1,721,127 research outputs found
Two-dimensional metal-organic frameworks: a system with competing chelating ligands
No full textWe report the synthesis, structure, and magnetism of two coordination polymers with a designed network topology. These isostructural materials are hydrothermally crystallized having a composition of M(en)(ox) (en = ethylenediamine, ox = oxalate, M = Co(II) 1 and Ni(II) 2). The structures show a rare bridging mode of ethylenediamine which links linear [M(ox)]∞ chains into an oblique two-dimensional network. Both compounds show antiferromagnetic interactions behaving as one-dimensional magnets. The magnetism of 1 is consistent with an S = 3/2 chain affected by spin−orbit coupling (g = 2.814(2), J/kB = −16.03(3) K, D/kB = 86.2(4) K), while 2 is a candidate Haldane antiferromagnet (g = 2.194(2), J/kB = −39.3(1), Eg/kB = 16.5 K). We discuss the use of models for S = 3/2 antiferromagnetic chains and present our own polynomial for Heisenberg S = 3/2 antiferromagnetic chains
A new series of layered transition metal oxalates: hydrothermal synthesis, structural and magnetic studies
No full textThe hydrothermal synthesis and crystallographic study of a new family of isostructural transition metal oxalate compounds, Ba2M2(ox)(3)Cl-2(H2O)(4) (M = Mn(II) (1), Fe(II) (2) or Co(II) (3)) is reported. The crystal structure has C2/c symmetry and contains two types of oxalate. These dianionic ligands bridge the transition metal ions in two different modes, which together form a 2-D net comprised of linked chains of transition metal ions. The iron derivative shows strong evidence of antiferromagnetic coupling interactions and significant short-range magnetic order at low temperatures but there is no evidence of long-range ordering above 2 K. Attempts to fit the observed magnetic susceptibility to several approximate models is reviewed. The Co derivative also shows antiferromagnetic coupling and additionally appears to have a magnetic phase transition at about 11(1) K
trans-bis(2-aminoanilinium-kappa N-2)bis(oxalato-kappa O-2,O')copper(II)
Full text linkThe title compound, [Cu(C2O4)(2)(C6H9N2)(2)], crystallizes in the space group P2(1)/c, with the Cu atom located at a centre of symmetry. It is a neutral coordination complex in which the metal exhibits a tetragonally elongated octahedral trans-CuO4N2 coordination environment. Extensive intermolecular hydrogen bonding between the oxalate anions and the ammonium cations determines the molecular packing in the crystal
Stabilization of discrete [Cu(C2O4)(2)(H2O)(2)](2-) dianions in the solid state by an extensive hydrogen bonded network
No full textThe dominant species in aqueous copper(II) solutions containing a high concentration of oxalate (ox) is trans[Cu(ox)(2)(H2O)(2) ](2-), yet the ability of the oxalate anion to bridge metal ions means that very few examples of this isolated anion are seen in solid state structures. The structure of [pipH(2)](2+)[Cu(ox)(2)(H2O)(2)](2-). 2H(2)O (pip = piperazine) (1) comprises discrete ions held in a complex 3-dimensional hydrogen bonded network
Ferromagnetic coupling in a heptanuclear nickel cluster with a vertex-shared dicubane structure
No full textHydrothermal synthesis under basic conditions has given a new cluster compound, Ni-7(OH)(8)(ox)(3)(pip)(3) (ox = oxalate; pip = piperazine). This hybrid material comprises inorganic Ni-7(OH)(8) clusters, which have a vertex-shared dicubane structure. These units are held together in a 3-dimensional coordination network by organic bridging ligands. Magnetic susceptibility studies suggest a ferromagnetic coupling within the cluster and an antiferromagnetic interaction between neighbouring Ni-7 units. At low temperatures the material appears to undergo a magnetic phase transition to an ordered antiferromagnetic state with T-N = 17 K
Tetra-n-butylamine(carbonato-kappa O-2,O')cobalt(III)n-butylcarbamate dihydrate
Full text linkThe title compound, [Co(CO3)(C4H11N)4](C5H10NO2)·2H2O, is a coordination complex with an N4O2 coordination sphere around the central CoIII ion. The small bite angle of the chelating carbonate causes a distortion of the octahedral geometry to an approximately C2v local symmetry. Hydrogen-bonding between the carbonate, carbamate and amine groups, and the water of crystallization, results in a complex two-dimensional network
Poly[methylamine-mu-oxalato-copper(II)]
Full text linkThe six-coordinate copper(II) ions in the title compound, [Cu(C2O4)(CH5N)], experience a Jahn-Teller distortion. The structure is a two-dimensional coordination network, with three crystallographically independent oxalate ions, two of them centrosymmetric, bridging Cu-II ions in three different coordination modes. Each Cu ion is also coordinated by methyl-amine which is involved in both intra- and inter-layer hydrogen bonding
Topological ferrimagnetism and superparamagnetic-like behaviour in a disordered homometallic coordination network
Full text linkCrystals of a cobalt(II) 3-amino-1,2,4-triazolate; Co2Cl(C2N4H3)3, 1 can be formed from a hydrothermal synthesis. X-Ray crystallography shows an extended 3-dimensional network structure within a hexagonal space group with a = 9.9655(7) and c = 7.7523(7) Å. The data reveal an orientational disorder to the ligand. Structural considerations suggest that the ligand orientation is strongly correlated in 1-dimension, but the nature and length scale of the 2-dimensional order is not obvious. The structure is discussed in terms of three key structural models, two of which are crystallographically ordered, while the third is disordered in 2-dimensions. The effect of ligand orientation on the network topology has profound effects on the expected magnetic behaviour, with the two fully ordered models having either antiferromagnetic or ferrimagnetically ordered ground states. The magnetism of 1 is complex. It shows an antiferromagnetically coupled paramagnetic phase above 5.3 K. Below 4.5 K we see a ferrimagnetically ordered state (Hcoer = 50 Oe, Mrem = 1830 Oe cm3 mol–1, Msat = 3450 Oe cm3 mol–1 at 2 K). In the intermediate temperature range 4.5 to 5.3 K we see unusual behaviour with evidence of rapid, low-energy relaxation of the magnetisation. The unusual relationship between the structure and the magnetism of 1 is discussed in detail
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