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Eu(O2 C-C?C-CO2 ): An EuII Containing Anhydrous Coordination Polymer with High Stability and Negative Thermal Expansion.

ABSTRACT: Anhydrous EuII -acetylenedicarboxylate (EuADC; ADC2- = - O2 C-C?C-CO2 - ) was synthesized by reaction of EuBr2 with K2 ADC or H2 ADC 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 (?eff =7.76??B ) and 151 Eu Mössbauer spectra (?=-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 ?V =-9.4(12)×10-6 ?K-1 .

SUBMITTER: Gramm VK

PROVIDER: S-EPMC7065108 | biostudies-literature | 2020 Feb

REPOSITORIES: biostudies-literature

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Eu(O2 C-C≡C-CO2 ): An EuII Containing Anhydrous Coordination Polymer with High Stability and Negative Thermal Expansion.

Gramm Verena K VK Smets Daniel D Grzesiak Ireneus I Block Theresa T Pöttgen Rainer R Suta Markus M Wickleder Claudia C Lorenz Thomas T Ruschewitz Uwe U

Chemistry (Weinheim an der Bergstrasse, Germany) 20200211 12

Anhydrous EuII -acetylenedicarboxylate (EuADC; ADC2- = - O2 C-C≡C-CO2 - ) was synthesized by reaction of EuBr2 with K2 ADC or H2 ADC 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- ...[more]

PMID: 31774598

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Project description:Eu3+-activated Ba2Y5B5O17 (Ba2Y5-x Eu x B5O17; x = 0.1-1) red-emitting phosphors were synthesized by the conventional high temperature solid-state reaction method in an air atmosphere. Powder X-ray diffraction (XRD) analysis confirmed the pure phase formation of the as-synthesized phosphors. Morphological studies were performed using field emission-scanning electron microscopy (FE-SEM). The photoluminescence spectra, lifetimes, color coordinates and internal quantum efficiency (IQE) as well as the temperature-dependent emission spectra were investigated systematically. Upon 396 nm excitation, Ba2Y5-x Eu x B5O17 showed red emission peaking at 616 nm which was attributed to the 5D0 → 7F2 electric dipole transition of Eu3+ ions. Meanwhile, the influences of different concentrations of Eu3+ ions on the PL intensity were also discussed. The optimum concentration of Eu3+ ions in the Ba2Y5-x Eu x B5O17 phosphors was found to be x = 0.8. The concentration quenching mechanism was attributed to the dipole-dipole interaction and the critical distance (R c) for energy transfer among Eu3+ ions was determined to be 5.64 Å. The asymmetry ratio [(5D0 → 7F2)/(5D0 → 7F1)] of Ba2Y4.2Eu0.8B5O17 phosphors was calculated to be 3.82. The fluorescence decay lifetimes were also determined for Ba2Y5-x Eu x B5O17 phosphors. In addition, the CIE color coordinates of the Ba2Y4.2Eu0.8B5O17 phosphors (x = 0.653, y = 0.345) were found to be very close to the National Television System Committee (NTSC) standard values (x = 0.670, y = 0.330) of red emission and also showed high color purity (∼94.3%). The corresponding internal quantum efficiency of the Ba2Y4.2Eu0.8B5O17 sample was measured to be 47.2%. Furthermore, the as-synthesized phosphors exhibited good thermal stability with an activation energy of 0.282 eV. The above results revealed that the red emitting Ba2Y4.2Eu0.8B5O17 phosphors could be potential candidates for application in near-UV excited white light emitting diodes.

Dataset Information

Eu(O2 C-C?C-CO2 ): An EuII Containing Anhydrous Coordination Polymer with High Stability and Negative Thermal Expansion.

Publications

Eu(O<sub>2</sub> C-C≡C-CO<sub>2</sub> ): An Eu<sup>II</sup> Containing Anhydrous Coordination Polymer with High Stability and Negative Thermal Expansion.

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