4f-Orbital mixing increases the magnetic susceptibility of Cp'3Eu

Traditional models of lanthanide electronic structure suggest that bonding is predominantly ionic, and that covalent orbital mixing is not an important factor in determining magnetic properties. Here, 4f orbital mixing and its impact on the magnetic susceptibility of Cp'3Eu (Cp' = C5H4SiMe3) was analyzed experimentally using magnetometry and X-ray absorption spectroscopy (XAS) methods at the C K-, Eu M5,4-, and L3-edges. Pre-edge features in the experimental and TDDFT-calculated C K-edge XAS spectra provided unequivocal evidence of C 2p and Eu 4f orbital mixing in the π-antibonding orbital of a' symmetry. The charge-transfer configurations resulting from 4f orbital mixing were identified spectroscopically by using Eu M5,4-edge and L3-edge XAS. Modeling of variable-temperature magnetic susceptibility data showed excellent agreement with the XAS results and indicated that increased magnetic susceptibility of Cp'3Eu is due to removal of the degeneracy of the 7F1 excited state due to mixing between the ligand and Eu 4f orbitals.

Single-Ion Anisotropy and Intramolecular Interactions in CeIII and NdIII Dimers

This article reports the syntheses, characterization, structural description, together with magnetic and spectroscopic properties of two isostructural molecular magnets based on the chiral ligand N,N'-bis((1,2-diphenyl-(pyridine-2-yl)methylene)-(R,R/S,S)-ethane-1,2-diamine), L1, of general formula [Ln2(RR-L1)2(Cl6)]·MeOH·1.5H2O, (Ln = Ce (1) or Nd (2)). Multifrequency electron paramagnetic resonance (EPR), cantilever torque magnetometry (CTM) measurements, and ab initio calculations allowed us to determine single-ion magnetic anisotropy and intramolecular magnetic interactions in both compounds, evidencing a more important role of the anisotropic exchange for the NdIII derivative. The comparison of experimental and theoretical data indicates that, in the case of largely rhombic lanthanide ions, ab initio calculations can fail in determining the orientation of the weakest components, while being reliable in determining their principal values. However, they remain of paramount importance to set the analysis of EPR and CTM on sound basis, thus obtaining a very precise picture of the magnetic interactions in these systems. Finally, the electronic structure of the two complexes, as obtained by this approach, is consistent with the absence of zero-field slow relaxation observed in ac susceptibility.

Luminescent and magnetic bifunctional coordination complex based on a chiral tartaric acid derivative and europium

A new mononuclear europium complex incorporating the (+)-di-p-toluoyl-D-tartaric acid (D-H2DTTA) ligand, namely, catena-poly[tris{μ2-3-carboxy-2,3-bis[(4-methylphenyl)carbonyloxy]propanoato}tris(methanol)europium(III)], [Eu(C20H17O8)3(CH3OH)3] n , (I), has been synthesized and characterized by IR spectroscopy, elemental analysis, powder X-ray diffraction and single-crystal X-ray diffraction analysis. The structure analysis indicates that complex (I) crystallizes in the trigonal space group R3 and exhibits an infinite one-dimensional chain structure, in which the Eu3+ ion is surrounded by six O atoms from six D-HDTTA− ligands and three O atoms from three coordinated methanol molecules, thus forming a tricapped trigonal prism geometry. The D-H2DTTA ligand is partially deprotonated and adopts a μ1,6-coordination mode via two carboxylate groups to link adjacent Eu3+ ions, affording an infinite one-dimensional propeller-shaped coordination polymer chain along the c axis, with an Eu...Eu distance of 7.622 (1) Å. Moreover, C—H...π interactions lead to the formation of helical chains running along the c axis and the whole structure displays a snowflake pattern in the ab plane. The circular dichroism spectrum confirms the chirality of complex (I). The solid-state photoluminescence properties were also investigated at room temperature and (I) exhibits characteristic red emission bands derived from the Eu3+ ion (CIE 0.63, 0.32), with a reasonably long lifetime of 0.394 ms, indicating effective energy transfer from the ligand to the metal centre. In addition, a magnetic investigation reveals single-ion magnetic behaviour. The spin-orbit coupling parameter (λ) between the ground and excited states is fitted to be 360 (2) cm−1 through Zeeman perturbation. Therefore, complex (I) may be regarded as a chiral optical-magneto bifunctional material.

Solid-state luminescence properties, Hirshfeld surface analysis and DFT calculations of mononuclear lanthanide complexes (Ln = EuIII, GdIII, TbIII, DyIII) containing 4'-phenyl-2,2':6',2″-terpyridine

Four mononuclear lanthanide complexes containing 4'-phenyl-2,2':6',2″-terpyridine (ptpy), [Ln(NO₃)₃(ptpy) (H₂O)] (Ln = Eu (1), Gd (2), Tb (3), Dy (4)), were solvothermally synthesized and characterized via elemental analysis, infrared spectroscopy, thermogravimetric analysis, single-crystal X-ray diffraction, and powder X-ray diffraction. Hirshfeld surfaces and the solid-state luminescence properties of the complexes were investigated. The 3-D Hirshfeld surface and 2-D fingerprint plots show that the main interactions are the O H/H O intermolecular interactions in 1-4. Solid-state luminescence investigation reveals that Gd^III complex 2 displays a ligand-centered emission and the Eu^III, Tb^III and Dy^III complexes 1, 3 and 4 show the characteristic lanthanide-centered luminescence upon UV excitations. The Eu^III and Tb^III complexes exhibit red (CIE: 0.6549, 0.3447) and green (CIE: 0.3760, 0.5412) luminescence in the solid state with quantum yields of 16.8% and 0.8% and lifetimes of 0.545 and 0.043 ms, respectively. Density functional theory (DFT) calculations were conducted to unravel the HOMO-LUMO energy gaps of the structures of ptpy and complexes 1 and 3.

Synthesis of a dinuclear europium(iii) complex through deprotonation and oxygen-atom transfer of trimethylamine N-oxide

A dinuclear europium complex was synthesized via unprecedented deprotonation and oxygen-atom transfer of Me₃NO.

Magnetic and luminescent coordination networks based on imidazolium salts and lanthanides for sensitive ratiometric thermometry

The synthesis and characterization of six new lanthanide networks [Ln(L)(ox)(H₂O)] with Ln = Eu³⁺, Gd³⁺, Tb³⁺, Dy³⁺, Ho³⁺ and Yb³⁺ is reported. They were synthesized by solvo-ionothermal reaction of lanthanide nitrate Ln(NO₃)₃·xH₂O with the 1,3-bis(carboxymethyl)imidazolium [HL] ligand and oxalic acid (H₂ox) in a water/ethanol solution. The crystal structure of these compounds has been solved on single crystals and the magnetic and luminescent properties have been investigated relying on intrinsic properties of the lanthanide ions. The synthetic strategy has been extended to mixed lanthanide networks leading to four isostructural networks of formula [Tb_{1- x} Eu _x (L)(ox)(H₂O)] with x = 0.01, 0.03, 0.05 and 0.10. These materials were assessed as luminescent ratiometric thermometers based on the emission intensities of ligand, Tb³⁺ and Eu³⁺. The best sensitivities were obtained using the ratio between the emission intensities of Eu³⁺ (⁵D₀→⁷F₂ transition) and of the ligand as the thermometric parameter. [Tb_0.97Eu_0.03(L)(ox)(H₂O)] was found to be one of the best thermometers among lanthanide-bearing coordination polymers and metal-organic frameworks, operative in the physiological range with a maximum sensitivity of 1.38%·K^-1 at 340 K.

Hydrothermal synthesis, X-ray structure and DFT and magnetic studies of a (H2SiW12O40)2− based one-dimensional linear coordination polymer

In this paper, we report the synthesis and characterization of a novel POM-based inorganic–organic hybrid with an in situ transformation of pyridine-2,3-dicarboxylic acid into nicotinic acid and 2-hydroxynicotinic acid under hydrothermal conditions.

Synthesis of discrete Re(i) di- and tricarbonyl assemblies using a [4 × 1] directional bonding strategy

Discrete assembly of two Re(i) squares was achieved by a simple [4 × 1] strategy where the complexes, [Re(4-pytpy-κ²N)(CO)₃Br] and [Re(4-pytpy-κ³N)(CO)₂Br], act as their own ligands. The properties of the assemblies and their precursors are described along with solid-state X-ray diffraction studies.