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

Victoria E Gontcharenko; Mikhail A Kiskin; Vladimir D Dolzhenko; Vladislav M Korshunov; Ilya V Taydakov; Yury A Belousov

doi:10.3390/molecules26092655

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

Molecules. 2021 May 1;26(9):2655. doi: 10.3390/molecules26092655.

Authors

Victoria E Gontcharenko¹, Mikhail A Kiskin², Vladimir D Dolzhenko^{1

3}, Vladislav M Korshunov^{4

5}, Ilya V Taydakov^{4

6}, Yury A Belousov^{1

4}

Affiliations

¹ Chemistry Department, Moscow State University, Leninskie Gory, 119991 Moscow, Russia.
² Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, 119991 Moscow, Russia.
³ N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky pr. 47, 119991 Moscow, Russia.
⁴ P. N. Lebedev Physical Institute of Russian Academy of Sciences, 119991 Moscow, Russia.
⁵ Faculty of Fundamental Sciences, Bauman Moscow State Technical University, 105005 Moscow, Russia.
⁶ Academic Department of Innovational Materials and Technologies Chemistry, Plekhanov Russian University of Economics, 117997 Moscow, Russia.

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 [Eu_xTb_1-xL₃(H₂O)₂] (Eu_xTb_1-xL₃), [EuxGd_1-xL₃(H₂O)₂] (Eu_xGd_1-xL₃), and [Gd_xTb_1-xL₃(H₂O)₂] (Gd_xTb_1-xL₃), were studied. The Eu_xTb_1-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.

Keywords: color tuning; diketones; energy transfer; europium; gadolinium; lanthanides; luminescence; pyrazoles; terbium.

Grants and funding

20-33-70208/RFBR