Spin Canting and Slow Relaxation in a 3D Pillared Nickel−Organic Framework

Metamagnetism and canted antiferromagnetic ordering in two monomeric CoII complexes with 1-(2-pyrimidyl)piperazine. Hirshfeld surface analysis and theoretical studies

Here we present the magnetic properties of two cobalt complexes formulated as: [Co(SCN)2(L)2] (1) and (H2L)2[Co(SCN)4]·H2O (2) (L = 1-(2-pyrimidyl)piperazine). The two compounds contain isolated tetrahedral CoII complexes with important intermolecular interactions that lead to the presence of a canted antiferromagnetic order below 11.5 and 10.0 K, with coercive fields at 2 K of 38 and 68 mT, respectively. Theoretical calculations have been used to explain this behaviour. Hirshfeld surface analysis shows the presence of strong intermolecular interactions in both compounds. The crystal geometries were used for geometry optimization using the DFT method. From the topological properties, electrostatic potential maps and molecular orbital analysis, information about the noncovalent interaction and chemical reactivity was obtained.

Two Metal-Organic Frameworks Based on Hexanuclear Cobalt-Hydroxyl Clusters or a Manganese-Hydroxyl Chain from Triangular [MII3(μ3-OH)] (M = Co and Mn) Units: Antiferromagnetic and Spin-Canting Antiferromagnetic Ordering with Soft-Magnetic Behavior

Three-dimensional highly connected isonicotinic acid-base metal-organic frameworks (MOFs), [Co^II₆(μ₃-OH)₂(in)₇(HCOO)₃H₂O]·4DMF (1) and [Mn^II₃(μ₃-OH)(in)₃(CH₃COO)₂] (2) (Hin = isonicotinic acid), have been successfully prepared. Compounds 1 and 2 were constructed from planar Co₆ cluster SBUs or rare 1D manganese-hydroxyl chain SBUs, respectively. Both SBUs contain triangular M^II₃(OH) (M = Co and Mn) central units, which are connected by rare syn,anti,syn,anti- and syn,syn,anti-coordinated formic acid or acetic acid. Both compounds 1 and 2 have good thermal stability, while compound 2 also exhibits an extraordinarily high moisture stability. Magnetic studies demonstrate that 1 shows antiferromagnetic behavior, and 2 exhibits spin-canting antiferromagnetic ordering with soft-magnetic behavior.

Magnetic Phase Transitions in a Ni4 O4 -Cubane-Based Metal-Organic Framework

An unprecedented spin cluster‐based network architecture {[Ni^II₂(pdaa)(OH)₂(H₂O)]_n (H₂pdaa=1,4‐phenylene diacetic acid)}, comprising 1D linear chains of Ni^II ions crosslinked via Ni₄O₄ cubanes, forms under hydrothermal conditions; this 3D coordination network exhibits magnetic ordering at 23.9 K as well as a second magnetic ordering process at 2.8 K likely associated with a structural phase transition.

A Three-Dimensional Nickel(II) Framework from a Semi-Flexible Bipyrimidyl Ligand Showing Weak Ferromagnetic Behavior

A semi-flexible bipyrimidyl ligand, 5,5'-bipyrimidin (bpym), was used for the self-assembly of a transition metal coordination polymer, resulting in the formation of a nickel(II) compound, [Ni(Br)₂(bpym)₂]n (1) with a three-dimemsional (3D) structure. Single-crystal X-ray analysis showed that compound 1 crystallizes in the monoclinic space group C2/c and the structure represents a 3D (4,4)-connected bbe topological framework constructed of nickel(II) ions, twisted cis-μ-bpym and planar trans-μ-bpym groups. Magnetic characterization revealed that 1 shows antiferromagnetic coupling between the pyrimidyl-bridged Ni(II) ions along with weak ferromagnetism due to spin canting with a magnetic ordering below Tc = 3.4 K.

Syntheses, structures, and magnetic properties of three new cyano-bridged heterobimetallic chains based on [Fe(Tp*)(CN)3]−

Three, new, one-dimensional (1D) heterobimetallic cyano-bridged chain complexes of squares were prepared. The simultaneous presence of magnetic and porous properties have been found in compound 1–3.

A chiral coordination polymer with double coaxially nested helical chains exhibiting spin-canting antiferromagnetism

A chiral coordination polymer is reported, which contains rarely two types of double coaxially nested helical chains, exhibiting spin-canting antiferromagnetism.

Field-induced dynamic magnetic behaviour of a canted weak ferromagnetic chain material

A 1-D [Mn^III₃O] based magnetic chain material amazingly exhibits the coexistence of spin-glass, spin-canting, and metamagnetic behaviours as well as slow relaxation of magnetization under different applied magnetic fields.

A series of multidimensional MOFs incorporating a new N-heterocyclic building block: 5,5′-di(pyridin-4-yl)-3,3′-bi(1,2,4-triazole)

By using a new N-heterocyclic building block: 4,4′-H₂dbpt, six novel coordination polymers with diversiform connectivity from one to three dimensional were constructed and characterized by X-ray crystallography successfully.

Synthesis, crystal structure and magnetic properties of two alternating double μ1,1 and μ1,3 azido bridged Cu(ii) and Ni(ii) chains

Two new alternating double μ_1,1 and μ_1,3 azido bridged 1D Cu(ii) and Ni(ii) complexes have been synthesized and their magnetic data were fitted to an alternating ferro/antiferromagnetic chain model.

Coordination assemblies of the MII-tm/bpt (M = Zn/Cd/Co/Ni) mixed-ligand system: positional isomeric effect, structural diversification and properties

Six new coordination polymers with three positional isomeric bpt ligands and trimellitic acid (H₃tm), have been synthesized and characterized. They present diverse architectures. These results indicate that the versatile coordination modes of tm and the isomeric nature of bpt play crucial roles in modulating the structural topologies of these complexes.

Two Ni(II) Coordination Polymers Constructed with a Bent Connector: Crystal Structures and Magnetic Properties

The hydrothermal reactions of a bent ligand, 1H-3,5-bis(4-pyridyl)-1,2,4-triazole (bpt), with Ni(II) ions as well as two carboxylate co-ligands yielded two new Ni(II) coordination polymers, {[Ni2(bptc)(bpt)2(H2O)2]·9H2O}n and [Ni(hb)2(bpt)2(H2O)]n (H4bptc = 3,3’,4,4′-benzophenone-tetracarboxylate acid, Hhb = p-Hydroxybenzoate acid). In the first complex, bptc acts as a μ4-bridge to link metal centres, forming a two-dimensional (2-D) layer architecture. The 2-D layer is further connected by bpt pillars to generate a 3-D non-interpenetrating open framework with a 4-connected 64.82 topology. A magnetic study revealed the occurrence of a weak ferromagnetic interaction within the Ni(II) centres. In the second complex, adjacent metal centres are connected by water molecules to furnish a metal–water chain, in which hb and bpt are both terminal ligands.

Triaqua-(cyclo-hex-4-ene-1,2-dicarboxyl-ato-κO(1))(1,10-phenanthroline-κ(2)N,N')cobalt(II)

In the title compound, [Co(C(8)H(8)O(4))(C(12)H(8)N(2))(H(2)O)(3)], the Co(II) atom is coordinated by two N atoms from a bidentate 1,10-phenanthroline ligand, one O atom from a monodentate 4-cyclo-hexene-1,2-dicarboxyl-ate ligand and three water O atoms in a distorted octa-hedral geometry. The mononuclear mol-ecules are engaged in extensive intra- and inter-molecular O-H⋯O hydrogen-bonding inter-actions and π-π stacking inter-actions [centroid-centroid distance = 3.784 (3) Å], forming a three-dimensional supra-molecular network.

Cu(II) Coordination Architectures with Two Positionally Isomeric Triazole–Bipyridine Ligands

The Cu(II) coordination polymer, {[Cu( p-bdc)(4,4′-bpt)]}n shows a 2D layer structure bridged by a p-bdc anion and the polymer {[Cu(H2btc)(3,3′-bpt)2(H2O)2]·2H2O}n, whose thermal stability has been briefly investigated, shows a 1D chain structure bridged by an H2btc anion. [ p-H2bdc = 1,4-benzenedicarboxylate acid, H4btc = 1,2,4,5-benzenetetracarboxylic acid, 4,4′-bpt = 1H-3,5-bis(4-pyridyl)-1,2,4-triazole, 3,3′-bpt = 1H-3,5-bis(3-pyridyl)-1,2,4-triazole] Both complexes have been prepared by the reaction of the relevant carboxylate acid and positional isomeric triazole–bipyridine ligand with Cu(II) salts under hydrothermal conditions. Both structures are further extended through intermolecular interaction to form 3D supramolecular frameworks.

Diaqua-[3,5-bis-(4-pyrid-yl)-1H-1,2,4-triazole-κN](pyridine-2,6-dicarboxyl-ato-κO,N,O)nickel(II)

In the title compound, [Ni(C₇H₃NO₄)(C₁₂H₉N₅)(H₂O)₂], the Ni^II atom is coordinated in a distorted octa­hedral geometry by one N and two O atoms from a pyridine-2,6-dicarboxyl­ate ligand, one N atom from a 3,5-bis­(4-pyrid­yl)-1H-1,2,4-triazole ligand in equatorial positions and two water mol­ecules in axial positions. The crystal packing is consolidated by inter­molecular O—H⋯O, O—H⋯N and N—H⋯O hydrogen bonds.

Diaquabis(3-nitrobenzoato-κO1)bis[1H-5-(3-pyridyl)-3-(4-pyridyl)-1H-1,2,4-triazole-κN5]cobalt(II) dihydrate

In the centrosymmetric title compound, [Co(C₇H₄NO₄)₂(C₁₂H₉N₅)₂(H₂O)₂]·2H₂O, the Co^II atom, located on an inversion center, is coordinated by two N atoms [Co—N = 2.155 (3) Å] and four O atoms [Co—O = 2.099 (2)–2.117 (3) Å] in a distorted octa­hedral geometry. Inter­molecular N—H⋯O, O—H⋯N and O—H⋯O hydrogen bonds link the components into a three-dimensional supramolecular framework.