Search results for "antiferromagnetism"
showing 10 items of 471 documents
Synthesis, crystal structure and magnetic properties of [Cu2(bpym)(N3)4] (bpym=2,2′-bipyrimidine)
1993
Abstract The compound of formula [Cu 2 (bpym)(N 3 ) 4 ] (bpym=2,2′-bipyrimidine) has been synthesized and its crystal structure determined by X-ray diffraction methods. It crystallizes in the monoclinic space group P 2 1 / n with cell constants: a =10.071(2), b =6.376(1), c =11.617(2) A and β=95.93(1)°; V =742.0(2) A 3 , D (calc., Z =2)=2.029 g cm −3 , M r =453.4, F (000)=448, λ (Mo Kα)=0.71073 A, μ (Mo Kα)=29.1 cm −1 and T =298 K. A total of 2027 reflections was collected over the range 3⩽2θ⩽55°; of these, 1723 were unique and 1427 were considered as observed ( I >3σ( I )) and used in the structural analysis. The final R and R w residuals were 0.0275 and 0.0328, respectively. The structure…
Iron(III), chromium(III) and cobalt(II) complexes with squarate: Synthesis, crystal structure and magnetic properties
2011
The preparation and variable temperature-magnetic investigation of three squarate-containing complexes of formula [Fe 2 (OH) 2 (C 4 O 4 ) 2 (H 2 O) 4 ]·2H 2 O ( 1 ) [Cr 2 (OH) 2 (C 4 O 4 ) 2 (H 2 O) 4 ]·2H 2 O ( 2 ) and [Co(C 4 O 4 )(H 2 O) 4 ] n ( 3 ) [H 2 C 4 O 4 = 3.4-dihydroxycyclobutene-1,2-dione (squaric acid)] together with the crystal structures of 1 and 3 are reported. Complex 1 contains discrete centrosymmetric [Fe 2 (OH) 2 (C 4 O 4 ) 2 (H 2 O) 4 ] diiron(II) units where the iron pairs are joined by a di-μ-hydroxo bridge and two squarate ligands acting as bridging groups through adjacent oxygen atoms. Two coordinated water molecules in cis position complete the octahedral environ…
A Comparative Structural and Magnetic Study of Three Compounds Based on the Cluster Unit M4Cl8(THF)6 (M=Mn, Fe, Co)
2001
Treatment of anhydrous M Cl 2 phases with THF under refluxing conditions leads to excision of the clusters M 4 Cl 8 (THF) 6 ( M =Fe (1), Co (3)) and dimensional reduction to the chain of clusters, {Mn 4 Cl 8 (THF) 6 (Mn(THF) 2 Cl 2 } ∞ , (2). All three compounds were isolated in high yields as crystalline materials and subjected to comprehensive magnetic studies. X-ray structures of the three compounds were performed to verify the nature of the compounds, but only the Mn derivative is discussed in detail due to the fact that the structures of the Fe and Co clusters were reported earlier. The molecular structures of M 4 Cl 8 (THF) 6 ( M =Fe, Co) consist of a rhombic arrrangement of metal ion…
Synthesis, crystal structure and magnetic properties of two alternating double μ1,1 and μ1,3 azido bridged Cu(ii) and Ni(ii) chains
2014
Two new alternating μ1,1- and μ1,3-azido bridged chains, [Cu(N3)2(mtn)]n (1) and [Ni(N3)2(mtn)]n (2) where mtn = N-methyl-1,3-propanediamine, have been synthesized and characterized by single crystal X-ray diffraction. In both complexes, each metal atom is coordinated to six nitrogen atoms from four azide anions and one N-methyl-1,3-propanediamine molecule in a distorted octahedral geometry. In 1, the basal-apical double μ1,1-azido bridged Cu(ii)-dimers are connected through two asymmetric μ1,3-N3 bridges to form a 1D chain in which one of the azide acts as a μ1,1,3 bridge while the other one is terminal. The structure of 2 is very similar but one of the azide ions acts as μ1,1 and the othe…
Oxo-Vanadium(IV) Dihydrogen Phosphate: Preparation, Magnetic Study, and Heterogeneous Catalytic Epoxidation
2008
A layered oxo-vanadium(IV) dihydrogen phosphate, {VO(H2PO 4)2} n has been synthesized hydrothermally and characterized by several physicochemical methods. Single-crystal X-ray analysis (crystal system, tetragonal; space group, P4/ ncc; unit cell dimensions, a = b = 8.9632(4), c = 7.9768(32) A) of {VO(H2PO4) 2} n reveals that the compound has an extended two-dimensional structure. The VO2+ moieties are connected through bridging H 2PO4 (-) ions, and this type of connection propagates parallel to the crystallographic ab plane which gives rise to a layered structure. The layers are staked parallel to the crystallographic c axis with a separation between the layers of ca. 4.0 A. Magnetic suscep…
Magnetic properties of vanadium(IV)-based extended systems: [(VO)3(μ-PO4)2(2,2′-bpy)(μ-OH2)]*1/3H2O and (VO)2H4P2O9
2013
International audience; The magnetic properties of [(VO)3(μ-PO4)2(2,2′-bpy)(μ-OH2)]1/3H2O (1) and (VO)2H4P2O9 (2), a tubular and a layered vanadium(IV) phosphates containing triply oxido bridged VIV dimers, are analyzed considering the Bleaney-Bowers S = 1/2 dimer model. In compound 1 the presence of an additional VIV connected with the VIV dimers through μ1,2-PO43− bridges is described with a Curie-Weiss type correction. This model reproduces the magnetic properties of compound 1 with g = 1.956, Jdim = −102.1 cm−1, θ = −0.4 cm−1 and Nα = 278 × 10−6 emu mol−1. In compound 2, the presence of a small percentage of paramagnetic impurity has to be considered to account for the divergence of χm …
S-shaped decanuclear heterometallic [Ni8Ln2] complexes [Ln(iii) = Gd, Tb, Dy and Ho]: theoretical modeling of the magnetic properties of the gadolini…
2014
The reaction of 8-quinolinol-2-carboaldoxime (LH2) with Ni(II) and Ln(III) salts afforded the heterometallic decanuclear compounds [Ni8Dy2(μ3-OH)2(L)8(LH)2(H2O)6](ClO4)2·16H2O (1), [Ni8Gd2(μ3-OH)2(L)8(LH)2(H2O)4(MeOH)2](NO3)2·12H2O (2), [Ni8Ho2(μ3-OH)2(L)8(LH)2(H2O)4(MeOH)2](ClO4)2·2MeOH·12H2O (3) and [Ni8Tb2 (μ3-OH)2(L)8(LH)2(MeOH)4(OMe)2]·2CH2Cl2·8H2O (4). While compounds 1-3 are dicationic, compound 4 is neutral. These compounds possess an S-shaped architecture and comprise a long chain of metal ions bound to each other. In all the complexes, the eight Ni(II) and two Ln(III) ions of the multimetallic ensemble are hold together by two μ3-OH, eight dianionic (L(2-)) and two monoanionic oxi…
Intramolecular ferro- and antiferromagnetic interactions in oxo-carboxylate bridged digadolinium(iii) complexes
2010
Two new digadolinium(III) complexes with monocarboxylate ligands, [Gd2(pac)6(H2O)4] (1) and [Gd2(tpac)6(H2O)4] (2) (Hpac = pentanoic acid and Htpac = 3-thiopheneacetic acid), have been prepared and their structures determined by X-ray diffraction on single crystals. Their structures consist of neutral and isolated digadolinium(III) units, containing six monocarboxylate ligands and four coordinated water molecules, the bridging skeleton being built by a muO(1):kappa2O(1)O(2) framework. This structural pattern has already been observed in the parent acetate-containing compound [Gd2(ac)6(H2O)4] x 4 H2O (3) whose structure and magnetic properties were reported elsewhere (L. Cañadillas-Delgado, …
Dinuclear and two- and three-dimensional gadolinium(III) complexes with mono- and dicarboxylate ligands: synthesis, structure and magnetic properties
2009
Three new gadolinium(III) complexes with carboxylate ligands of formula [Gd2(ac)6(H2O)4]·2H2O (1), [Gd2(ac)2(fum)2(H2O)4]n (2) and [Gd2(ox)(fum)2(H2O)4]n·4nH2O (3) (ac = acetate, fum = fumarate and ox = oxalate) have been prepared and their structures determined by X-ray diffraction on single crystals. The structure of 1 is made up of discrete centrosymmetric di-µ-oxo(carboxylate acetate)digadolinium(III) units with an intramolecular Gd⋯Gd separation of 4.1589(3) A. Each gadolinium atom in 1 is nine-coordinated with two water molecules and seven carboxylate-oxygen atoms from four acetate ligands building a monocapped square antiprism environment. Compound 2 exhibits a sheet-like structure, …
Charge transfer salts containing a paramagnetic cyano-complex and iodine substituted organic donor involving –I(donor)···N(anion)-interactions
2005
Abstract The preparation, crystal structures, EHT band calculation and optical properties of two new charge transfer salts, namely (DIET)2[Fe(bpca)(CN)3] (1) and (DIEDO)2[Fe(bpca)(CN)3] (2), where bpca = bis(2-pyridylcarbonyl)amide anion, DIET = diiodoethylenedithotetrathiavalene and DIEDO = diiodoethylenedioxotetrathiavalene are reported. The magnetic properties of 2 and those of the low-spin iron(III) precursor of formula (PPh4)[Fe(bpca)(CN)3]·H2O (3) were also investigated in the temperature range 1.9–205 K. Crystal data; (1): monoclinic P21, a = 8.8238(2)A, b = 13.2891(3) A, c = 18.5042(5) A, β = 91.115(1)°, Z = 2, R = 0.0710 for 7021 independent reflections with I > 2 σ(I) and (2): Mon…