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The unprecedented borate hydride Sr5(BO3)3H and deuteride Sr5(11BO3)3D crystallizing in an apatite‐related structure are reported. Despite the presence of hydride anions, the compound decomposes only slowly in air. Doped with Eu2+, it shows broad‐band orange‐red emission under violet excitation owing to the 4f65d–4f7 transition of Eu2+. The observed 1H NMR chemical shift is in good agreement with previously reported 1H chemical shifts of ionic metal hydrides as well as with quantum chemical calculations and very different from 1H chemical shifts usually found for hydroxide ions in similar materials. FTIR and Raman spectroscopy of different samples containing 1H, 2H, natB, and 11B combined with calculations unambiguously prove the absence of hydroxide ions and the sole incorporation of hydride ions into the borate. The orange‐red emission obtained by doping with Eu2+ shows that the new compound class might be a promising host material for optical applications. [ABSTRACT FROM AUTHOR]

Inorganic hosts, such as SrB4O7 or certain nitrides, intrinsically stabilize Eu2+ even when the dopant is an Eu3+‐based precursor and reducing conditions are not employed in the synthesis. Although this concept is well known in the synthesis of phosphorescent materials, the mechanistic details are scarcely understood. Herein, we demonstrate that trapped charge carriers, such as color centers, can also act as redox partners to stabilize certain oxidation states of activators. Eu‐activated CsMgCl3 and CsMgBr3 are used as examples. Upon doping with EuCl3 and in the absence of reducing conditions during the synthesis, dominant cyan or green luminescence from Eu2+ ions was observed. Photoluminescence spectroscopy at 10 K revealed that the reduction is correlated to color centers localized at defects. Although defects are typically undesired in phosphors, we have shown that their role may be underestimated and they could be used on purpose in the preparation of selected inorganic phosphors. [ABSTRACT FROM AUTHOR]

Anorganische Wirtsverbindungen wie SrB4O7 oder ausgewählte Nitride können Eu2+ intrinsisch stabilisieren, selbst wenn Eu3+‐Ausgangsmaterialien und keine reduzierenden Bedingungen in der Synthese genutzt werden. Obwohl dies im Bereich der Leuchtstoffsynthese bekannt ist, sind mechanistische Details nur unzureichend verstanden. Hier zeigen wir, dass lokalisierte Ladungsträger wie Farbzentren auch als Redoxpartner agieren können, um bestimmte Oxidationszustände von Aktivatoren zu stabilisieren. Die Eu‐dotierten Verbindungen CsMgCl3 und CsMgBr3 dienen als Beispiele. Selbst bei gezielter Dotierung mit EuCl3 und Ausschluss reduzierender Bedingungen kann aufgrund von Eu2+ cyane bzw. grüne Lumineszenz beobachtet werden. Photolumineszenzspektroskopie bei 10 K zeigte, dass diese intrinsische Reduktion mit Farbzentren korreliert, die an Verunreinigungen lokalisiert sind. Obgleich Defekte in Leuchtstoffen unerwünscht sind, zeigt diese Studie, dass ihre Rolle oft unterschätzt wird und sie gezielt in der Präparation ausgewählter anorganischer Leuchtstoffe genutzt werden könnten. [ABSTRACT FROM AUTHOR]

Anhydrous EuII–acetylenedicarboxylate (EuADC; ADC2− = −O2C‐C≡C‐CO2−) was synthesized by reaction of EuBr2 with K2ADC or H2ADC in degassed water under oxygen‐free conditions. EuADC crystallizes in the SrADC type structure (I41/amd, Z=4) forming a 3D coordination polymer with a diamond‐like arrangement of Eu2+ nodes (msw topology including the connecting ADC2− linkers). Deep orange coloured EuADC is stable in air and starts decomposing upon heating in an argon atmosphere only at 440 °C. Measurements of the magnetic susceptibilities (μeff=7.76 μB) and 151Eu Mössbauer spectra (δ=−13.25 mm s−1 at 78 K) confirm the existence of Eu2+ cations. Diffuse reflectance spectra indicate a direct optical band gap of Eg=2.64 eV (470 nm), which is in accordance with the orange colour of the material. Surprisingly, EuADC does not show any photoluminescence under irradiation with UV light of different wavelengths. Similar to SrADC, EuADC exhibits a negative thermal volume expansion below room temperature with a volume expansion coefficient αV=−9.4(12)×10−6 K−1. [ABSTRACT FROM AUTHOR]

The series of homoleptic lanthanide(ii) “bent sandwich-like” hydro-tris(pyrazolyl)borate complexes Ln(TpiPr2)2 (Ln = Sm (1), Eu (2), Tm (3), Yb (4); TpiPr2 = hydro-tris(3,5-diisopropylpyrazolyl)borate) has been completed by the synthesis of the hitherto unknown europium and ytterbium derivatives 2 and 4. Both compounds were prepared in high yields by treatment of LnI2(THF)2 (Ln = Eu, Yb) with 2 equiv. of KTpiPr2 in a THF solution. Although the molecules are sterically highly congested, an X-ray diffraction study of bright red 4 revealed a similar bent B–Yb–B arrangement (151.1° and 153.9°, two independent molecules) as in the previously investigated Sm(ii) and Tm(ii) complexes 1 and 3. An initial reactivity study showed a very different behavior with acetonitrile. While 2 and 4 proved to be unreactive toward acetonitrile, the more strongly reducing Sm(ii) complex 1 yielded two new products. The major product was the dark green-black acetonitrile solvate SmII(TpiPr2)2·CH3CN (5), while the second product, the colorless (TpiPr2)SmIII(3,5-iPr2pz)2(NCCH3) (6) with two 3,5-diisopropyl-pyrazolate ligands, resulted from oxidation of samarium to the trivalent state and degradation of a TpiPr2 ligand. Disappointingly, from the most reducing Tm(ii) complex 3 only the ligand fragmentation product pyrazabole, [HB(3,5-iPr2pz)2]2 (7), could be isolated and the fate of the Tm containing by-product(s) remains unknown. The new compounds 4–6 were structurally authenticated through single-crystal X-ray diffraction. The europium compound 2 shows an extremely bright yellow emission in solution, which can be observed also at daylight excitation, as well as in the solid state. The high intensity is even remarkable when compared to other Eu(ii) containing materials. The photoluminescence was investigated with the conclusion that the rigidity of this complex is responsible for these outstanding luminescence properties. [ABSTRACT FROM AUTHOR]