand, 3,5-[3-bis(2-pyridyl)pyrazole-1-ylmethyl]pyrazole (HL2), was synthesized. Reaction of the deprotonated ligand L2 with hydrated CuII salts gives (,-pyrazolato)(,-hydroxido)-bridged binuclear and tetranuclear complexes [L2Cu2(,-OH)(ClO4)(MeCN)](ClO4) (2), [L2Cu2(dmf)2(,3 -OH)]2(ClO4)44dmf (34dmf) and [L2L,Cu2](ClO4)2 [4; HL, = 3-(2-pyridyl)pyrazole]. In these complexes, both ,-OH and ,3 -OH bridges were observed. This contrasts the situation for a dicopper(II) complex of the related bis(terdentate) ligand 3,5-bis[6(2,2,-dipyridyl)]pyrazole (HL1), {L1Cu2(OMe)(MeOH)[,1 - O -(NO3)]}{[Cu2(NO3)2(,-OMe)2]}0.5MeOH (1MeOH), where the shorter and more rigid ligand side arms enforce a larger CuCu separation and the formation of a MeO,HOMe moiety within the bimetallic pocket. Molecular structures of all complexes were elucidated by X-ray crystallography. Variable-temperature magnetic susceptibility measurements (295,2 K) for powdered samples of complexes 2,4 reveal strong antiferromagnetic coupling between two copper centres. The magnitude of the coupling is discussed in view of the structural features. During the preparation of complex 4, partial ligand hydrolysis was also observed, but this strongly depends on the reaction conditions.( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

    Self-Assembly from Discrete Clusters to 2D Network Based on [Fe(phen)(CN)4], and [Fe(bipy)(CN)4],: Synthesis, Structures and Magnetic Properties

    Hua Xiang
    Abstract A series of cyanido-bridged complexes {[FeIII(phen) (CN)4]2[NiL1]}4H2O (1), {[FeIII(bipy)(CN)4]2[NiL1]}4H2O (2), [FeIII(bipy)(CN)4]2[NiL2] (3), {[FeIII(phen)(CN)4]2[CuL3]}5H2O (4), {[FeII(phen)(CN)4][Ni(ea)2]}22H2O (5), {[FeII(phen)(CN)4] [NiL2]2H2O}n (6), {[FeIII(bipy)(CN)4]2[Ni(H2O)2]}6.5H2O}n (7) and {[FeII(bipy)(CN)4][Ni(ea)2]H2O}n (8) were synthesized using H[Fe(phen)(CN)4]2H2O and H[Fe(bipy)(CN)4]2H2O as precursors [L1 = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane, L2 = 3,10-bis(2-phenylethyl)-1,3,5,8, 10,12-hexaazacyclotetradecane, L3 = 3,10-bis(2-hydroxyethyl)-1,3,5,8,10,12-hexaazacyclotetradecane, phen = 1,10-phenanthroline, bipy = 2,2,-bipyridine, ea = ethanolamine). Complexes 1,4 are trinuclear clusters, and 5 is a tetranuclear square. In 6, the [FeII(phen)(CN)4]2, anions alternately bridge the [NiL2]2+ cations to generate a 1D wavy chain. The structure of 7 possesses a 4,2-ribbonlike chain, which contains a NiII2(CN)4FeIII2 square with each NiII atom shared by two adjacent squares. Each FeII and NiII atom in 8 acts as a three-connected node through the cyanido-bridges to generate a 2D network with a 4,82 topological net. Ferromagnetic couplings are found between the low-spin FeIII ions and the NiII ions through the cyanido groups in 1,3 and 7, and a metamagnetic behavior and a frequency dependence of the out-of-phase ac susceptibility are observed in 7. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

    Syntheses, Structures and Magnetic Properties of Dinuclear Copper(II),Lanthanide(III) Complexes Bridged by 2-Hydroxymethyl-1-methylimidazole

    Wei-Xiong Zhang
    Abstract Three discrete dinuclear copper(II),lanthanide(III) complexes, namely, [CuLn(mmi)2(NO3)3(H2O)2] [Ln = La (1), Sm (2)] and [CuGd(mmi)2(NO3)2(H2O)3][NO3] (3) (Hmmi = 2-hydroxymethyl-1-methylimidazole) were synthesized and structurally characterized by X-ray diffraction analysis. In these complexes, dinuclear cores of CuII and LnIII are consolidated by a pair of ,-1,1- O bridges from mmi at a distance of 3.36,3.46 . The temperature dependence of the magnetic susceptibility and the field dependence of the magnetization indicate that 1, 2 and 3 exhibit paramagnetic, antiferromagnetic and ferromagnetic behaviours, respectively. The value of the JCu,Gd coupling constant of 3 [8.7(1) cm,1] is fairly large, which is probably related to the small dihedral angles, , (5.0), between the two planes of O,Cu,O and O,Gd,O in the CuO2Gd core.( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    [(Pyridylcarbonyl)pyridyl]triazolopyridines, Useful Ligands for the Construction of Polynuclear Coordination Compounds , Synthesis, Crystal Structure and Magnetic Properties of a Novel Tetranuclear Copper(II) Cubane,

    Beln Abarca
    Abstract A new tetranuclear cubane Cu4O4 complex has been synthesised from assembly of CuII ions and the polydentate ligand (pyridin-2-yl){6-([1,2,3]triazolo[1,5- a]pyridin-3-yl)pyridin-2-yl}methanone. Crystallographic analysis indicates that the Cu4O4 unit has an S4 symmetry. The magnetic properties have been analysed using the H = ,2,i,jJijSiSj spin Hamiltonian. Two distinct coupling constants, 2J1,3 = ,37.4 cm,1 and 2J1,2 = ,2.6 cm,1, obtained from the fitting of the experimental data have been rationalised on the basis of a density functional study of magnetostructural correlations in cubane complexes containing the Cu4O4 core. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

    Synthesis, Upconversion Luminescence and Magnetic Properties of New Lanthanide,Organic Frameworks with (43)2(46,66,83) Topology

    Danfeng Weng
    Abstract The synthesis and crystal structures of three new lanthanide,organic frameworks [Ln(pza)(OH)(H2O)]n (Ln = Y(1), Er(2), Yb(3); H2pza = 2,3-pyrazinedicarboxylic acid) with helical chains and novel 2D (43)2(46,66,83) topology are reported. The topology is obtained by simplifying the dinuclear metal core as a six-connected node and the ligand as a three-connected linker. The upconversion property measurement gives green and red emissions coming from two-photon excitation of Y: Er, Yb codoped coordination polymer and arising from ErIII transitions of 4S3/2/2H11/2,4I15/2 and 4F9/2,4I15/2. The magnetic properties of complexes 2 and 3 are also studied.( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

    Tetranuclear Nickel Complexes Composed of Pairs of Dinuclear LNi2 Fragments Linked by 4,4,-Bipyrazolyl, 1,4-Bis(4,-pyrazolyl)benzene, and 4,4,-Bipyridazine: Synthesis, Structures, and Magnetic Properties

    Vasile Lozan
    Abstract The ability of the ligands 4,4,-bipyrazolyl (H2bpz), 1,4-bis(4,-pyrazolyl)benzene (H2bpzb), and 4,4,-bipyridazine (bpdz) to link two dioctahedral LNi2 units has been examined. Thefollowing complexes were prepared: [L1NiII2(Hbpz)][BPh4] (6[BPh4]), [L1NiII2(bpdz)][ClO4]2 (7[ClO4]2), [(L1NiII2)2(bpzb)][BPh4]2 (8[BPh4]2), and [(L2NiII2)2(bpz)][BPh4]2 (9[BPh4]2), where (L1)2, and (L2)2, represent macrocyclic hexaaza-dithiophenolate ligands. All complexes have been characterised by UV/Vis spectroscopy, IR spectroscopy, and X-ray crystallography. Whereas (Hbpz), and bpdz in 6[BPh4]2 and 7[ClO4]2 act as bidentate ligands coordinating to only one [LNi2]2+ unit, in 8[BPh4]2 and 9[BPh4]2 the (bpzb)2, and(bpz)2, units are tetradentate linkers. This is qualitatively explained in terms of the absence or presence of steric repulsions between the tBu groups of the supporting ligands and the length of the coligands. The structures of the tetranuclear complexes differ mainly in the distance between the center of the NiNi axes of the isostructural [LNi2] units {14.040(1) in 8[BPh4]2, 9.184(1) in 9[BPh4]2}. The two Ni2pyrazolato planes in 9[BPh4]2 are coplanar. An analysis of the temperature-dependent magnetic susceptibility data for 9[BPh4]2 reveals the presence of weak ferromagnetic exchange interactions between the NiII ions in the binuclear [L2Ni2] subunits with values for the magnetic exchange constant J1 of 23.97 cm,1 (H = ,2JS1S2). The exchange coupling across the dipyrazolato bridge is less than 0.1 cm,1, suggesting that no significant interdimer exchange coupling occurs in 9[BPh4]2. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

    Transition-Metal (MnII and CoII) Complexes with the Heteropolymolybdate Fragment [AsVMo9O33]7,: Crystal Structures, Electrochemical and Magnetic Properties

    Yanyan Yang
    Abstract Two novel heteropolymolybdates, [(CH3)4N]8n[M(H2O)5]2n(H3O)2n[{M(H2O)5}2(MAsVMo9O33)2]n[M(H2O)4(MAsVMo9O33)2]n20nH2O (M = Mn2+, 1; M = Co2+, 2), constructed from the new fragment (AsVMo9O33)7, and a transition metal have been synthesized in aqueous solution and characterized by elemental analysis, IR spectroscopy, thermal gravimetric analysis, and single-crystal X-ray diffraction. Structurally the title complexes resemble a sandwich-type complex because they involve the coordination of two transition metals to two [AsVMo9O33]7, fragments, which derive from the well-known B -, - Keggin structure. Compounds 1 and 2 exhibit a one-dimensional chain-like framework [M(H2O)4(MAsVMo9O33)2]8n, with isolated {[M(H2O)5]2(MAsVMo9O33)2}6, units residing among the chains. The magnetic properties of the two complexes were investigated to indicate typical antiferromagnetic interactions through the MnII,O,MnII bridge unit for complex 1 and the CoII,O,CoII bridge unit for complex 2. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

    Synthesis, Crystal Structure, and Magnetic Properties of Two Manganese(II) Polymers Bearing Ferrocenecarboxylato Ligands

    Zilu Chen
    Abstract Reactions of Mn(ClO4)26H2O with FcCO2Na [Fc = (,5 -C5H4)Fe(,5 -C5H5)] in methanol solution gave [Mn3(FcCO2)6(CH3OH)4]n (1), and, in the presence of 4,4,-bipyridine (4,4,-bpy), [Mn3(FcCO2)6(H2O)2(4,4,-bpy)]n (2). Both complexes have the similar chains with a sequence of ,Mn,(,2 -COO)n,Mn,(,2 -COO),Mn,(,2 -COO),Mn,(,2 -COO)n,Mn, (n = 4 and 2 for complex 1 and 2, respectively), which are constructed alternatively from mononuclear [MnII] units and dinuclear [Mn2(FcCO2)4] units by ,2 -ferrocenecarboxylato- O,O, bridging. The two MnII ions in the dinuclear [Mn2(FcCO2)4] units of complex 1 are connected by four ferrocenecarboxylato ligands to form a swastika-like shaped skeleton, which is rare in metallocenecarboxylato complexes. However, the two MnII ions in the dinuclear [Mn2(FcCO2)4] units of complex 2 are bridged only by two carboxylato ligands, and the other two ferrocenecarboxylato ligands in this unit bind in a chelating mode. The chains in complex 2 are further interconnected by the coordinated 4,4,-bipyridine molecules to form two-dimensional coordination sheets. Magnetic susceptibility measurements revealed a weak antiferromagnetic coupling for both complexes. A model Heisenberg chain comprising classical spins coupled through alternating exchange interactions J1,J1,J2 (AF1,AF1,AF2) is proposed to describe the magnetic behavior. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

    Synthesis, Structure and Magnetic Properties of a Tetranuclear Copper(II) Complex on the Basis of a 2-Substituted Glucopyranoside Schiff Base Ligand,

    Anja Burkhardt
    Abstract Condensation of a derivatized 2-aminoglucose fragment with salicylaldehyde affords the new sugar-based Schiff base ligand benzyl 4,6- O -benzylidene-2-deoxy-2-salicylideneamino-,- D -glucopyranoside (H2L). The reaction of the dibasic ligand H2L with [Cu(CH3COO)2]H2O leads to the formation of the tetranuclear copper(II) complex [{Cu(L)}4] (3) by a self-assembly process. The X-ray structural analysis of complex 3 which crystallizes together with two molecules of chloroform and one molecule of ethanol in the space group P212121 revealed for all copper atoms a NO3 coordination environment with a square-planar geometry. The tetranuclear molecule 3 consists of four chiral building blocks {Cu(L)} with the rare 2,3-coordination of the trans -configured donor atoms of the sugar backbone. The observed coordination mode of the building blocks exemplifies how chitosan-derived polysaccharide ligands can act as a chiral support for transition-metal complexes. The C-3 alcoholate oxygen atoms of the carbohydrate unit is bridging adjacent {Cu(L)} moieties resulting in an eight-membered Cu4O4 ring with a boat-like conformation. Temperature-dependent magnetic measurements of 3 indicate moderate antiferromagnetic interactions between the four copper(II) ions with a coupling constant of J = ,130 cm,1.( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

    A Ferromagnetically Coupled, Bent, Trinuclear Copper(II) Complex: Synthesis, Structure, Hydrogen-Bonding Network, Magnetic Properties and DNA Interaction Study

    Sumana Sarkar
    Abstract A bent trinuclear copper(II) complex (1) incorporating ,-phenoxo, ,- syn - syn carboxylato, and ,3 -chloro bridges and an O,N,N -coordinated reduced Schiff-base ligand is reported. The complex shows an intramolecular ferromagnetic interaction in the solid state. The EPR spectra also support the magnetic behaviour of the complex. In the compound, each copper centre has a square-pyramidal geometry. The separation between the adjacent copper ions is about 3.05 and that between the terminal copper ions is about 5.0 . The complex forms a supramolecular architecture through N,HCl hydrogen bonding between the amine group of the reduced Schiff-base ligand and the counter chloride anions. Absorption and fluorescence spectral studies and viscosity measurements have been performed to determine the type of interaction with calf-thymus DNA. The nuclease activity of the complex with plasmid DNA is also studied. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

    Syntheses, Crystal Structures and Magnetic Properties of Carboxylato-Bridged Polymeric Networks of MnII

    Subal Chandra Manna
    Abstract Three new carboxylato-bridged polymeric networks of MnII having,molecular formula [Mn(ox)(dpyo)]n (1), {[Mn2(mal)2(bpee)(H2O)2]0.5(bpee)0.5(CH3OH)}n (2) and {[Mn3(btc)2(2,2,-bipy)2(H2O)6]4H2O}n (3) [dpyo, 4,4,-bipyridine N,N,-dioxide; bpee, trans -1,2 bis(4-pyridyl)ethylene; 2,2,-bipy, 2,2,-bipyridine; ox = oxalate dianion; mal = malonate dianion; btc = 1,3,5-benzenetricarboxylate trianion] have been synthesized and characterized by single-crystal X-ray diffraction studies and low temperature magnetic measurements. Structure determination of complex 1 reveals a covalent bonded 2D network containing bischelating oxalate and bridging dpyo; complex 2 is a covalent bonded 3D polymeric architecture, formed by bridging malonate and bpee ligands, resulting in an open framework with channels filled by uncoordinated disordered bpee and methanol molecules. Whereas complex 3, comprising btc anions bound to three metal centers, is a 1D chain which further extends its dimensionality to 3D via - and H-bonding interactions. Low temperature magnetic measurements reveal the existence of weak antiferromagnetic interaction in all these complexes. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

    Synthesis, Structure and Magnetic Properties of a Novel Linear CuII -Trimer Complex

    Vladimir Pashchenko
    Abstract A new hexanuclear copper(II) sandwich complex based on two 10-membered macrocyclic phenylsiloxanolate ligands, {Cu6[(C6H5SiO2)5]2(OH)2(C10H8N2)2}4(DMF)3(H2O) (1), was synthesized and characterized by single-crystal X-ray diffraction and measurements of the magnetic susceptibility and isothermal magnetization. The cluster compound crystallizes in the triclinic system, space group P (No. 2), with a = 14.925(3) , b = 16.745(2) , c = 23.053(3) , , = 83.079(9), , = 84.836(13), , = 65.019(17), and Z = 2. The unit cell contains two identical molecules, each consisting of six interacting Cu2+ (S = 1/2) ions. Within the molecule, the six Cu2+ ions are arranged in two almost linear, parallel trimers. While pairs of oxygen atoms link the Cu2+ ions within the trimers, single oxygen atoms residing at the ends of the trimers provide the strongest intertrimer bonds. Magnetic measurements reveal an antiferromagnetic intratrimer exchange interaction, J/kB = 85 K, as the dominant magnetic coupling of the complex. By introducing a weak antiferromagnetic intertrimer coupling, J,/kB = 3.5 K, a satisfactory description of the magnetic behavior over a wide range of temperature and magnetic field is obtained. The departure of the model curves from the data at the lowest available temperature indicates the presence of additional, weak intra - and/or intermolecular interactions. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

    Coordination Chemistry of N,N,N,,N, -Tetraethylpyridine-2,6-dithiocarboxamide (S -dept) , X-ray Crystal Structures and Magnetic Properties of [Co(S -dept)X2] (X = Br, I, and NCS)

    Ramesh Kapoor
    Abstract Mononuclear cobalt(II) complexes [Co(S -dept)X2] [X = Br (1), I (2) and NCS (3)] were synthesized using N,N,N,,N, -tetraethylpyridine-2,6-dithiocarboxamide (S -dept), and characterised by conductivity, spectral and single-crystal X-ray diffraction studies. These studies reveal that the compounds consist of discrete monomeric molecules in which the cobalt atoms are five-coordinate in an environment that is best described as being distorted square-pyramidal. In dimethylformamide the iodo complex shows significant ionic dissociation (1:1 electrolyte) and its crystal field absorption spectrum is interpretable in terms of an octahedral structure [Co(S -dept)(DMF)2I]+. The temperature dependence of the magnetic susceptibility data is indicative of a high-spin compound with an important zero-field splitting. The best fitwas obtained with |D| = 20.5 cm,1 and g = 2.53 for 1, |D| = 14.2 cm,1 and g = 2.38 for 2 and |D| = 17.7 cm,1 and g = 2.35 for 3. The X-band EPR spectra at low temperature is also characteristic of an S = 3/2 state with important zero-field splitting. The most important band appears at low fields (ca. 1200 G). ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

    A New Spherical Metallacryptate Compound [Na{Cu6(Thr)8(H2O)2(ClO4)4}]ClO45,H2O: Magnetic Properties and DFT Calculations

    Sheng-Chang Xiang
    Abstract The hexanuclear copper(II) complex with threoninato acid has been synthesized. Its structure can be described as an octahedron cage with D2h symmetry in which six copper ions are bound by eight threoninato acids with a [3.11223130] coordination mode and one Na+ cation being captured within the center of the cage. In contrast with other hexanuclear copper compounds containing amino acids, the title compound has a prolate Cu6 octahedron with the longest axial distance and a rectangle equatorial plane, as well as special coordinated perchlorate ions. Compared with classic cryptate, hexanuclear copper(II) compounds with amino acids can be regarded as a new topologic type of spherical macrotricyclic metallacryptates [2,2,2,2] whose cages have a high selectivity for sodium ions. The analysis of magnetic susceptibility data shows that the threoninato compound has a ground state with spin S = 3. The computing coupling constant between the equatorial Cu centers and the axial ones is 4.4 cm,1,calculated by using DFT methods for a model compound. This is close to three known experimental values of 1.39, 0.56 or 0.43 cm,1 for complexes with 4-hydroxy- L -prolinato, L -prolinato or L -threoninato acid as ligands, respectively. The dominant ferromagnetic interactions for these complexes can be essentially attributed to the orthogonality between the magnetic orbitals, dxz or dyz orbitals for the equatorial CuII centers and d orbitals for the axial ones. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

    Dinuclear Complexes of MII Thiocyanate (M = Ni and Cu) Containing a Tridentate Schiff-Base Ligand: Synthesis, Structural Diversity and Magnetic Properties

    Suparna Banerjee
    Abstract A dinuclear NiII complex, [Ni2(L)2(H2O)(NCS)2]3H2O (1) in which the metal atoms are bridged by one water molecule and two ,2 -phenolate ions, and a thiocyanato-bridged dimeric CuII complex, [Cu(L)NCS]2 (2) [L = tridentate Schiff-base ligand, N -(3-aminopropyl)salicylaldimine, derived from 1:1 condensation of salicylaldehyde and 1,3-diaminopropane], have been synthesized and characterized by IR and UV/Vis spectroscopy, cyclic voltammetry and single-crystal X-ray diffraction studies. The structure of 1 consists of dinuclear units with crystallographic C2 symmetry in which each NiII atom is in a distorted octahedral environment. The Ni,O distance and the Ni,O,Ni angle, through the bridged water molecule, are 2.240(11) and 82.5(5), respectively. The structure of 2 consists of dinuclear units bridged asymmetrically by di-,1,3 -NCS ions; each CuII ion is in a square-pyramidal environment with , = 0.25. Variable-temperature magnetic susceptibility studies indicate the presence of dominant ferromagnetic exchange coupling in complex 1 with J = 3.1 cm,1, whereas complex 2 exhibits weak antiferromagnetic coupling between the CuII centers with J = ,1.7 cm,1. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

    Hydrothermal Synthesis, Structure and Magnetic Properties of a One-Dimensional Iron Arsenate, 1,[NH3(CH2)2NH(CH2)2NH3][Fe2F4(HAsO4)2]

    Sandip Chakrabarti
    Abstract A novel one-dimensional iron arsenate, 1,[NH3(CH2)2NH(CH2)2NH3][Fe2F4(HAsO4)2], built up exclusively from SBU-4 units (two octahedral units sharing an edge and connected through two tetrahedra) with Fe3+ ions in the high-spin state has been synthesized by hydrothermal methods. Structure elucidation reveals that the compound is a two-leg ladder with very weak antiferromagnetic exchanges along the chains. The magnetic susceptibility data show activated behaviour at T = 14 K, suggesting a finite spin gap between the nonmagnetic ground state and the excited triplet state. We have estimated the exchange parameters theoretically based on the S = 5/2 Majumdar,Ghosh model with frustrations and dimerisations. Although the magnetic gap is quite small, this is the first example, to the best of our knowledge, where the rungs with two S = 5/2 spins form strong singlet dimers. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

    Synthesis, Crystal Structure, and Magnetic Properties of Mn2(OH)2SO4: A Novel Layered Hydroxide

    Mohsen Ben Salah
    Abstract Mn2(OH)2SO4, obtained as pink prismatic crystals by the hydrothermal reaction of MnSO4H2O and NaOH at 240 C for 24 h, consists of layers of Mn hydroxide connected to each other through 6 -sulfate ions. Each layer exhibits vacancies, and each vacant space is capped at the top and bottom by the sulfate groups. The compound is paramagnetic above 50 K (C = 4.36 emu K mol,1, eff = 5.91 B, , = ,100 K). Below 45 K, the magnetization increases slightly, indicating canted-antiferromagnetic (TNel = 421 K) behavior consistent with the linear dependence of the magnetization as a function of the field at 2 K, which reaches only 0.4 B at 50 kOe, and the lack of any imaginary component of the ac-susceptibilities (ac = alternating current). ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

    Syntheses, Structures, and Magnetic Properties of Copper(II) Complexes with 1,3-[Bis(2-pyridylmethyl)amino]benzene (1,3-tpbd) as Ligand

    Simon P. Foxon
    Abstract The dinuclear copper(II) complexes {[Cu2(1,3-tpbd)(H2O)(OAc)2](ClO4)2}0.23{[Cu2(1,3-tpbd)(H2O)2(OAc)](ClO4)3}0.770.77H2O (1), [Cu2(1,3-tpbd)(H2O)2(OAc)2](ClO4)22H2O (2), and the tetranuclear copper(II) complex [Cu4(1,3-tpbd)2(H2O)2(SO4)4]8H2O (3) {1,3-tpbd = 1,3-bis[bis(2-pyridylmethyl)amino]benzene} were synthesised and structurally characterised by X-ray diffraction. Variable-temperature (2.0,290 K) magnetic susceptibility measurements on these complexes as well as on the dinuclear copper(II) complex [Cu2(1,3-tpbd)(H2O)2(ClO4)3]ClO4 (4) (whose structure was published earlier) were performed. In contrast to 2 and 3, significant ferromagnetic coupling with J = +9.3 cm,1 was observed for 4 (the Hamiltonian being defined as H, = ,J S,1S,2). Density functional theory (DFT) calculations were used successfully for the interpretation of the ferromagnetic coupling observed in 4. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

    Tuning the Magnetic Properties of a Dinuclear Copper Complex: From Ferromagnetic to Antiferromagnetic Coupling

    Simon P. Foxon
    Abstract A novel structural motif in oxalate bridged copper(II) complexes has been prepared namely a metallamacrocyclic compound of the dinucleating ligand 1,3-bis[bis(2-pyridylmethyl)amino]benzene (= 1,3-tpbd). It could be demonstrated that the magnetic properties of copper(II) complexes of the 1,3-tpbd ligand can be adjusted from weakly ferromagnetic (J = +9.3 cm,1) to strongly antiferromagnetic [J = ,366(9) cm,1] by variation of the additional ligands (e.g. perchlorate, azide, oxalate etc.). ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

    Bent and Linear Forms of the (,-Oxo)bis[trichloroferrate(III)] Dianion: An Intermolecular Effect , Structural, Electronic and Magnetic Properties

    Agust Lleds
    Abstract We have analyzed the great diversity of Fe,O,Fe angles, 140,180, found in the X-ray structures of the (,-oxo)bis[trichloroferrate(III)] dianion [Cl3FeOFeCl3]2, from both experimental and theoretical points of view. Theoretical calculations show that only the linear isomer is found as a minimum on the potential energy surface. Detailed analysis of the crystal packing indicates that the angular form is due to attractive intermolecular interactions. Analysis of a selected reduced set of the 45 crystal structures retrieved from the Cambridge Structural Database allowed us to classify the bending of the [Cl3FeOFeCl3]2, dianion in three categories, depending on the balance and strength of the intermolecular OH,X contacts. A crystal diffraction study on the bis(benzyltrimethylammonium) salt has shown both bent (144.6) and linear (180) forms of the (,-oxo)bis[trichloroferrate(III)] dianion. The magnetic susceptibility of this compound has been fitted by assuming two equally weighted contributions (Jang and Jlin) of the two forms, considering Jang , Jlin estimated by theoretical calculations. The obtained Jang and Jlin of ,117 and ,133 cm,1 respectively, agree well with B3LYP results. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

    Exchange Interactions at the Supramolecular Level , Synthesis, Crystal Structure, Magnetic Properties, and EPR Spectra of [Mn(MAC)(TCNQ)2] (MAC = Pentaaza Macrocyclic Ligand; TCNQ, = Radical Anion of 7,7,8,8-Tetracyano- p -quinodimethane)

    Augustin M. Madalan
    Abstract The reaction between [Mn(MAC)(H2O)2]Cl24H2O and LiTCNQ (MAC = 2,13-dimethyl-3,6,9,12,18-pentaazabicyclo[12.3.1]octadeca-1(18),2,12,14,16-pentaene) affords a complex with the formula [Mn(MAC)(TCNQ)2] (1), whose crystal structure has been determined. Its structure consists of neutral mononuclear entities. The manganese(II) ion is heptacoordinated, with a pentagonal bipyramidal geometry. The apical positions are occupied by the TCNQ, radicals, while the macrocyclic ligand is coordinated at the equatorial positions. The seven Mn,N distances range from 2.273(3) to 2.301(6) . The strong intermolecular ,,, stacking interactions between the TCNQ radicals (3.2 ) leads to weave-like infinite chains, which propagate along the crystallographic c axis. The cryomagnetic investigation of 1 revealed a weak intermolecular antiferromagnetic coupling of the Mn2+ ions (J = ,0.18 cm,1), which is mediated by the diamagnetic (TCNQ)22, pairs resulting from the stacking interactions in the crystal. The intermolecular exchange interaction between the Mn2+ ions was further confirmed by variable temperature EPR spectroscopic measurements [|J| = 0.15(5) cm,1], which have been carried out in both the X and Q bands. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

    Optimization of the Magnetic Properties of FePd Alloys by Severe Plastic Deformation,

    Abdelahad Chbihi
    Abstract A FePd alloy was nanostructured by severe plastic deformation following two different routes: ordered and disordered states were processed by high pressure torsion (HPT). A grain size in a range of 50 to 150,nm is obtained in both cases. Severe plastic deformation induces some significant disordering of the long range ordered L10 phase. However, transmission electron microscopy (TEM) data clearly show that few ordered nanocrystals remain in the deformed state. The deformed materials were annealed to achieve nanostructured long range ordered alloys. The transformation proceeds via a first order transition characterized by the nucleation of numerous ordered domains along grain boundaries. The influence of the annealing conditions (temperature and time) on the coercivity was studied for both routes. It is demonstrated that starting with the disorder state prior to HPT and annealing at low temperature (400,C) leads to the highest coercivity (about 1.8,kOe). [source]

    High-Pressure Torsion for Giant Magnetoresistance and Better Magnetic Properties,

    Shingo Nishihata
    High-pressure torsion (HPT) was conducted on Cu alloys containing ferromagnetic Co and Fe particles. Electron probe microanalysis, X-ray diffraction analysis, and transmission electron microscopy confirmed that the particles were significantly refined through fragmentation and some fractions were dissolved into the Cu matrix with straining by HPT. Saturation magnetization decreases with straining and coercive force increases with straining but they level off after intense straining. Magnetoresistance with an isotropic feature corresponding to giant magnetoresistance (GMR) appears at room temperature by processing with HPT. It is demonstrated that HPT is a potential process for controlling magnetic properties such as saturation magnetization and coercive force and also for creating GMR in the alloys prepared by conventional ingot metallurgy. [source]

    Dynamic Magnetic Properties of Ferroic Films, Multilayers, and Patterned Elements

    Robert L. Stamps
    Abstract Modification and control of material properties through careful manipulation of geometry on nano- and sub-nanometer length scales is a cornerstone of modern materials science and technology. An exciting area in which these concepts have provided exceptional advances has been magnetoelectronics and nanomagnetism. Important scales in magnetic metals are conduction spin diffusion lengths and distances over which local moments correlate. Advanced techniques now allow for the creation of structures patterned on these length scales in three dimensions. The focus of this article is on magnetic structures whose dynamic properties can be strongly modified by ion bombardment and lithographic patterning. Examples are given of how microwave frequency properties can be tuned with external fields, how factors controlling magnetic switching can be controlled, and how manipulation of magnetic domain walls can be used to reveal new and surprising phenomena. [source]

    Giant Electric Field Tuning of Magnetic Properties in Multiferroic Ferrite/Ferroelectric Heterostructures

    Ming Liu
    Abstract Multiferroic heterostructures of Fe3O4/PZT (lead zirconium titanate), Fe3O4/PMN-PT (lead magnesium niobate-lead titanate) and Fe3O4/PZN-PT (lead zinc niobate-lead titanate) are prepared by spin-spray depositing Fe3O4 ferrite film on ferroelectric PZT, PMN-PT and PZN-PT substrates at a low temperature of 90,C. Strong magnetoelectric coupling (ME) and giant microwave tunability are demonstrated by a electrostatic field induced magnetic anisotropic field change in these heterostructures. A high electrostatically tunable ferromagnetic resonance (FMR) field shift up to 600,Oe, corresponding to a large microwave ME coefficient of 67,Oe cm kV,1, is observed in Fe3O4/PMN-PT heterostructures. A record-high electrostatically tunable FMR field range of 860 Oe with a linewidth of 330,380,Oe is demonstrated in Fe3O4/PZN-PT heterostructure, corresponding to a ME coefficient of 108,Oe cm kV,1. Static ME interaction is also investigated and a maximum electric field induced squareness ratio change of 40% is observed in Fe3O4/PZN-PT. In addition, a new concept that the external magnetic orientation and the electric field cooperate to determine microwave magnetic tunability is brought forth to significantly enhance the microwave tunable range up to 1000,Oe. These low temperature synthesized multiferroic heterostructures exhibiting giant electrostatically induced tunable magnetic resonance field at microwave frequencies provide great opportunities for electrostatically tunable microwave multiferroic devices. [source]