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Rare‐Earth Melonates LnC 6 N 7 (NCN) 3 · x H 2 O (Ln = La, Ce, Pr, Nd, Sm, Eu, Tb; x = 8–12): Synthesis, Crystal Structures, Thermal Behavior, and Photoluminescence Properties of Heptazine Salts with Trivalent Cations
Author(s) -
Makowski Sophia J.,
Schwarze Arne,
Schmidt Peter J.,
Schnick Wolfgang
Publication year - 2012
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201101251
Subject(s) - photoluminescence , chemistry , terbium , lanthanide , europium , luminescence , crystallography , crystal structure , thermal decomposition , single crystal , powder diffraction , rietveld refinement , crystal (programming language) , molecule , x ray crystallography , analytical chemistry (journal) , inorganic chemistry , ion , materials science , diffraction , physics , optoelectronics , organic chemistry , optics , computer science , programming language , chromatography
The rare‐earth melonates LnC 6 N 7 (NCN) 3 · x H 2 O (Ln = La, Ce, Pr, Nd, Sm, Eu, Tb; x = 8–12) have been synthesized by metathesis reactions in aqueous solution and characterized by single‐crystal and powder XRD, FTIR spectroscopy, thermal analysis, and photoluminescence studies. Powder XRD patterns revealed isotypism of the La–Sm compounds. The structure of LaC 6 N 7 (NCN) 3 · 8H 2 O has been solved and refined from single‐crystal diffraction data and those of the remaining salts have been refined from powder XRD data by Rietveld refinement. In the crystal structures, the melonate entities are arranged in corrugated layers, which alternate with layers of crystal water molecules. The lanthanide ions are coordinated by two melonate and six water molecules. LnC 6 N 7 (NCN) 3 · x H 2 O (Ln = Eu, Tb; x = 9–12) have also been investigated by photoluminescence studies. Neither hydrated nor dehydrated europium melonate exhibits luminescence under UV excitation, whereas photoluminescence studies of terbium melonate showed green emission with a maximum at 545 nm due to the 5 D 4 → 7 F 5 transition. Thermal analysis revealed rather low thermal stability of the rare‐earth melonates, which is probably due to the tight binding of crystal water that results in hydrolytic decomposition at elevated temperatures.