Terbium Triangle Bridged by a Triazole Nitronyl Nitroxide Radical with Single-Molecule-Magnet Behavior

An unprecedented cyclic Tb^III-radical cluster, [Tb₃(hfac)₆(4-Me-3-NITtrz)₂(OH)₃] (1), has been self-assembled from Tb(hfac)₃·2H₂O and 4-Me-3-NITtrz in the presence of Cu(hfac)₂·2H₂O. Alternating-current magnetic studies show that the Tb₃ cluster displays a dual slow relaxation of magnetization behavior under a zero direct-current (dc) field and a single relaxation process under an induced dc field with an effective energy barrier of 14 K, representing the first triangle 2p-4f cluster with a slow magnetic relaxation property.

Tuning the magnetization dynamics of TbIII-based single-chain magnets through substitution on the nitronyl nitroxide radical

Two one-dimensional nitronyl nitroxide radical (NITR)-bridged lanthanide chain compounds, namely [Tb(hfac)₃(NIT-4-ThienPh)]_n (1) and [Tb(hfac)₃(NIT-5-ThienPh)]_n (2), where hfac = hexafluoroacetylacetonate, NIT-4-ThienPh = 2-(4'-phenyl-2'-thienyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide, and NIT-5-ThienPh = 2-(5'-phenyl-2'-thienyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide, were obtained with different NITRs. Alternating-current magnetic susceptibility studies show that both the compounds are single-chain magnets, while a minor change of the site of the phenyl substituent on the NITR significantly influences the magnetization dynamics. The effective magnetization reversal barrier of 1 (53 cm^-1) is more than two times higher than that of 2 (20 cm^-1) and the coercive field of 1 is also much higher than that of 2 because of minor changes in the local coordination symmetry of the Tb^III centers and the magnetic interactions between the spin carriers along the chain induced by substitution on the radical ligand.

Phosphine Oxide Ligand Based Tetrahedral CoII Complexes with Field-induced Slow Magnetic Relaxation Behavior Modified by Terminal Ligands

Two isostructural mononuclear Co^II complexes, [Co(xantpo)(NCE)₂ ] (E=S (1) and O (2); xantpo=9,9-dimethyl-4,5-bis(diphenylphosphoryl) xanthene), supported by a bidentate phosphine oxide ligand are reported. The cobalt complexes exhibit characteristic tetrahedral structures coordinated with two oxygen and two nitrogen atoms. Magnetic property measurements show their similar static magnetic behaviours but very different dynamic magnetic behaviours. Both complexes show field-induced slow magnetic relaxation behaviours, but the relaxation of 2 is much slower than that of 1. Fittings to the magnetic data and ab initio CASSCF calculations reveal significant changes in the zero field splitting (ZFS) parameters (D and E), which can be attributed to the small geometrical changes of the Co ions and the different ligand field strength of the two terminal ligands.

From mononuclear to two-dimensional cobalt(ii) complexes based on a mixed benzimidazole–dicarboxylate strategy: syntheses, structures, and magnetic properties

Three cobalt(ii) complexes with diverse structure dimensions based on a mixed benzimidazole–dicarboxylate strategy have been synthesized hydrothermally and characterized structurally and magnetically.

Five new coordination polymers with a Y-shaped N-heterocyclic carboxylic acid: structural diversity, bifunctional luminescence sensing and magnetic properties

Five novel CPs have been synthesized under solvothermal conditions. The results show that 1 and 2 present high sensing ability for NACs and Fe³⁺ ions, and there exist ferromagnetic interaction in 3/4 and antiferromagnetic interaction in 5.

Reversible structural transformation induced switchable single-molecule magnet behavior in lanthanide metal–organic frameworks

The structural transformation between Ln-MOFs 1 and 2 and the corresponding switchable “on/off” single-molecule magnet behavior have been studied.

A Water-Stable Cl@Ag14 Cluster Based Metal-Organic Open Framework for Dichromate Trapping and Bacterial Inhibition

Decoding the principles of cluster-based framework assembly at the molecular level remains a persistent challenge. Herein, we isolated and characterized a novel water-stable three-dimensional (3D) metal-organic open framework [Cl@Ag₁₄(cPrC≡C)₁₀Cl₂·(p-TOS)·1/3H₂O]_n (SD/Ag14, cPrC≡CH = cyclopropylacetylene; p-TOS = p-toluenesulfonate), which contains a chloride-templated Ag₁₄ cluster as building block. For SD/Ag14, one chloride acts as the template to shape the Ag₁₄ cluster and the other bridges the clusters to a 3D pcu-h open framework. As revealed by high resolution electrospray mass spectrometry (HRESI-MS), the Ag₁₂-Ag₁₄ species are potential cluster-based intermediates to the 3D pcu-h framework, which authenticates a preconceived idea that the 3D framework is hierarchically assembled from the silver clusters as observed in solid state. Interestingly, SD/Ag14 can be used effectively to remove the environmental pollutant Cr₂O₇^2- from wastewater through anion exchange in a single-crystal-to-single-crystal (SC-SC) transformation fashion. Furthermore, SD/Ag14 exhibits excellent antibacterial activity against Staphylococcus aureus, thus making it a potential antibacterial agent.

Coordination-Cluster-Based Molecular Magnetic Refrigerants

Coordination polymers serving as molecular magnetic refrigerants have been attracting great interest. In particular, coordination cluster compounds that demonstrate their apparent advantages on cryogenic magnetic refrigerants have attracted more attention in the last five years. Herein, we mainly focus on depicting aspects of syntheses, structures, and magnetothermal properties of coordination clusters that serve as magnetic refrigerants on account of the magnetocaloric effect. The documented molecular magnetic refrigerants are classified into two primary categories according to the types of metal centers, namely, homo- and heterometallic clusters. Every section is further divided into several subgroups based on the metal nuclearity and their dimensionalities, including discrete molecular clusters and those with extended structures constructed from molecular clusters. The objective is to present a rough overview of recent progress in coordination-cluster-based molecular magnetic refrigerants and provide a tutorial for researchers who are interested in the field.

pH-Controlled assembly of two novel Dawson-sandwiched clusters involving the in situ reorganization of trivacant α-[P2W15O56](12-) into divacant α-[P2W16O57](8.)

Modified classical trivacant Wells-Dawson α-[P2W15O56](12-) and the assembly of related sandwiched transition metal clusters are of interest, but surprisingly few reports of these materials exist because of the sensitivity of α-[P2W15O56](12-) to the assembly environment. Herein, we describe the pH-controlled assembly of two novel Dawson-sandwiched clusters, (H2bpz)6[Co2(P2W16O57)2]·22H2O (1, bpz = 3,3',5,5'-tetramethyl-4,4'-bipyrazole) and (H2bpz)6[Co3H2(P2W16O57)(P2W15O56)(H2O)]·12H2O (2), involving the in situ transformation of α-[P2W15O56](12-). Both clusters were characterized by X-ray single-crystal diffraction, FT-IR spectroscopy, UV-Visible spectroscopy, thermogravimetric analysis, powder X-ray diffraction, and elemental analyses. X-ray crystallography showed that both heteropolytungstates become divacant α-[P2W16O57](8-) and symmetrically encapsulate two edge-shared CoO6 octahedra in the interior in 1, while only one divacant α-[P2W16O57](8-) is observed in 2, which combined with another trivacant α-[P2W15O56](12-) to asymmetrically clamp three edge-shared CoO6 octahedra. The α-[P2W16O57](8-) heteropolytungstate should be generated in situ from α-[P2W15O56](12-)via self-decomposition equilibria in solution. Their electrochemical behaviors reveal characteristic multi-electron redox processes related to W(VI) centers. The electrocatalytic reduction performances toward nitrite, hydrogen peroxide, chlorate, bromate and iodate were fully measured and discussed; among these species, both clusters exhibit the best electrocatalytic activity towards the reduction of bromate. Magnetic measurements indicate weak ferromagnetic exchange interactions between Co atoms sandwiched by vacant polyoxometalates.

Spin canting, metamagnetism, and single-chain magnetic behaviour in a cyano-bridged homospin iron(II) compound

Spin canting, antiferromagnetic ordering, metamagnetism and single-chain magnetism were verified in a cyano-bridged Fe(II) compound synthesized from the pentagonal bipyramidal Fe(II) starting material in the presence of excessive BF4(-) anions.

An unusual three-dimensional Dy–Cd2 framework exhibiting single-ion magnet behavior

A framework approach was successfully performed to give a three-dimensional heterometallic compound exhibiting single-ion magnet (SIM) behavior.

An unusual water-bridged homospin CoII single-chain magnet

A 3D coordination polymer has been constructed by linking water-bridged cobalt chains via dicarboxylic ligands to show interesting SCM behaviour.