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Eu(O 2 C‐C≡C‐CO 2 ): An Eu II Containing Anhydrous Coordination Polymer with High Stability and Negative Thermal Expansion
Author(s) -
Gramm Verena K.,
Smets Daniel,
Grzesiak Ireneus,
Block Theresa,
Pöttgen Rainer,
Suta Markus,
Wickleder Claudia,
Lorenz Thomas,
Ruschewitz Uwe
Publication year - 2020
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201904966
Subject(s) - photoluminescence , anhydrous , analytical chemistry (journal) , thermal expansion , thermal stability , spectral line , oxygen , materials science , crystallography , chemistry , physics , optoelectronics , organic chemistry , chromatography , astronomy , metallurgy
Anhydrous Eu II –acetylenedicarboxylate (EuADC; ADC 2− = − O 2 C‐C≡C‐CO 2 − ) was synthesized by reaction of EuBr 2 with K 2 ADC or H 2 ADC in degassed water under oxygen‐free conditions. EuADC crystallizes in the SrADC type structure ( I 4 1 / amd , Z= 4) forming a 3D coordination polymer with a diamond‐like arrangement of Eu 2+ nodes ( msw topology including the connecting ADC 2− 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 ( μ eff =7.76 μ B ) and 151 Eu Mössbauer spectra ( δ =−13.25 mm s −1 at 78 K) confirm the existence of Eu 2+ cations. Diffuse reflectance spectra indicate a direct optical band gap of E g =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 α V =−9.4(12)×10 −6 K −1 .