Two manganese(II) coordination polymers driven by (iso)nicotinoyl-hydrazone blocks and pseudohalide ancillary ligands: syntheses, structural features, and magnetic properties

<p>Two coordination polymers, [Mn₂(μ-L¹)₂(μ-N₃)₂]_n (<b>1</b>) and [Mn(μ-HL²)(SCN)₂]_n (<b>2</b>), were assembled in a single-pot from MnCl₂·4H₂O, HL¹ (2-acetylpyridine isonicotinoylhydrazone) or HL² (2-acetylpyridine nicotinoylhydrazone) and ancillary ligand sources (NaN₃ or NH₄NCS). The products were fully characterized, including by single-crystal X-ray diffraction, which revealed a 2-D metal–organic layer in <b>1</b> and a 1-D zigzag coordination chain in <b>2</b>. Both <b>1</b> and <b>2</b> are constructed from six-coordinate Mn(II) nodes that adopt distorted octahedral (MnN₅O) environments; the adjacent nodes are driven by the μ-L¹ and μ-N₃ linkers in <b>1</b> or μ-HL² linkers in <b>2</b> to form different metal–organic networks. Their topological classification was performed, disclosing the <b>hcb</b> and <b>2C1</b> topology in <b>1</b> and <b>2</b>, respectively. Different weak non-covalent interactions promote dimensionality extension. Variable-temperature magnetic susceptibility measurements were carried out, revealing weak ferromagnetic and antiferromagnetic interactions in <b>1</b> and <b>2</b>, respectively.</p

High Nuclearity Assemblies and One-Dimensional (1D) Coordination Polymers Based on Lanthanide–Copper 15-Metallacrown‑5 Complexes (Ln^III = Pr, Nd, Sm, Eu)

Complexes {[LnCu₅(GlyHA)₅(<i>m</i>-bdc)­(H₂O)_4–<i>x</i>]₂[LnCu₅(GlyHA)₅(SO₄)­(<i>m</i>-bdc)­(H₂O)₄]₂}·(30 + 2<i>x</i>)­H₂O (where GlyHA^2– = glycinehydroxamate, <i>m</i>-bdc^2– = <i>m</i>-phthalate; Ln = Pr and <i>x</i> = 0.21 for compound <b>1</b>, or Ln = Sm and <i>x</i> = 0.24 for <b>3</b>) and one-dimensional (1D) coordination polymers {[NdCu₅(GlyHA)₅(H₂O)₅(<i>m</i>-bdc)]<i>_nn</i>[NdCu₅(GlyHA)₅(H₂O)₄(μ-CO₃)­(<i>m</i>-bdc)]}·13<i>n</i>H₂O (<b>2</b>) and {[EuCu₅(GlyHA)₅(H₂O)₃]­(<i>m</i>-bdc)₂[EuCu₅(GlyHA)₅(<i>m</i>-bdc)­(H₂O)₃]}_<i>n</i>·17<i>n</i>H₂O (<b>4</b>) were obtained starting from the 15-metallacrown-5 complexes {[LnCu₅(GlyHA)₅(SO₄)­(H₂O)_6.5]}₂(SO₄)·6H₂O (Ln = Pr, Nd, Sm, Eu) by the partial or complete metathesis of sulfate anions with <i>m</i>-phthalate. Compounds <b>1</b> and <b>3</b> contain unprecedented quadruple-decker neutral metallacrown assemblies, where the [LnCu₅(GlyHA)₅]³⁺ cations are linked by <i>m</i>-phthalate dianions. In contrast, in complexes <b>2</b> and <b>4</b>, these components assemble into 1D chains of coordination polymers, the adjacent {[NdCu₅(GlyHA)₅(H₂O)₅(<i>m</i>-bdc)]⁺}<i>_n</i> 1D chains in <b>2</b> being separated by discrete [NdCu₅(GlyHA)₅(H₂O)₄(μ-CO₃)­(<i>m</i>-bdc)]}⁻ complex anions. The crystal lattices of <b>2</b> and <b>4</b> contain voids filled by solvent molecules. Desolvated <b>4</b> is able to absorb up to 0.12 cm³/g of methanol vapor or 0.04 cm³/g of ethanol at 293 K. The isotherm for methanol absorption by compound <b>4</b> is consistent with a possible “gate opening” mechanism upon interaction with this substrate. The χ_M<i>T</i> vs <i>T</i> data for complexes <b>1</b>–<b>4</b> and their simpler starting materials {[LnCu₅(GlyHA)₅(SO₄)­(H₂O)_6.5]}₂(SO₄)·6H₂O (Ln­(III) = Pr, Nd, Sm, Eu) were fitted using an additive model, which takes into account exchange interactions between lanthanide­(III) and copper­(II) ions in the metallamacrocycles via a molecular field model. The exchange interactions between adjacent Cu­(II) ions in metallacrown fragments were found to fall in the range of −47 < <i>J</i>_Cu–Cu < −63 cm^–1. These complexes are the first examples of a Ln­(III)-Cu­(II) 15-metallacrowns-5 (Ln­(III) = Pr, Nd, Sm, Eu), for which values of exchange parameters have now been reported

Thickness-Dependent Crossover from Charge- to Strain-Mediated Magnetoelectric Coupling in Ferromagnetic/Piezoelectric Oxide Heterostructures

Magnetoelectric oxide heterostructures are proposed active layers for spintronic memory and logic devices, where information is conveyed through spin transport in the solid state. Incomplete theories of the coupling between local strain, charge, and magnetic order have limited their deployment into new information and communication technologies. In this study, we report direct, local measurements of strain- and charge-mediated magnetization changes in the La_0.7Sr_0.3MnO₃/PbZr_0.2Ti_0.8O₃ system using spatially resolved characterization techniques in both real and reciprocal space. Polarized neutron reflectometry reveals a graded magnetization that results from both local structural distortions and interfacial screening of bound surface charge from the adjacent ferroelectric. Density functional theory calculations support the experimental observation that strain locally suppresses the magnetization through a change in the Mn-e_g orbital polarization. We suggest that this local coupling and magnetization suppression may be tuned by controlling the manganite and ferroelectric layer thicknesses, with direct implications for device applications