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The crystal structures of {LnCu₅}³⁺ (Ln = Gd, Dy and Ho) 15-metallacrown-5 complexes and a reevaluation of the isotypic Eu^III analogue.

ABSTRACT: Three new isotypic heteropolynuclear complexes, namely penta-aqua-carbonato-penta-kis-(glycinehydroxamato)nitrato-penta-copper(II)lanthanide(III) x-hydrate, [LnCu₅(GlyHA)₅(CO₃)(NO₃)(H₂O)₅]·xH₂O (GlyHA^2- is glycine-hydrox-amate, N-hy-droxy-glycinamidate or amino-aceto-hydroxamate, C₂H₄N₂O₂ ^2-), with lanthanide(III) (Ln ^III) = gadolinium (Gd, 1, x = 3.5), dysprosium (Dy, 2, x = 3.28) and holmium (Ho, 3, x = 3.445), within a 15-metallacrown-5 class were obtained on reaction of lanthanide(III) nitrate, copper(II) acetate and sodium glycinehydroxamate. Complexes 1-3 contain five copper(II) ions and five bridging GlyHA^2- anions, forming a [CuGlyHA]₅ metallamacrocyclic core. The Ln ^III ions are coordinated to the metallamacrocycle through five O-donor hydroxamates. The electroneutrality of complexes 1-3 is achieved by a bidentate carbonate anion coordinated to the Ln ^III ion and a monodentate nitrate anion coordinated apically to one of the copper(II) ions of the metallamacrocycle. The lattice parameters of complexes 1-3 are similar to those previously reported for an Eu^III-Cu^II 15-metallacrown-5 complex with glycine-hydroxamate of proposed composition [EuCu₅(GlyHA)₅(OH)(NO₃)₂(H₂O)₄]·3.5H₂O [Stemmler et al. (1999 ?). Inorg. Chem. 38, 2807-2817]. High-quality X-ray data obtained for 1-3 have allowed a re-evaluation of the X-ray data solution proposed earlier for the EuCu₅ complex and suggest that the formula is actually [EuCu₅(GlyHA)₅(CO₃)(NO₃)(H₂O)₅]·3.5H₂O.

SUBMITTER: Pavlishchuk A

PROVIDER: S-EPMC6690475 | biostudies-literature | 2019 Aug

REPOSITORIES: biostudies-literature

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The crystal structures of {LnCu5}3+ (Ln = Gd, Dy and Ho) 15-metallacrown-5 complexes and a reevaluation of the isotypic EuIII analogue.

Pavlishchuk Anna A Naumova Dina D Zeller Matthias M Calderon Cazorla Sebastian S Addison Anthony W AW

Acta crystallographica. Section E, Crystallographic communications 20190719 Pt 8

Three new isotypic heteropolynuclear complexes, namely penta-aqua-carbonato-penta-kis-(glycinehydroxamato)nitrato-penta-copper(II)lanthanide(III) x-hydrate, [LnCu5(GlyHA)5(CO3)(NO3)(H2O)5]·xH2O (GlyHA2- is glycine-hydrox-amate, N-hy-droxy-glycinamidate or amino-aceto-hydroxamate, C2H4N2O2 2-), with lanthanide(III) (Ln <s ...[more]

PMID: 31417795

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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

The crystal structures of {LnCu₅}³⁺ (Ln = Gd, Dy and Ho) 15-metallacrown-5 complexes and a reevaluation of the isotypic Eu^III analogue.

Publications

The crystal structures of {<i>Ln</i>Cu<sub>5</sub>}<sup>3+</sup> (<i>Ln</i> = Gd, Dy and Ho) 15-metallacrown-5 complexes and a reevaluation of the isotypic Eu<sup>III</sup> analogue.

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