Fine Tuning the Energy Barrier of Molecular Nanomagnets via Lattice Solvent Molecules

A Pair of Multifunctional Cu(II)-Dy(III) Enantiomers with Zero-Field Single-Molecule Magnet Behaviors, Proton Conduction Properties and Magneto-Optical Faraday Effects

Multifunctional materials with a coexistence of proton conduction properties, single-molecule magnet (SMM) behaviors and magneto-optical Faraday effects have rarely been reported. Herein, a new pair of Cu(II)-Dy(III) enantiomers, [DyCu2(RR/SS-H2L)2(H2O)4(NO3)2]·(NO3)·(H2O) (R-1 and S-1) (H4L = [RR/SS] -N,N'-bis [3-hydroxysalicylidene] -1,2-cyclohexanediamine), has been designed and prepared using homochiral Schiff-base ligands. R-1 and S-1 contain linear Cu(II)-Dy(III)-Cu(II) trinuclear units and possess 1D stacking channels within their supramolecular networks. R-1 and S-1 display chiral optical activity and strong magneto-optical Faraday effects. Moreover, R-1 shows a zero-field SMM behavior. In addition, R-1 demonstrates humidity- and temperature-dependent proton conductivity with optimal values of 1.34 × 10-4 S·cm-1 under 50 °C and 98% relative humidity (RH), which is related to a 1D extended H-bonded chain constructed by water molecules, nitrate and phenol groups of the RR-H2L ligand.

Asymmetric Assembly of Chiral Lanthanide(III) Tetranuclear Cluster Complexes Using Achiral Mixed Ligands: Single-molecule Magnet Behavior and Magnetic Entropy Change

It is challenging to use achiral ligands to spontaneously construct chiral molecular magnets. In this work, two new Ln₄ cluster complexes based on N,N'-(1,3-propanediyl)bis[N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]amine] (H₆L) have been assembled, which are crystallized in a chiral space group due to the asymmetric distribution of acetate (OAc^-) groups and hexafluoroacetylacetonate (F₆acac^-) groups on both sides of the parallelogram-like Ln₄ core. Complex 1, [Dy₄(H₃L)₂(OAc)₃(F₆acac)₃]·5MeOH·2H₂O, exhibits single-molecule magnet properties at the zero field with the U _eff/k value of 48.4 K; notably, besides the Orbach process, the Raman process is also prominent for the magnetic relaxation of 1. Complex 2, [Gd₄(H₃L)₂(OAc)₃(F₆acac)₃]·4MeOH·2.5H₂O, displays a large magnetocaloric effect, whose largest -ΔS _m value is 21.88 J kg^-1 K^-1 (when T = 2 K and ΔH = 5 T); it thus can be utilized as a good magnetic refrigeration molecular material.

Terminal Ligand and Packing Effects on Slow Relaxation in an Isostructural Set of [Dy(H2 dapp)X2 ]+ Single Molecule Magnets*

We report three structurally related single ion Dy compounds using the pentadentate ligand 2,6-bis((E)-1-(2-(pyridin-2-yl)-hydrazineylidene)ethyl)pyridine (H2 dapp) [Dy(H2 dapp)(NO3 )2 ]NO3 (1), [Dy(H2 dapp)(OAc)2 ]Cl (2) and [Dy(H2 dapp)(NO3 )2 ]Cl0.92 (NO3 )0.08 (3). The (H2 dapp) occupies a helical twisted pentagonal equatorial arrangement with two anionic ligands in the axial positions. Further influence on the electronic and magnetic structure is provided by a closely associated counterion interacting with the central N-H group of the (H2 dapp). The slow relaxation of the magnetisation shows that the anionic acetates give the greatest slowing down of the magnetisation reversal. Further influence on the relaxation properties of compounds1 and 2 is the presence of short nitrate-nitrate intermolecular ligand contact opening further lattice relaxation pathways.

Assembly of chiral 3d–4f wheel-like cluster complexes with achiral ligands: single-molecule magnetic behavior and magnetocaloric effect

With the help of perchlorate ions, chiral M₃Ln₃ wheel-like cluster complexes were constructed from achiral ligands, and showed single-molecule magnetic behavior and magnetocaloric effect.

Zn2Ln2 complexes with carbonate bridges formed by the fixation of carbon dioxide in the atmosphere: single-molecule magnet behaviour and magnetocaloric effect

In the self-assembly process, CO₂ in the air is automatically fixed to Zn₂Ln₂ cluster molecular materials.

Dehydration-Hydration Switching of Single-Molecule Magnet Behavior and Visible Photoluminescence in a Cyanido-Bridged DyIIICoIII Framework

Microporous magnets compose a class of multifunctional molecule-based materials where desolvation-driven structural transformation leads to the switching of magnetic properties. Herein, we present a special type of microporous magnet where a dehydration-hydration process within a bimetal coordination framework results in the switching of emissive Dy^III single-molecule magnets (SMMs). We report a three-dimensional (3-D) cyanido-bridged coordination polymer, {[Dy^III(H₂O)₂][Co^III(CN)₆]}·2.2H₂O (1), and its dehydrated form of {Dy^III[Co^III(CN)₆]} (2), which was obtained through a reversible single-crystal-to-single-crystal transformation. Both phases are composed of paramagnetic Dy^III centers alternately arranged with diamagnetic hexacyanidocobaltates(III). The hydrated phase contains eight-coordinated [Dy^III(μ-NC)₆(H₂O)₂]^3- complexes of a square antiprism geometry, while the dehydrated form contains six-coordinated [Dy^III(μ-NC)₆]^3- moieties of a trigonal prism geometry. This change in coordination geometry results in the generation of Dy^III single-molecule magnets in 2, whereas slow magnetic relaxation effect is not observed for Dy^III sites in 1. The D_4d-to-D_3h symmetry change of Dy^III complexes produces also the shift of photoluminescent color from nearly white to deep yellow thanks to the modulation of emission bands of f-f electronic transitions. A combined approach utilizing dc magnetic data and low-temperature emission spectra confirmed an axial crystal field of trigonal prismatic Dy^III complexes in 2, which produces an Orbach type of slow magnetic relaxation. Therefore, we present a unique route to the efficient switching of SMM behavior and photoluminescence of Dy^III complexes embedded in a 3-D cyanido-bridged framework.

Microwave-assisted synthesis: from a mononuclear {CoII} complex to {CoII9} solvomorphs

Microwave-assisted control over nuclearity and solvomorphism.

Both magnetic relaxation and luminescence of Zn2Dy2 cluster complexes regulated by the bis-imine chain in Schiff base ligands

The bis-imine bridge in Schiff base ligands has effects on the magnetic relaxation and luminescence of two Zn₂Dy₂ cluster complexes.

Arraying Octahedral {Cr2Dy4} Units into 3D Single-Molecule-Magnet-Like Inorganic Compounds with Sulfate Bridges

Two novel 3D pure inorganic compounds based on [Cr₂Dy₄(μ₄-O)₂(μ₃-OH)₄]¹⁰⁺ cluster units and sulfate anions are presented. Both complexes exhibit single-molecule-magnet (SMM)-like behavior. Permutation of the magnetic moment direction among SMM-like cluster units has a significant effect on the performance of molecular nanomagnets, and directional consistency shows obvious advantages.