Syntheses, structures, and magnetic properties of acetate-bridged lanthanide complexes based on a tripodal oxygen ligand

Four homodinuclear lanthanide complexes, Dy2 (LOEt)2(OAc)4 (1), Tb2 (LOEt)2(OAc)4 (2), Ho2(LOEt)2(OAc)4 (3), and Gd2 (LOEt)2(OAc)4 (4), have been synthesized and characterized based on a tripodal oxygen ligand Na [(η5-C5H5)Co(P(O)(OC2H5)2)3] (NaLOEt). Structural analyses show that the acetate anions bridge two symmetry-related Ln3+ ions in the μ2:η1:η1 and μ2:η1:η2 coordination patterns, and each lanthanide (III) ion owns a twisted square antiprism (SAPR) conformation. Static magnetic measurements reveal the weak intramolecular ferromagnetic interaction between dysprosium (III) ions in 1 and antiferromagnetic Ln3+···Ln3+ couplings in the other three complexes. Through the analysis of the ligand-field effect and magnetic anisotropy axis orientation, the reasons for the lack of dynamic magnetic behavior in 1 were identified.

Macrocycle supported dinuclear lanthanide complexes with different β-diketonate co-ligands displaying zero field single-molecule magnetic behaviour

Three different sets of isomorphous dinuclear Gd/Dy complexes with an uncommon macrocyclic ligand and β-diketonate co-ligands were reported in which Dy2 analogues are zero field SMMs.

A dye encapsulated zinc-based metal-organic framework as a dual-emission sensor for highly sensitive detection of antibiotics

Self-assembly of two Zn-MOFs, [Zn₂L(DMF)₃]·H₂O·5DMF (1) and [Zn₂L(H₂O)₂]·4H₂O·3DMF (2), was achieved with an amide-functionalized tetracarboxylate ligand under similar conditions. Incorporated amide groups make the tetratopic linkers exhibit different configurations, tetrahedron and square, and subsequently combine tetrahedral [Zn₂(CO₂)₄] clusters or square paddle-well [Zn₂(CO₂)₄] clusters to afford a lon net for 1 and a nbo net for 2. Remarkably, 2 demonstrated high porosity and amide group decorated cages, and thereby proved to be a good capturing agent for a fluorescent dye molecule (DMASM). Consequently, a dual-emitting DMASM@2 sensor was successfully fabricated based on effective energy transfer from the host framework to DMASM with the variable luminescent color being visible to the naked eye. DMASM@2 could be used for the detection of metronidazole (MDZ) and dimetridazole (DTZ) with high sensitivity and remarkable recyclability.

Successive syntheses and magnetic properties of homodinuclear lanthanide macrocyclic complexes

A series of homodinuclear β-diketone lanthanide(III) complexes, formulated as [(acac)₄Ln₂(L1)] (Ln³⁺ = Dy³⁺ (1), Tb³⁺ (2), and Gd³⁺ (3), respectively) were first synthesized based on a closed-macrocyclic ligand (H₂L1) derived from the [2 + 2] cyclocondensation of 4-tert-butyl-2,6-diformylphenol and o-phenylenediamine in the presence of lanthanide acetylacetonates. Subsequently, by using the above compounds as building blocks to assemble directly with another Schiff base ligand, N,N'-bis(5-chlorosalicylidene)-o-phenylenediamine (H₂L2), three new homodinuclear sandwich-type lanthanide complexes with the general formula [Ln₂(L1)(L2)₂] (Ln³⁺ = Dy³⁺ (4), Tb³⁺ (5), and Gd³⁺ (6), respectively) were further designed and prepared. Single-crystal X-ray analyses show that the central Ln³⁺ ion adopts a distorted square antiprism conformation with D_4d local symmetry. Magnetic studies reveal ferromagnetic interaction between Dy³⁺ and Tb³⁺ centres and zero-field slow relaxation of magnetization for Dy complexes 1 and 4. The corresponding magneto-structural correlations of SMMs 1 and 4 were further discussed by theoretical calculations and with experimental outcomes.

Macrocycle supported dimetallic lanthanide complexes with slow magnetic relaxation in Dy2 analogues

Six dimetallic lanthanide complexes, [Ln2(L')(acac)4] (1Dy-3Gd) (Ln = Dy (1Dy), Tb (2Tb) and Gd (3Gd)) and [Ln2(L')(tfac)4] (4Dy-6Gd) (Ln = Dy (4Dy), Tb (5Tb) and Gd (6Gd)) (H2L' = 1,9-dichloro-3,7,11,15-tetraaza-1,9(1,3)-dibenzenacyclohexadecaphane-2,10-diene-1,9-diol), have been synthesized by the reaction of lanthanide nitrates with the HL ligand in the presence of acetylacetonate (acac) (or trifluoroacetylacetonate (tfac) and triethylamine (HL = 4-chloro-2,6-bis(-((3-((3-(dimethylamino)propyl)amino)propyl)imino)methyl)phenol). Ln-Assisted modification of the Schiff base HL occurred and led to the formation of a new macrocyclic ligand (H2L'). X-ray crystallographic analysis revealed that the LnIII ions of complexes 1Dy-6Gd are all eight-coordinated in a square antiprismatic geometry with D4d local symmetry. Magnetic measurements of these complexes revealed that 1Dy and 4Dy show single-molecule magnet behaviour with energy barriers of 66.7 and 79.0 K, respectively, under a zero direct magnetic field. The orientations of the magnetic axes and crystal field parameters were obtained from theoretical calculations and an electrostatic model. The magneto-structural correlations of SMMs 1Dy and 4Dy are further discussed in detail.

Insight into the Construction of (3,6)-Connected rtl, ant, and Chiral anh Nets Based on Structural Investigation of Several MOFs via Steric Tuning of Linkers

Six cobalt-organic frameworks (1-6) were solvothermally constructed with a tritopic pyridine-carboxylate linker (L-H) and its methyl- and methoxy-functionalized derivatives (L-OCH₃ and L-CH₃). Due to incorporated multiple substituents with various steric hindrances, the tritopic linkers adopt different molecular configurations, Y-shaped and T-shaped, which further combine octahedral or trigonal-prismatic inorganic nodes to afford diverse (3,6)-connected nets. Consequently, 1 and 2 are rtl nets and 3 and 4 are ant nets. Notably, 5 and 6 present rarely observed chiral anh (flu-3) networks with left-handed double helical chains. The structural investigation indicates that the steric tuning of linkers may essentially dictate the resulting diverse MOF structures. Furthermore, the MOFs presented here can be regarded as an ideal structural platform for a better understanding of the assembly of (3,6)-connected rtl, ant, and chiral anh nets, which are closely related to the shape and geometric configuration/conformation of tridentate organic nodes as well as inorganic building nodes.