Crystal Structures and Magnetic and Luminescent Properties of a Series of Homodinuclear Lanthanide Complexes with 4-Cyanobenzoic Ligand

Abstract

A series of homodinuclear lanthanide(III) complexes with the 4-cba ligand, [La2(4-cba)6(phen)2(H2O)6] (1) and [Ln2(4-cba)6(phen)2(H2O)2] (Ln = Pr (2), Nd (3), Sm (4), Eu (5), Gd (6), and Dy (7); 4-Hcba = 4-cyanobenzoic acid; phen = 1,10-phenanthroline), have been synthesized and structurally characterized by single-crystal X-ray diffraction. In 1, two water molecules bridge two nine-coordinated La ions, and six 4-cba ligands coordinate to the two La ions in terminal mode. In the isostructural complexes 2-7, two eight-coordinated Ln ions are connected by four bidentate 4-cba ligands, and another two 4-cba ligands terminate the two Ln ions. The variable-temperature magnetic properties of 2-7 have been investigated. Complex 7 shows a significant ferromagnetic interaction between Dy(III), while no magnetic interaction exists between Gd(III) ions in 6. In 2-5, the value of chi(M)T decreases with decreasing temperature, but the magnetic interactions between the Ln(III) ions cannot definitely be concluded. Notably, the spin-orbit coupling parameters, lambda, for Sm(III) (216(2) cm(-1)) and Eu(III) (404(2) cm(-1)) have been obtained in 4 and 5, respectively. The strong fluorescent emissions of 4, 5, and 7 demonstrate that ligand-to-Ln(III) energy transfer is efficient and that the coordinated water molecules do not quench their luminescence by the nonradiative dissipation of energy.

The Syntheses, Structures, and Magnetic Properties of Four 2D Lanthanide(III)‐naphthalenedicarboxylic Complexes

“…As illustrated in Figure 5, χ M T is equal to 1.57 emu·K·mol -1 at 300 K, which is close to the value expected for one isolated Nd III ion (1.64 emu·K·mol -1 ), [22] and decreases continuously to a value of 0.66 emu·K·mol -1 at 2 K. The curve of χ M -1 vs. T between 158 and 300 K follows the Curie-Weiss law with C = 1.83 emu·K·mol -1 and θ = -49.67 K ( Figure S2, Supporting Information), which is similar to those for the reported Nd III complexes [23] and also confirms the antiferromagnetic couplings between Nd III cations. With regard to Sm (4), the χ M T value decreases from 0.221 emu·K·mol -1 at 300 K to 0.036 emu·K·mol -1 at 2 K upon cooling ( Figure 6).…”

“…Moreover, the curve of χ M -1 vs. T does not obey the CurieWeiss law ( Figure S3, Supporting Information), which is similar to that reported for the Sm III complex. [23] …”

Extended Networks Generated from the Interaction of Rare‐Earth(III) Ions and Pyridine‐2‐carboxamide‐Based Ligands

“…The calculated λ value [45] leads to 285 cm -1 , which represents the energy gap between 7 F 0 and 7 F 1 ; this value is in the range of those generally observed for polynuclear Eu III complexes. [46][47][48] For 4, the χ M T value at 300 K is equal to 11.58 cm 3 K mol -1 , which is slightly lower than the calculated value of 11.82 cm 3 K mol -1 for the free Tb III ion. From 300 to 4 K, the χ M T value decreases slowly to 2.42 cm 3 K mol -1 ( Figure 8); this behavior is typical to the depopulation of the Stark levels.…”

Lanthanide Complexes Assembled from 3‐Fluorophthalate and 1,10‐Phenanthroline: Syntheses, Crystal Structure, Photoluminescence, and White‐Light Emission

“…[21] It has also been well-documented that the π-conjugated 1,10-phenanthroline (phen) ligand is an efficient sensitizer for both Eu III and Tb III , and is usually inserted into lanthanide carboxylate complexes. [10,[22][23][24] 3-Fluorophthalic acid (H 2 Fpht) is a suitable ligand for the preparation of luminescent lanthanide complexes. [25] Because fluorinated organic ligands have low-vibrational frequency of C-F (1220 cm -1 ), the luminescence intensity of complexes can be remarkably improved by reducing the fluorescence quenching effect of the vibrational C-H bond (the energy level C-H 2950 cm -1 ).…”