Novel trivalent europium β-diketonate complexes with N-(pyridine-2-yl)amides and N-(pyrimidine-2-yl)amides as ancillary ligands: photophysical properties and theoretical structural modeling

Eighteen new Eu3+ complexes and their Gd3+ analogues with 1,3-diketonate as main ligands and N-(pyridine-2-yl)amides or N-(pyrimidine-2-yl)amides as ancillary ligands were synthesized. The replacement of water molecules by those amides in the Eu3+ complexes increase the intrinsic quantum yields of luminescence, making them comparable or even more efficient than Eu3+ complexes with standard ancillary ligands such as 2,2′-bipyridine. The luminescence spectra of Gd3+ complexes in comparison with the Eu3+ ones show that efficient ligand-to-metal intramolecular energy transfer processes take place. In most cases the experimental Judd-Ofelt intensity parameters (Ω2 and Ω4) for the Eu3+ complexes show variations as a function of the temperature (77 and 300 K) that overall apparently does not follow clearly any trend. For this reason, geometric variations (on the azimuthal angle φ and ancillary ligands distances) were carried out in the coordination polyhedron for simulating thermally induced structural changes. It has been observed that, in this way, the Ω2 and Ω4 can be satisfactorily reproduced by in silico experiments. It was concluded that, at low-temperature, the ancillary ligands become closer to the Eu3+ ion and the angular variations affect more Ω2 than Ω4, in agreement to the theoretical calculations. The use of N-(pyridine-2-yl)amides or N-(pyrimidine-2-yl)amides as ancillary ligands in Eu3+ 1,3-diketonates looks to be a good strategy for obtaining highly luminescent complexes.publishe

Red-Green Emitting and Superparamagnetic Nanomarkers Containing Fe₃O₄ Functionalized with Calixarene and Rare Earth Complexes

The design of bifunctional magnetic luminescent nanomaterials containing Fe₃O₄ functionalized with rare earth ion complexes of calixarene and β-diketonate ligands is reported. Their preparation is accessible through a facile one-pot method. These novel Fe₃O₄@calix-Eu­(TTA) (TTA = thenoyltrifluoroacetonate) and Fe₃O₄@calix-Tb­(ACAC) (ACAC = acetylacetonate) magnetic luminescent nanomaterials show interesting superparamagnetic and photonic properties. The magnetic properties (M-H and ZFC/FC measurements) at temperatures of 5 and 300 K were explored to investigate the extent of coating and the crystallinity effect on the saturation magnetization values and blocking temperatures. Even though magnetite is a strong luminescence quencher, the coating of the Fe₃O₄ nanoparticles with synthetically functionalized rare earth complexes has overcome this difficulty. The intramolecular energy transfer from the T₁ excited triplet states of TTA and ACAC ligands to the emitting levels of Eu³⁺ and Tb³⁺ in the nanomaterials and emission efficiencies are presented and discussed, as well as the structural conclusions from the values of the 4f–4f intensity parameters in the case of the Eu³⁺ ion. These novel nanomaterials may act as the emitting layer for the red and green light for magnetic light-converting molecular devices (MLCMDs)

Red-Green Emitting and Superparamagnetic Nanomarkers Containing Fe₃O₄ Functionalized with Calixarene and Rare Earth Complexes

The design of bifunctional magnetic luminescent nanomaterials containing Fe₃O₄ functionalized with rare earth ion complexes of calixarene and β-diketonate ligands is reported. Their preparation is accessible through a facile one-pot method. These novel Fe₃O₄@calix-Eu­(TTA) (TTA = thenoyltrifluoroacetonate) and Fe₃O₄@calix-Tb­(ACAC) (ACAC = acetylacetonate) magnetic luminescent nanomaterials show interesting superparamagnetic and photonic properties. The magnetic properties (M-H and ZFC/FC measurements) at temperatures of 5 and 300 K were explored to investigate the extent of coating and the crystallinity effect on the saturation magnetization values and blocking temperatures. Even though magnetite is a strong luminescence quencher, the coating of the Fe₃O₄ nanoparticles with synthetically functionalized rare earth complexes has overcome this difficulty. The intramolecular energy transfer from the T₁ excited triplet states of TTA and ACAC ligands to the emitting levels of Eu³⁺ and Tb³⁺ in the nanomaterials and emission efficiencies are presented and discussed, as well as the structural conclusions from the values of the 4f–4f intensity parameters in the case of the Eu³⁺ ion. These novel nanomaterials may act as the emitting layer for the red and green light for magnetic light-converting molecular devices (MLCMDs)

Experimental and theoretical investigations of the [Ln(β-dik)(NO3)2(phen)2]⋅H2O luminescent complexes

In this work, the coordination compounds presenting the formulas [Eu(acac)(NO3)2 (phen)2]⋅H2O (Eu1) and [Eu(bzac)(NO3)2(phen)2]⋅H2O (Eu2), acac: acetylacetonate, bzac: benzoylacetonate and, phen: 1,10-phenantroline, were successfully synthesized and some spectroscopic properties were investigated by theoretical and experimental methods. These compounds were characterized via elemental analysis, FTIR spectroscopy and thermogravimetric analysis (TGA). The X-ray diffraction data revealed that the compound Eu1 crystallizes in the monoclinic space group P2/n. Spectroscopic data showed that ligand-to-metal charge transfer states (LMCT) in the [Eu(β-dik)(NO3)2(phen)2]⋅H2O complexes (β-dik: acac or bzac) are redshift as compared with [Eu(β-dik)3(phen)] complexes. These data showed that LMCT states play the most important role on the luminescence quenching in the complexes Eu1 and Eu2, which only exhibit high luminescence intensities at low temperatures. Furthermore, the role of changes in the chemical environment on the intensity parameters Ωλ (λ = 2 and 4) have been investigated from the theoretical point of view for the complexes Eu1 to Eu2, and from these to tris β–dik complexes. Interestingly, the theoretical intensity parameters ratio Ω2/Ω4 calculated are in a good agreement with those experimental ones.publishe