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Three new Ln4 clusters based on a bidentate Schiff base ligand having formulae [Ln4(μ3-OH)2L6(acac)4]·xCH3CN (Ln(iii) = Eu(1), Gd(2) and Dy(3), x = 1 for 1, x = 2 for 2, and x = 0 for 3, HL = 5-(4-o-hydroxybenzylidene)-8-hydroxylquinoline and acac = acetylacetone) have been successfully synthesized and completely characterized. The structures of 1–3 are similar to each other except for the nature of the central ion and the number of free acetonitrile molecules. The four LnIII ions are coplanar and clusters 1–3 have a butterfly-shaped arrangement. Magnetic studies show that cluster 2 displays a weak antiferromagnetic exchange interaction between nearby GdIII centers and exhibits magnetic refrigeration with maximum −ΔSm = 18.85 J kg−1 K−1 (ΔH = 7.0 T at 2.5 K). Alternating current (ac) magnetic susceptibility measurement of 3 indicates that 3 demonstrates SMMs behavior under a zero direct-current (dc) field, with an effective energy barrier (ΔE/kB) of 79.15 K and a pre-exponential factor τ0 = 5.82 × 10−8 s. [ABSTRACT FROM AUTHOR]

Two cationic heterometal–organic frameworks (Eu-Zn (1·NO3−) and Tb-Zn (2·NO3−)) with NO3− counter-anions in the channels are structurally and luminously characterized. Both of them can serve as highly sensitive and highly selective luminescent probes for detecting I− ions in aqueous solutions. In particular, 2·NO3− can selectively and reversibly detect I− with a fast response time of just 10 s and an extremely low detection limit of 0.001 ppm. Mechanism studies reveal that I− is quickly oxidized to form I3− with the help of 1·NO3− or 2·NO3−, leading to luminescence quenching. This represents the first report of MOF-based luminescent probes for the detection of I− in aqueous solutions. [ABSTRACT FROM AUTHOR]

Two unique 3D coordination polymers based on octahedral [Ln6] (Ln = Gd (1), Dy (2)) clusters as nodes were synthesized, exhibiting a novel (3,12)-connected topology with the symbol of (420·626·820)(43)4. The magnetic studies reveal that 1 shows a −ΔSm = 46.6 J kg−1 K−1, falling among the largest values known to date, and 2 displays slow magnetic relaxation behavior. Both 1 and 2 have high thermal and solvent stabilities. [ABSTRACT FROM AUTHOR]

Two novel Dy–Cu MOFs were structurally and magnetically characterized. The results reveal that it is the first example of anion-induced change of structure interpenetration and magnetic properties in 3d–4f MOFs. [ABSTRACT FROM AUTHOR]

Two cationic heterometal-organic frameworks (Eu-Zn (1·NO₃⁻) and Tb-Zn (2·NO₃⁻)) with NO3(-) counter-anions in the channels are structurally and luminously characterized. Both of them can serve as highly sensitive and highly selective luminescent probes for detecting I(-) ions in aqueous solutions. In particular, 2·NO₃⁻ can selectively and reversibly detect I(-) with a fast response time of just 10 s and an extremely low detection limit of 0.001 ppm. Mechanism studies reveal that I(-) is quickly oxidized to form I₃⁻with the help of 1·NO₃⁻ or 2·NO₃⁻, leading to luminescence quenching. This represents the first report of MOF-based luminescent probes for the detection of I(-) in aqueous solutions.

Two unique heptanuclear clusters Ln@Zn6 (Ln = Dy (1), Er (2)) were structurally and magnetically characterized. Each Dy(3+)/Er(3+) is located in a nona-coordinate D(3h) coordination environment, and is encapsulated in a diamagnetic Zn6 cage. Compound 1 exhibits single-ion magnetic behavior, and is the first example of a single-ion magnet (SIM) constructed through embedding one magnetic anisotropic metal ion into a diamagnetic cage.

Eight three-dimensional lanthanide-organic frameworks: [Ln(BPDC)1.5(DMF)(H2O)2]·2H2O (Ln = Eu (1), Gd (2), Tb (3), Dy (4); BPDC = 4,4'-dicarboxylate-2,2'-dipyridine anion), [Ln(BPDC)(DMF)2(NO3)] (Ln = Eu (5), Gd (6), Tb (7), Dy (8)) were fabricated and structurally characterized. Compounds 1-4 are isostructural, belonging to the triclinic system with space group P1¯, while compounds 6-8 belong to the monoclinic system with space group C2/c. Structural differences between two types of compounds may be caused by different reaction conditions. Magnetic properties of 2-4 and 6-8 have been investigated and only compounds 4 and 8 display significant frequency-dependence, albeit without reaching the characteristic maxima above 2 K, implying slow magnetic relaxation behaviors in 4 and 8. After the application of a DC field, good peak shapes of AC signal were obtained and got the energy barrier for 4, ΔE/kB = 79.80 K and the pre-exponential factor τ0 = 1.28 × 10(-10) s, for 8, ΔE/kB = 38.15 K and τ0 = 2.47 × 10(-9) s. Geometrical differences in the crystal fields of Dy(3+) in 4 and 8 seem to be responsible for the large divergence of their magnetic behaviors. Luminescence analyses were performed on coordination polymers containing Eu(3+), Tb(3+), and Dy(3+), which exhibit the characteristic transitions of corresponding lanthanide ions, and give the lifetime (τ0) of 1, 3, 4, 5, 7 and 8 are 0.56 ms, 0.89 ms, 8.48 μs, 0.60 ms, 0.75 ms and 36.35 μs, respectively.

Five novel compounds {[Cu(CMA)]·0.8H(2)O}(n) (1), {[Cu(CMA)(bpy)(0.5)]·0.5DMF}(n) (2), {[Cu(CMA)(bpy)(H(2)O)]·0.5H(2)O}(n) (3), {[Cu(2)(CMA)(DPA)(bpy)(2)(H(2)O)]ClO(4)}(n) (4) and {[Cu(3)(CMA)(DPA)(bpy)(4)(OH)](ClO(4))(2)·3H(2)O)}(n) (5) (H(2)CMA = 3-(carboxymethoxy)-5-methylbenzoic acid, HDPA = 2-(3,5-dimethylphenoxy)acetic acid, bpy = 4,4'-bipyridine) were synthesized and characterized by single crystal X-ray diffraction. Interestingly, the kinds of ligands included in these compounds are different: 1 contains single-ligand CMA(2-); 2 and 3 comprise two kinds of ligands (CMA(2-) and bpy); 4 and 5 cover three kinds of ligands (CMA(2-), DPA(-) and bpy). Structural analyses reveal that 1-3, and 5 are three-dimensional (3D) frameworks, while 4 is a 2D layer. Noteworthily, 1 possesses two types of channels: six-star and hexagonal ones. 3 displays a three-fold interpenetrating 3D framework. The structural diversity of the compounds may have originated from different anions, solvents and temperatures. Variable-temperature magnetic susceptibility measurements were carried out on compounds 1, 2 and 4, and the magnetic properties are dramatically different due to the structural diversities. The magnetic data of 1 shows an antiferromagnetic interaction with J = -54.84 cm(-1) estimated from the Bonner-Fisher model. The magnetic data of 2 was least-square fitted to the Blenaey-Bowers equation with J = -131.01 cm(-1), indicating the existence of a strong antiferromagnetic interaction between two adjacent Cu(2+). The magnetic data of linear tetranuclear structure 4 was best fitted to the expression derived from the Hamiltonian H = -2(2J(1)S(1)S(2) + J(2)S(1)S(1*)). The best fitting parameters are J(1) = -17.48 cm(-1) and J(2) = -65.26 cm(-1), which also indicate an antiferromagnetic interaction. Simultaneously, the magneto-structural relationship was discussed.

We present one 3D cationic MOF (1-ClO(4)), which exhibits high thermal stability and strong alkali resistance. More importantly, it displays fast, selective capture of, and acts as a luminescent probe for, pollutant CrO(4)(2-) by anion exchange. Additionally, 1-ClO(4) exhibits interesting slow magnetic relaxation behavior at low temperature.

Seven lanthanide-cobalt heterometallic three-dimensional coordination polymers: {[Ln(3)Co(2)(BPDC)(5)(HBPDC)(H(2)O)(5)](ClO(4))(2)·mH(2)O}(n) (Ln = Eu (1, m = 10.25), Gd (2, m = 8), Tb (3, m = 9.5), Dy (4, m = 11), Ho (5, m = 10.5), Tm (6, m = 11), Lu (7, m = 10.25); BPDC = 5,5'-dicarboxylate-2,2'-dipyridine anion) were structurally and magnetically characterized. Compounds 1-7 crystallize in the orthorhombic space group Pbca, featuring a 3D sandwich framework. Magnetic properties of 2-6 have been investigated by using DC (direct current) and AC (alternating current) susceptibility measurements. Among these compounds, only compound 4 displays significant frequency dependence, albeit without reaching the characteristic maxima above 2 K, implying slow magnetic relaxation behavior in 4. After the application of a DC field, good peak shapes of AC signals were obtained and the energy barrier ΔE/k(B) = 62.89 K and the preexponential factor τ(0) = 6.16 × 10(-8) s. To our knowledge, 4 has the highest energy barrier in Ln-Co SMM systems hitherto.