Ferromagnetice exchange in bichloride bridged Cu(II) chains: magnetostructural correlations between ordered and disordered systems

The synthesis, structure, magnetic properties, and theoretical analysis of a new phase of dichloro(2-thlaro-3-methylpyridine)copper(II) (2) and its isomorphous analogue dichloro(2bromo-3-methylpyridine)copper(II) (3) are reported. Both complexes crystallize in the orthorhombic space group Pbca and present square pyramidal Cu(II) ions bridged into chains by chloride ions with each,copper(II)-bearing a single pyridine ligand. Variable temperature magnetic Susceptibility measurements were well fit by a uniform one-dimensional ferromagnetic chain model with,2) J = 69.0(7) K, C = 0.487 emu-K/mol-Oe; 3, J = 73.9(4) K, C = 0.463 emu-K/mol-Oe = Hamiltonian). The experimental J-values were confirmed-via theOretical calculations. Comparison to a known disordered polymorph of dichloro(2-chloro-3-inethylpyridine)copper(II), 1, shows marked differences as there are significant antiferromagnetic next-nearest neighbor interactions, in 1 in addition to randomness induced by the disorder which provide a distinctly different magnetic response. The differences in magnetic behavior are attributed principally to the structural difference in the Cu(II) coordination sphere, 1 being significantly closer to trigonal-bipyramidal, whose difference changes both the nearest and next-nearest neighbor interactions

Quantification of Water Absorption and Transport in Parchment

AbstractNeutron radiography was utilized to quantify water absorption and desorption in parchment at the High Flux Isotope Reactor CG-1D imaging facility at Oak Ridge National Laboratory (ORNL). Sequential 60s radiographs of sections of a 15th century parchment were taken as the parchment underwent wetting and drying cycles. This provided time-resolved visualization and quantification of water absorption and transport in parchment

Formation of Defect-Dicubane-Type Ni II 2 Ln III 2 (Ln = Tb, Er) Clusters: Crystal Structures and Modeling of the Magnetic Properties

In the field of molecular nanoclusters, cubane and defect-dicubane, or butterfly structures, are typical examples of tetranuclear metal core architectures. In this work, a halogenated and anionic Schiff-base ligand (L2–) is utilized as it is predisposed to chelate within a cluster core to both 3d and 4f metal ions, in different binding configurations (H2L = 4-chloro-2-(2-hydroxy-3-methoxybenzyliden amino)phenol). The phenolate oxygen atoms of the deprotonated ligand can act in μ-O and μ3-O bridging binding modes for the intramolecular assembly of metal ions. Based on that, two tetranuclear and isostructural compounds [Ni2Tb2(L)4(NO3)2(DMF)2]·2CH3CN (1) and [Ni2Er2(L)4(NO3)2(DMF)2]·0.5CH3CN (2) were synthesized and structurally characterized. Magnetic susceptibility and magnetization data indicate the occurrence of dominant intramolecular ferromagnetic interactions between the spin centers. Particular emphasis is given to the theoretical description of the magnetic behavior, taking into account the Ln–Ni and Ni–Ni coupling paths and the magnetic anisotropy of the LnIII and NiII ions. The study is distinguished for its discussion of two distinct models, whereby model A relies on the uniaxial B20 Stevens term describing the lanthanide anisotropy and model B is based on point-charge model calculations. Importantly, the physical meaning of the obtained parameters for both models was critically scrutinized

Ferromagnetic Exchange in Bichloride Bridged Cu(II) Chains: Magnetostructural Correlations between Ordered and Disordered Systems

The synthesis, structure, magnetic properties, and theoretical analysis of a new phase of dichloro­(2-chloro-3-methylpyridine)­copper­(II) (<b>2</b>) and its isomorphous analogue dichloro­(2-bromo-3-methylpyridine)­copper­(II) (<b>3</b>) are reported. Both complexes crystallize in the orthorhombic space group <i>Pbca</i> and present square pyramidal Cu­(II) ions bridged into chains by chloride ions with each copper­(II) bearing a single pyridine ligand. Variable temperature magnetic susceptibility measurements were well fit by a uniform one-dimensional ferromagnetic chain model with <b>2</b>, <i>J</i> = 69.0(7) K, <i>C</i> = 0.487 emu-K/mol-Oe; <b>3</b>, <i>J</i> = 73.9(4) K, <i>C</i> = 0.463 emu-K/mol-Oe (<i>H</i> = −<i>J</i>Σ<i>S</i>_<i>i</i>·<i>S</i>_<i>j</i> Hamiltonian). The experimental <i>J</i>-values were confirmed via theoretical calculations. Comparison to a known disordered polymorph of dichloro­(2-chloro-3-methylpyridine)­copper­(II), <b>1</b>, shows marked differences as there are significant antiferromagnetic next-nearest neighbor interactions in <b>1</b> in addition to randomness induced by the disorder which provide a distinctly different magnetic response. The differences in magnetic behavior are attributed principally to the structural difference in the Cu­(II) coordination sphere, <b>1</b> being significantly closer to trigonal–bipyramidal, whose difference changes both the nearest and next-nearest neighbor interactions

Ferromagnetic Exchange in Bichloride Bridged Cu(II) Chains: Magnetostructural Correlations between Ordered and Disordered Systems

The synthesis, structure, magnetic properties, and theoretical analysis of a new phase of dichloro­(2-chloro-3-methylpyridine)­copper­(II) (<b>2</b>) and its isomorphous analogue dichloro­(2-bromo-3-methylpyridine)­copper­(II) (<b>3</b>) are reported. Both complexes crystallize in the orthorhombic space group <i>Pbca</i> and present square pyramidal Cu­(II) ions bridged into chains by chloride ions with each copper­(II) bearing a single pyridine ligand. Variable temperature magnetic susceptibility measurements were well fit by a uniform one-dimensional ferromagnetic chain model with <b>2</b>, <i>J</i> = 69.0(7) K, <i>C</i> = 0.487 emu-K/mol-Oe; <b>3</b>, <i>J</i> = 73.9(4) K, <i>C</i> = 0.463 emu-K/mol-Oe (<i>H</i> = −<i>J</i>Σ<i>S</i>_<i>i</i>·<i>S</i>_<i>j</i> Hamiltonian). The experimental <i>J</i>-values were confirmed via theoretical calculations. Comparison to a known disordered polymorph of dichloro­(2-chloro-3-methylpyridine)­copper­(II), <b>1</b>, shows marked differences as there are significant antiferromagnetic next-nearest neighbor interactions in <b>1</b> in addition to randomness induced by the disorder which provide a distinctly different magnetic response. The differences in magnetic behavior are attributed principally to the structural difference in the Cu­(II) coordination sphere, <b>1</b> being significantly closer to trigonal–bipyramidal, whose difference changes both the nearest and next-nearest neighbor interactions

Ferromagnetic Exchange in Bichloride Bridged Cu(II) Chains: Magnetostructural Correlations between Ordered and Disordered Systems

The synthesis, structure, magnetic properties, and theoretical analysis of a new phase of dichloro­(2-chloro-3-methylpyridine)­copper­(II) (<b>2</b>) and its isomorphous analogue dichloro­(2-bromo-3-methylpyridine)­copper­(II) (<b>3</b>) are reported. Both complexes crystallize in the orthorhombic space group <i>Pbca</i> and present square pyramidal Cu­(II) ions bridged into chains by chloride ions with each copper­(II) bearing a single pyridine ligand. Variable temperature magnetic susceptibility measurements were well fit by a uniform one-dimensional ferromagnetic chain model with <b>2</b>, <i>J</i> = 69.0(7) K, <i>C</i> = 0.487 emu-K/mol-Oe; <b>3</b>, <i>J</i> = 73.9(4) K, <i>C</i> = 0.463 emu-K/mol-Oe (<i>H</i> = −<i>J</i>Σ<i>S</i>_<i>i</i>·<i>S</i>_<i>j</i> Hamiltonian). The experimental <i>J</i>-values were confirmed via theoretical calculations. Comparison to a known disordered polymorph of dichloro­(2-chloro-3-methylpyridine)­copper­(II), <b>1</b>, shows marked differences as there are significant antiferromagnetic next-nearest neighbor interactions in <b>1</b> in addition to randomness induced by the disorder which provide a distinctly different magnetic response. The differences in magnetic behavior are attributed principally to the structural difference in the Cu­(II) coordination sphere, <b>1</b> being significantly closer to trigonal–bipyramidal, whose difference changes both the nearest and next-nearest neighbor interactions