Intramolecular ferro- and antiferromagnetic interactions in oxo-carboxylate bridged digadolinium(iii) complexes

Ferrocenyl-based di- and trinuclear lanthanide complexes: solid state structures, (spectro)electrochemical and DFT studies

Dinuclear and trinuclear ferrocenylcarboxylato-bridged lanthanide complexes of type [Ln(μO:κ2OO'-O2CFc)(O2CFc)2(H2O)(dmf)]2·(dmf)2 (Ln = Sm (2), Eu (3), Gd (4), Tb (5); Fc = Fe(η5-C5H4)(η5-C5H5)), and novel [Bu4N][Ln3(μ-O2CFc)3(μO:κ2OO'-O2CFc)3(O2CFc)3(μ3-OH)]·[Bu4N]Cl (Ln = Gd (6), Tb (7)) were prepared by the reaction of [LnCl3·6H2O] (synthesis of 2-5) or LnCl3 (synthesis of 6, 7) with FcCO2H (1) in the ratio of 1 : 3. As evidenced by single crystal X-ray structure determination, in 2-5 the lanthanide ions are connected by symmetric FcCO2 units. In addition, two ferrocenylcarboxylato groups are μ-bridged to LnIII. Each LnIII ion is coordinated by nine oxygen donor atoms derived from one H2O, one dmf and three carboxylates. The latter are found in chelating κ2 and bridging μ,κ3 coordination modes. Complexes 6 and 7 assemble three LnIII cores around a central μ3-netting hydroxide and nine FcCO2 entities. A combination of κ2, μ,κ2 and μ,κ3 coordination modes results in an eight-fold coordination sphere for each metal, which is best described as bicapped trigonal prismatic. IR spectroscopy confirms the chelating and bridging motifs. Electrochemical studies of complexes 2-7via cyclic voltammetry (CV) and square-wave voltammetry (SWV) showed one redox event between E°' = 250 and 260 mV vs. FcH/FcH+ for 2-5 with all six FcCO2 redox events superimposed. Complexes 6 and 7 show a total of three events in the CV with the oxidations of the nine FcCO2 units occurring in close proximity. Deconvolution of individual redox events correlates well with the mononuclear complex [Bu4N][Gd(O2CFc)4]. UV-Vis/NIR spectroelectrochemical measurements of 7 did not reveal electron transfer between either Fc units, nor the coordinated lanthanides and resembled the absorption behavior of [Bu4N][Tb(O2CFc)4]. DFT (Density Functional Theory) calculations on the B3LYP def2-TZVP level of theory were carried out to assign the order of redox events in 6 showing that the spatial distance towards the most recent redox center, instead of the binding mode, is decisive.

Highly luminescent mixed-ligand bimetallic lanthanoid(III) complexes for photovoltaic applications

Six new mixed-ligand bimetallic complexes [Eu₂(bz)₄(tta)₂(phen)₂] (1), [Gd₂(bz)₄(tta)₂(phen)₂] (2), [EuTb(bz)₄(tta)₂(phen)₂] (3), [EuGd(bz)₄(tta)₂(phen)₂] (4), [Eu_1,2Gd_0,8(bz)₄(tta)₂(phen)₂] (5) and [Eu_1,6Gd_0,4(bz)₄(tta)₂(phen)₂] (6) have been prepared with the Eu³⁺, Gd³⁺ and Tb³⁺ ions and the benzoate (bz^-), 2-thenoyltrifluoroacetonate (tta^-) and the 1,10-phenanthroline (phen) ligands. The compounds combine highly efficient antennas to obtain highly luminescent complexes to enhance solar cell efficiency. The benzoate ligand has been chosen to take its advantage as a bridging ligand to end up with bimetallic complexes to study the effect of combining two metal ions in the luminescent molecule. The structure of 1 was obtained by single-crystal X-ray diffraction, and 1-6 were found to be isostructural by powder X-ray diffraction analysis. The photophysical properties were studied by the absorbance and emission spectra and emission lifetimes. The magnetic properties of 2 were studied, and we found intramolecular antiferromagnetic interactions between the Gd³⁺ ions. We prepared luminescent down-shifting layers (LDSL) with the 1, 3-6 complexes embedded in ethylene-vinyl-acetate and studied their effect in the external quantum efficiency (EQE) and intensity-voltage (I-V) plots of a solar mini-module. We found that LDSL containing the bimetallic complexes 3 and 6 enhance the efficiency of the solar mini-module from 11.26(3)% to 11.76(4)% (+0.52%) and to 11.44(2)% (+0.21%), respectively.

Heterometallic Octanuclear NiII 4LnIII 4 (Ln = Y, Gd, Tb, Dy, Ho, Er) Complexes Containing NiII 2LnIII 2O4 Distorted Cubane Motifs: Synthesis, Structure, and Magnetic Properties

The reaction of 2-methoxy-6-[{2-(2-hydroxyethylamino)ethylimino}methyl] phenol (LH₃) with lanthanide metal salts followed by the addition of nickel acetate allowed isolation of a family of octanuclear complexes, [Ni₄Ln₄(μ₂-OH)₂(μ₃-OH)₄(μ-OOCCH₃)₈(LH₂)₄]·(OH)₂·xH₂O. Single crystal X-ray diffraction studies of these complexes reveal that their central metallic core consists of two tetranuclear [Ni₂Ln₂O₄] cubane subunits fused together by acetate and hydroxide bridges. The magnetic study of these complexes reveals a ferromagnetic interaction between the Ln^III and the Ni^II center. The magnitude of exchange coupling between the Ni^II and Ln^III center, parametrized from the magnetic data of the Gd analogue, gives J = +0.86 cm^-1. The magneto caloric effect, studied for the Ni^II ₄Gd^III ₄ complex, shows a maximum of magnetic entropy change, -ΔS _m = 22.58 J kg^-1 K^-1 at 3 K for an applied external field of 5 T.

Coming full circle: constructing a [Gd6] wheel dimer by dimer and the importance of spin topology

Conversion of dimer → linear tetramer → cyclic hexamer reveals remarkable topological size effects.

Mononuclear and polynuclear complexes ligated by an iminodiacetic acid derivative: synthesis, structure, solution studies and magnetic properties

Two novel families of coordination polymers, [Ln(bzlida)(Hbzlida)]·H₂O (Ln = La, Nd) and [Ln₂(bzlida)₃]·3H₂O (Ln = Nd, Sm, Eu, Gd) were prepared by hydrothermal reaction of Ln₂O₃ with benzyliminodiacetic acid.

Syntheses, structures, and magnetic properties of homodinuclear lanthanide complexes based on dinucleating Schiff base ligands

Two series of homodinuclear lanthanide(iii) complexes were synthesized and characterized. Magnetic studies reveal the weakly antiferromagnetic coupling between paramagnetic Ln ions and enhanced relaxation of magnetization for Dy₂ complexes.

Enhancing luminescence properties of lanthanide(iii)/pyrimidine-4,6-dicarboxylato system by solvent-free approach

Solvent-free reaction between lanthanide nitrates and pyrimidine-4,6-dicarboxylic acid led to 3D frameworks with coordinated nitrates showing a photoluminescence improvement and waveguiding behaviour.

Three sra topological lanthanide–organic frameworks built from 2,2′-dimethoxy-4,4′-biphenyldicarboxylic acid

The first neutral 3D sra-LOF built from a 1D inorganic rod-shaped chain [Ln(CO₂)₂(HCO₂)]_n (Ln = Eu, Gd, Dy) was synthesized.

Poly[tetra-aqua-(5-hy-droxy-pyridin-1-ium-3-carboxyl-ato-κO (3))tris-(μ-oxalato-κ(4) O (1),O (2):O (1'),O (2'))dieuropium(III)]

In the title compound, [Eu₂(C₆H₅NO₃)₂(C₂O₄)₃(H₂O)₄]_n, the Eu^III atom is bonded to one O atom from a monodentate 5-hy­droxy­pyridin-1-ium-3-carboxyl­ate ligand, six O atoms from three oxalate ligands and two water mol­ecules, exhibiting a highly distorted tricapped trigonal geometry. Three independent oxalate ligands, each lying on an inversion center, bridge the Eu^III atoms, forming a brickwall-like layer parallel to (001), which is stabilized by intra­layer O—H⋯O hydrogen bonds. The layers are further linked through inter­layer O—H⋯O and N—H⋯O hydrogen bonds and π–π inter­actions between the pyridine rings [centroid–centroid distance = 3.5741 (14) Å] into a three-dimensional supra­molecular network.

Diversity of lanthanide(III)-2,5-dihydroxy-1,4-benzenedicarboxylate extended frameworks: syntheses, structures, and magnetic properties

Six lanthanide(III)-2,5-dihydroxy-1,4-benzenedicarboxylate frameworks, namely, [Ln(H(2)-DHBDC)(1.5)(H(2)O)(2)](n) (Ln = La (1) and Pr (2); H(4)-DHBDC = 2,5-dihydroxy-1,4-benzenedicarboxylic acid), {[Nd(H(2)-DHBDC)(1.5)(H(2)O)(3)](H(2)O)}(n) (3), {[Eu(H(2)-DHBDC)(NO(3))(H(2)O)(4)](H(2)O)(2)}(n) (4), and {[Ln(2)(H(2)-DHBDC)(2)(DHBDC)(0.5)(H(2)O)(3)](H(2)O)(4)}(n) (Ln = Gd (5) and Dy (6)), with four different structural types ranging from 1D chain, 2D layer to 3D networks have been synthesized and structurally characterized. Compounds La (1) and Pr (2) are isomorphous and exhibit 3D frameworks with the unique 1D tubular channels. Compounds Nd (3) and Eu (4) are 2D layer and 1D zigzag chain, respectively, which are further extended to 3D supramolecular frameworks through extensive hydrogen bonds. Isomorphous compounds of Gd (5) and Dy (6) are 3D frameworks constructed from secondary infinite rod-shaped metal-carboxylate/hydroxyl building blocks. While the hydroxyl groups as secondary functional groups in the 1D chain of Eu (4) and 2D layer of Nd (3) are not bonded to the lanthanide centers, the hydroxyl groups in the 3D frameworks of La (1), Pr (2), Gd (5), and Dy (6) participate in coordinating to lanthanide centers and thus modify the structural types of theses compounds. The magnetic data of compounds Pr (2), Nd (3), Gd (5), and Dy (6) have been investigated in detail. In addition, elemental analysis, IR spectra, powder X-ray diffraction (PXRD) patterns and thermogravimetric analysis of these compounds are described.