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Gas-Phase Structures of Potassium Tetrakis(hexafluoro- acetylacetonato) Lanthanide(III) Complexes [KLn(C₅ HF₆ O₂ )₄ ] (Ln=La, Gd, Lu).

ABSTRACT: The molecular structures of potassium tetrakis(hexafluoroacetylacetonato)lanthanide(III) complexes [KLn(hfa)₄ ] (Ln=La, Gd, Lu; hfa=C₅ HF₆ O₂ ,) were studied by synchronous gas-phase electron diffraction/mass spectrometry (GED/MS) supported by quantum-chemical (DFT/PBE0) calculations. The compounds sublime congruently and the vapors contain a single molecular species: the heterobinuclear complex [KLn(hfa)₄ ]. All molecules are of C₁ symmetry with the lanthanide atom in the center of an LnO₈ coordination polyhedron, while the potassium atom is coordinated by three ligands with formation of three K-O and three K-F bonds. One hfa ligand is not bonded to the potassium atom. Topological analysis of the electron-density distributions confirmed the existence of ionic-type K-O and K-F bonding. The structures of the free [KLn(hfa)₄ ] molecules are compared with those of the related compounds [KDy(hfa)₄ ] and [KEr(hfa)₄ ] in their crystalline state. The complex nature of the chemical bonding is discussed on the basis of electron-density topology analyses.

SUBMITTER: Girichev GV

PROVIDER: S-EPMC7839460 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature

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Publications

Gas-Phase Structures of Potassium Tetrakis(hexafluoro- acetylacetonato) Lanthanide(III) Complexes [KLn(C5 HF6 O2 )4 ] (Ln=La, Gd, Lu).

Girichev Georgiy V GV Giricheva Nina I NI Khochenkov Alexey E AE Sliznev Valery V VV Belova Natalya V NV Mitzel Norbert W NW

Chemistry (Weinheim an der Bergstrasse, Germany) 20201207 3

The molecular structures of potassium tetrakis(hexafluoroacetylacetonato)lanthanide(III) complexes [KLn(hfa)4 ] (Ln=La, Gd, Lu; hfa=C5 HF6 O2 ,) were studied by synchronous gas-phase electron diffraction/mass spectrometry (GED/MS) supported by quantum-chemical (DFT/PBE0) calculations. The compounds sublime congruently and the vapors contain a single molecular species: the heterobinuclear complex [KLn(hfa)4 ]. All molecules are of C1</su ...[more]

PMID: 33090541

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Project description:We have investigated the incorporation of the luminescent Eu3+ cation in different LnPO4 (Ln = Tb, Gd1-xLu x , x = 0.3, 0.5, 0.7, 1) host phases. All samples were analyzed with powder X-ray diffraction (PXRD), Raman spectroscopy, and site-selective time-resolved laser-induced luminescence spectroscopy (TRLFS) directly after synthesis and after an aging time of one year at ambient conditions. The PXRD investigations demonstrate the formation of a TbPO4 phase in an uncommon anhydrite-like crystal structure evoked by a pressure-induced preparation step (grinding). In the Gd1-xLu x PO4 solid solution series, several different crystal structures are observed depending on the composition. The TRLFS emission spectra of LuPO4, Gd0.3Lu0.7PO4, and Gd0.5Lu0.5PO4 indicate Eu3+-incorporation within a xenotime-type crystal structure. TRLFS and PXRD investigations of the Gd0.7Lu0.3PO4 composition show the presence of anhydrite, xenotime, and monazite phases, implying that xenotime no longer is the favored crystal structure due to the predominance of the substantially larger Gd3+-cation in this solid phase. Eu3+-incorporation occurs predominantly in the anhydrite-like structure with smaller contributions of Eu3+ incorporated in monazite and xenotime. The electronic levels of the Eu3+-dopant in Gd0.3Lu0.7PO4 and Gd0.5Lu0.5PO4 xenotime hosts are strongly coupled to external lattice vibrations, giving rise to high-energy peaks in the obtained excitation spectra. The coupling becomes stronger after aging to such an extent that direct excitation of Eu3+ in the xenotime structure is strongly suppressed. This phenomenon, however, is only visible for materials where Eu3+ was predominantly incorporated within the xenotime structure. Single crystals of Eu3+-doped LuPO4 show no changes upon aging despite the presence of vibronically coupled excitation peaks in the excitation spectra measured directly after synthesis. Based on this observation, we propose a lattice relaxation process occurring in the powder samples during aging, resulting in Eu3+ migration within the crystal structure and Eu3+ accumulation at grain boundaries or xenotime surface sites.

Dataset Information

Gas-Phase Structures of Potassium Tetrakis(hexafluoro- acetylacetonato) Lanthanide(III) Complexes [KLn(C₅ HF₆ O₂ )₄ ] (Ln=La, Gd, Lu).

Publications

Gas-Phase Structures of Potassium Tetrakis(hexafluoro- acetylacetonato) Lanthanide(III) Complexes [KLn(C<sub>5</sub> HF<sub>6</sub> O<sub>2</sub> )<sub>4</sub> ] (Ln=La, Gd, Lu).

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