The Complete Series of Lanthanoid-Chloranilato Lattices with Dimethylsulfoxide: Role of the Lanthanoid Size on the Coordination Number and Crystal Structure

Anilato-Based Coordination Polymers with Slow Relaxation of the Magnetization: Role of the Synthetic Method and Anilato Ligand

We have prepared and characterized three coordination polymers formulated as [Dy2(C6O4Cl2)3(fma)6] ⋅ 4.5fma (1) and [Dy2(C6O4X2)3(fma)6] ⋅ 4fma ⋅ 2H2O with X=Br (2) and Cl (3), where fma=formamide and C6O4X2 2-=3,6-disubstituted-2,5-dihydroxy-1,4-benzoquinone dianion with X=Cl (chloranilato) and Br (bromanilato). Compounds 1 and 3 are solvates obtained with slow and fast precipitation methods, respectively. Compounds 2 and 3 are isostructural and only differ in the X group of the anilato ligand. The three compounds present (6,3)-gon two-dimensional hexagonal honey-comb structures. Magnetic measurements indicate that the three compounds show slow relaxation of the magnetization at low temperatures when a continuous magnetic field is applied, although with different relaxation times and energy barriers depending on X and the crystallisation molecules. Compounds 1-3 represent the first examples of anilato-based lattices with formamide and field-induced slow relaxation of the magnetization.

The Versatility of Ethylene Glycol to Tune the Dimensionality and Magnetic Properties in DyIII-Anilato-Based Single-Ion Magnets

We exploit the high versatility of the solvent ethylene glycol (eg = CH₂OH-CH₂OH) acting as a ligand with three different coordination modes: terminal (κO), chelate (κ²O,O'), and bridge (1κO,2κO') to prepare a novel family of six different coordination polymers with Dy^III and three different anilato ligands (3,6-disubstituted-2,5-dihydroxy-1,4-benzoquinone dianion = C₆O₄X₂^2-, with X = H, Cl, and Br). With the X = H derivative (dhbq^2-), we have prepared [Dy₂(dhbq)₃(eg)₂(μ-eg)]·4eg·2H₂O (1), a 3D diamond-like network with a chelate and bridging eg molecules. With the X = Cl derivative (chloranilato), we have prepared [Dy₂(C₆O₄Cl₂)₃(eg)₄]·2eg·H₂O (2) and [Dy₂(C₆O₄Cl₂)₃(μ-eg)(H₂O)₄]·2eg·7H₂O (3). Compound 2 has a 2D (6,3)-gon brick-wall lattice and contains a chelate and a terminal eg molecule. Compound 3 has a 3D diamond-like topology as 1, although now the chelate eg has been replaced by two water molecules. Finally, with the X = Br derivative (bromanilato), we have obtained [Dy₂(C₆O₄Br₂)₃(eg)₂(CH₃OH)₂]·2eg·4CH₃OH (4), [Dy₂(C₆O₄Br₂)₃(eg)₄]·4eg (5), and [Dy₂(C₆O₄Br₂)₃(eg)₃(H₂O)]·2eg·H₂O (6). Compound 4 has a 2D (6,3)-gon herringbone topology and contains a chelate eg and a MeOH molecule. Compounds 5 and 6 have a 2D (6,3)-gon brick-wall topology with a chelate and a terminal eg molecules (in 5 and in one of the two independent Dy centers of 6). The other Dy center in 6 has a chelate eg and a water molecule. All the compounds show slow relaxation of the magnetization at low temperatures (in compounds 1, 2, and 5 with no applied DC field). The magnetization of compounds 1-6 relaxes through Orbach and direct mechanisms when a DC field is applied and through an Orbach and/or quantum tunneling mechanism when no DC field is applied.

Metal-Organic Framework vs. Coordination Polymer—Influence of the Lanthanide on the Nature of the Heteroleptic Anilate/Terephtalate 3D Network

Metal-organic frameworks (MOFs), whose definition has been regularly debated, are a sub-class of coordination polymers (CPs) which may feature both an overall 3D architecture and some degree of porosity. In this context, MOFs based on lanthanides (Ln-MOFs) could find many applications due to the combination of sorption properties and magnetic/luminescent behaviors. Here we report rare examples of 3D Ln-CPs based on anilate linkers, obtained under solvothermal conditions using a heteroleptic strategy. The three compounds of formula [Yb2(μ-ClCNAn)2(μ-F4BDC)(H2O)4]·(H2O)3 (1), [Er2(μ-ClCNAn)2(μ-F4BDC)(H2O)4]·(H2O)4 (2) and [Eu2(μ-ClCNAn)2(μ-F4BDC)(H2O)6] (3) have been characterized by single-crystal X-ray diffraction, thermogravimetric analysis, and optical measurements. Structural characterization revealed that compounds 1 and 2 present an interesting MOF architecture with extended rectangular cavities which are only filled with water molecules. On the other hand, compound 3 shows a much more complex topology with no apparent cavities. We discuss here the origins of such differences and highlight the crucial role of the Ln(III) ion nature for the topology of the CP. Compounds 1 and 2 now offer a playground to investigate the possible synergy between gas/solvent sorption and magnetic/luminescent properties of Ln-MOFs.