Non-traditional thermal behavior of Co(ii) coordination networks showing slow magnetic relaxation

Three new Co(ii) coordination polymers show the DC magnetic data consistent with the S = 3/2 spin system with large zero-field splitting D > 0, which was confirmed by HF EPR and FIRMS measurements.

Magneto-structural diversity of Co(ii) compounds with 1-benzylimidazole induced by linear pseudohalide coligands

The magneto-structural diversity of 1-benzylimidazole-containing cobalt(ii) compounds with linear pseudohalide ions (NCS⁻, NCO⁻, and N₃⁻) is explored.

Crystal structure and photoluminescence properties of catena-poly[[bis-(1-benzyl-1H-imidazole-κN 3)cadmium(II)]-di-μ-azido-κ4 N 1:N 3]

The crystal structure and photoluminescence properties of a new one-dimensional Cd^II coordination polymer constructued by azide and 1-benzyl­imidazole (bzi) are reported.

The new title one-dimensional Cd^II coordination polymer, [Cd(C₁₀H₁₀N₂)₂(μ_1,3-N₃)₂]_n, has been synthesized and structurally characterized by single-crystal X-ray diffraction. The asymmetric unit consists of a Cd^II ion, one azide and one 1-benzyl­imidazole (bzi) ligand. The Cd^II ion is located on an inversion centre and is surrounded in a distorted octa­hedral coordination sphere by six N atoms from four symmetry-related azide ligands and two symmetry-related bzi ligands. The Cd^II ions are linked by double azide bridging ligands within a μ_1,3-N₃ end-to-end (EE) coordination mode, leading to a one-dimensional linear structure extending parallel to [100]. The supra­molecular framework is stabilized by the presence of weak C—H⋯N inter­actions, π–π stacking [centroid-to-centroid distance of 3.832 (2) Å] and C—H⋯π inter­actions between neighbouring chains.

A difunctional azido-cobalt(ii) coordination polymer exhibiting slow magnetic relaxation behaviour and high-energy characteristics with good thermostability and insensitivity

A novel one-dimensional azido-cobalt(ii) compound, [Co2(1-mbt)2(N3)4]n (1) (1-mbt = 1-((2-propyl-imidazol-1-yl)methyl)-benzo[1,2,3]triazole), was solvothermally synthesized. X-ray crystal structure analysis demonstrates that two crystallographically independent Co(ii) atoms in the asymmetrical unit of compound 1 exhibit a rectangular pyramid geometry. The 3D supermolecular network of 1 consists of well-isolated 1D metal chains in which the azido bridging ligands assume an unusual pattern of combination with the Co(ii) centre as the sign of [-EE-EO-EO-EO-]n. The various coordination modes of the azido anion are responsible for different magnetic exchanges between the adjacent Co(ii) ions. The end-to-end (EE) mode mediates the antiferromagnetic coupling, whereas the end-on (EO) manner contributes to the ferromagnetic interaction. Magneto-structural relationships are discussed with the aid of theoretical calculations which are employed to find the potential single-ion magnetic anisotropy and reproduce the observed magnetic coupling properly. Alternating current magnetic susceptibility measurements reveal that 1 features a typical behaviour of field-induced slow magnetic relaxation. Energetic characterization evidences that the resulting compound possesses satisfactory detonation properties, superior lack of sensitivity and thermostability owing to the high nitrogen content (N% = 40.10%) and a coherent intrachain configuration. The kinetic parameters of the exothermic processes for 1 are investigated by the Kissinger method and the Ozawa method. We note that 1 has potential application prospects as a new generation of environmentally friendly high-energy materials based on this nitrogen-rich and oxygen-free system. In addition, the compound is developed as a practical additive to promote the thermal decomposition of ammonium perchlorate (AP) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). The finding in this work highlights an example of effective development of advanced magneto-energetic materials.

Structural diversity and magnetic properties of six cobalt coordination polymers based on 2,2'-phosphinico-dibenzoate ligand

Six novel Co(ii) coordination polymers, namely, [Co₁₀L₆(OH)₂(H₂O)₉]·10.5H₂O (1), [Co₃L₂(3-abpt)₂]·4H₂O (2), [Co₃L₂(4-azpy)₂(H₂O)₂(EtOH)] (3), [Co₃L₂(4,4'-bipy)₂(H₂O)₂(MeCN)] (4), [Co₃L₂(4,4'-bipy)₂] (5), and [Co₅L₂(OH)₂(ina)₂(H₂O)₂] (6) (H₃L = 2,2'-phosphinico-dibenzoic acid, 3-abpt = 4-amino-3,5-bis(3-pyridyl)-1,2,4-triazole, 4-azpy = 4,4'-azobispyridine, 4,4'-bipy = 4,4'-bipyridine, Hina = isonicotinic acid), have been hydrothermally synthesized and their magnetic properties have been characterized. The L^3- anion displays six types of coordination modes in the compounds. Compound 1 exhibits a novel 1D ladder-like structure, which consists of non-centrosymmetric Co₁₀ units. Compounds 2-4 comprise 2D networks assembled from Co₃L₂ chains and N-heterocyclic linkers. Compound 5 comprises a 3D framework built from six neighboring parallel Co₃L₂ ladders bridged by 4,4'-bipy linkers. Compound 6 features a 3D framework that exhibits pcu topology with the Schläfli symbol of (4¹²·6³) using a pentanuclear [Co₅(OH)₂]⁸⁺ cluster as the node. Variable-temperature magnetic susceptibility studies indicate that the six coordination polymers exhibit remarkable magnetic behavior such as spin-canted antiferromagnetism and spin glass, which were found to coexist in compound 6.

Reversible crystal-to-amorphous structural transformations and magnetic variations in single end-on azide-bridged MII (M = Mn, Ni) coordination polymers

Azide-bridged coordination polymers undergo reversible crystal-to-amorphous phase transformations during the hydration–dehydration process.

Two isomorphous azide/formate Mn(ii) coordination polymers show spin-canted antiferromagnetism only in the formate system

We reported two isomorphous azide/formate Mn^II complexes: the azide complex had normal antiferromagnetic coupling, while a canted antiferromagnet with a Néel temperature of T_N = 38.5 K was obtained in the formate system.

Diversified magnetic behaviors of new nickel(ii) and copper(ii) azido coordination polymers templated by diethyl or triethyl amines

The reactions of Ni^II or Cu^II ions with N₃⁻ anions in the presence of templated diethyl or triethyl amines afford three new azido-bridged coordination polymers, which exhibit metamagnetism, spin glass and canted ferromagnetism, respectively.