Mono- and Mixed Metal Complexes of Eu3+, Gd3+, and Tb3+ with a Diketone, Bearing Pyrazole Moiety and CHF2-Group: Structure, Color Tuning, and Kinetics of Energy Transfer between Lanthanide Ions

Abstract

Three novel lanthanide complexes with the ligand 4,4-difluoro-1-(1,5-dimethyl-1H-pyrazol-4-yl)butane-1,3-dione (HL), namely [LnL3(H2O)2], Ln = Eu, Gd and Tb, were synthesized, and, according to single-crystal X-ray diffraction, are isostructural. The photoluminescent properties of these compounds, as well as of three series of mixed metal complexes [EuxTb1-xL3(H2O)2] (EuxTb1-xL3), [EuxGd1-xL3(H2O)2] (EuxGd1-xL3), and [GdxTb1-xL3(H2O)2] (GdxTb1-xL3), were studied. The EuxTb1-xL3 complexes exhibit the simultaneous emission of both Eu3+ and Tb3+ ions, and the luminescence color rapidly changes from green to red upon introducing even a small fraction of Eu3+. A detailed analysis of the luminescence decay made it possible to determine the observed radiative lifetimes of Tb3+ and Eu3+ and estimate the rate of excitation energy transfer between these ions. For this task, a simple approximation function was proposed. The values of the energy transfer rates determined independently from the luminescence decays of terbium(III) and europium(III) ions show a good correlation.

Cinnamal Sensing and Luminescence Color Tuning in a Series of Rare-Earth Metal−Organic Frameworks with Trans-1,4-cyclohexanedicarboxylate

“…Instead, the photoexcitation is released through a phen-centered π*→π transition, which is usually not very effective, as a great deal of the energy is released through a nonemitting relaxation along multiple vibrational states of the antenna ligand. Keeping in mind that the compounds 1-3 are completely isostructural, the coordination matrix 1 with low luminescence activity can be employed for the dilution of photoactive Eu 3+ and/or Tb 3+ cations in the homogeneous crystalline phase [52][53][54][55][56][57]. Such lanthanide doping of the yttrium framework could (i) improve the luminescence efficiency by reducing the concentration quenching known for such luminophores (Eu 3+ , Tb 3+ ) and (ii) allow the mixing of the luminescence colors for more complex optical properties.…”

Highlighting Recent Crystalline Engineering Aspects of Luminescent Coordination Polymers Based on F-Elements and Ditopic Aliphatic Ligands

“…Moreover, the use of metallic connectors from 4f and 5f metals allows the development of materials with unique optical properties derived from their pure color emission, fine line f-transitions, and variable lifetime values depending on the desirable applications [12,15,22,23]. Additionally, the high coordination numbers and the oxophilic nature of these metallic centers [24,25] allow us to combine these ions with flexible carboxylate aliphatic ligands and build a "toolbox" to construct families of novel crystalline structures [26]. This work discusses some outstanding examples in structural variety of CPs using ditopic flexible ligands [−OOC-(CH 2 )n-COO−] and the role of the oxalate ligand as the first member of the dicarboxylate family, focusing on their luminescent properties, as well as applications such as dye photocatalysis and chemical and thermal sensing in Ln-CPs or An-CPs (Ln = lanthanides and An = actinides).…”

Crystal Structures, Thermal and Luminescent Properties of Gadolinium(III) Trans-1,4-cyclohexanedicarboxylate Metal-Organic Frameworks

“…The most intensive electron transitions in Gd 3+ occur in the ultraviolet region of 290-318 nm with the narrow-banded emission and have been applied in common lasers. Under a soft UV and visible excitation, Gd(III) is a non-emissive center and the luminescence of its coordination compounds is ligand-centered [15][16][17][18][19][20][21][22][23].…”