Rationally Designing Metal–Organic Frameworks Based on [Ln₂] Magnetic Building Blocks Utilizing 2-Hydroxyisophthalate and Fine-Tuning the Magnetic Properties of Dy Analogues by Terminal Coordinated Solvents

Abstract

By utilizing the 2-hydroxyisophthalic acid (H 3 ipO) ligand, 2D metal−organic frameworks (MOFs) featuring rare O phenol -bridged [Ln 2 ]magnetic building blocks (MBBs), [Ln 2 (ipO) 2 (DMF)(H 2 O)] [Ln = Gd (1), Dy (2); DMF = N,N-dimethylformamide], were rationally designed and synthesized. When the reaction solvents that behave as terminal ligands were changed, the coordination geometries of Ln III ions and the arrangement fashion of [Ln 2 ]-MBBs for these MOFs were modified accordingly. Another 3), Dy (4)] was thus obtained. MOFs 1 and 3 exhibited favorable magnetocaloric effect, whose maximum −ΔS m values reach 30.0 and 31.7 J kg −1 K −1 , respectively. None of the single-molecule-magnet (SMM) behavior was observed in 2. However, from 2 to 4, the change of the terminal coordinated solvents brought obvious improvement of the magnetic properties. MOF 4 showed interesting relaxation behavior, in which dual relaxation was only visible under weak direct-current fields, and its highest effective energy barrier (U eff ) reached up to 243 K. Ab initio calculations revealed the tuning mechanism of the terminal coordinated solvents. Their change optimized the arrangements of the magnetic axis of the Dy III centers in both each MBB and the whole framework, thus improving the magnetic anisotropy and magnetic interactions of the system. Significantly, within the [Dy 2 ]-MBBs of 4, the angle made by the individual magnetic axis and Dy•••Dy′ line is nearly 0°. This case favoring a high SMM performance not only was scarcely achieved in discrete {Ln 2 }-SMMs with numerous members but also has never been observed in any MBB-based MOFs as far as we know.

Soft Metal–Organic Frameworks Based on {Na@Ln6} as a Secondary Building Unit Featuring a Magnetocaloric Effect and Fluorescent Sensing for Cyclohexane and Fe3+

“…In order to obtain multifunctional Ln-MOFs, an effective design and synthetic strategy are essential. Investigations on the reported research found that it was an effective method to construct cluster-based MOFs by using metal clusters as second building units (SBUs) under the condition of the multidentate chelating ligands controlling hydrolysis. − Lanthanide ions tend to coordinate with O based on the hard–soft-acid–base (HASB), so the flexible polycarboxylic and polyalcohol ligands may be the best candidates. Considering the above factors, we have chosen the flexible and cheap ethylene diamine tetraacetic acid (H 4 EDTA) as the multidentate chelating ligand and prepared two series of cluster-based Ln-MOFs with formulas {[Na@Ln 8 (EDTA) 6 ­(H 2 O) 22 ]­·ClO 4 · x H 2 O} n ( x ≈ 28, Ln = Gd for 1 , Ln = Eu for 2 ) and {[Na@Ln 9 (EDTA) 6 ­(H 2 O) 27 ]­·(ClO 4 ) 4 · x H 2 O} n ( x ≈ 26, Ln = Gd for 3 , Ln = Eu for 4 ) by controlling the hydrolysis of different lanthanide ions.…”

Stable Lanthanide Metal–Organic Frameworks with Ratiometric Fluorescence Sensing for Amino Acids and Tunable Proton Conduction and Magnetic Properties

“…The maximum values of M are 6.51 Nβ for 2 , 5.18 Nβ for 3 , and 6.55 Nβ for 4 at 70 kOe (Figure S27, SI). These values of 3 and 4 are much lower than the saturation value, which may be due to the large magnetic anisotropy and/or low excited state of Tb III and Dy III ions. , …”

“…These values of 3 and 4 are much lower than the saturation value, which may be due to the large magnetic anisotropy and/or low excited state of Tb III and Dy III ions. 59,60 Considering the weak magnetic coupling between isotropic Gd III ions, we also investigated the magnetocaloric properties of 2 (Figure S28, Supporting Information). According to the experimental data, the magnetic entropy change (−ΔS m ) can be calculated through the Maxwell equation ΔS m (T) ΔH = ∫ [∂M(T, H)/∂T] H dH.…”

Two Series of Tetranuclear Ln(III)-Based Clusters: Structures, Magnetic Behaviors, and Efficient Cycloaddition of CO2 to Oxazolidinones

“…On the other hand, profiting from negligible magnetic anisotropy, a high magnetic density, and a large spin ground state, the Gd­(III) ion is proposed to construct polynuclear clusters, which is considered a promising candidate for magnetic refrigerating materials due to more energy-efficient and environmentally friendly than other traditional refrigerants. − Another fascinating species in the magnetic field Dy­(III) ion with a large intrinsic anisotropy and huge ground-state spin, which is an advantageous platform for constructing single-molecule-magnet (SMM). − Rationally modifying the coordination environment of the Ln­(III) centers through perturbing the magnetic interactions to improve the magnetic performance has attracted numerous attention. − It is worth noting that simultaneously regulating two components to construct a series of polynuclear lanthanide clusters with significant magnetic behaviors has barely been reported.…”