Rare‐Earth Melonates LnC6N7(NCN)3·xH2O (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
Rare‐Earth Melonates LnC6N7(NCN)3·xH2O (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
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DOI：
10.1002/ejic.201101251
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发表时间：
2012-04
影响因子：
2.3
通讯作者：
Sophia J. Makowski;A. Schwarze;P. Schmidt;W. Schnick
中科院分区：
文献类型：
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作者：
Sophia J. Makowski;A. Schwarze;P. Schmidt;W. Schnick
通过水溶液复分解反应合成了稀土钼酸盐LnC 6 N7（NCN）3·xH 2 O（Ln = La，Ce，Pr，Nd，Sm，Eu，Tb; x = 8-12），并通过单晶和粉末XRD，FTIR，热分析和光致发光研究进行了表征。粉末XRD图谱显示La-Sm化合物具有类质同型性。LaC_6N_7（NCN）_3·8H_2O的晶体结构由单晶衍射数据解析和精修，其余盐的晶体结构由粉末XRD数据用Rietveld精修法精修。在晶体结构中，丙二酸盐实体排列在波纹层中，其与结晶水分子层交替。镧系离子由两个丙二酸盐和六个水分子配位。对LnC_6N_7（NCN）_3·xH_2O（Ln = Eu，Tb; x = 9-12）进行了光致发光研究。无论是水合或脱水的铕的丙二酸盐在紫外光激发下表现出发光，而光致发光的研究丙二酸铽显示绿色发射，最大值在545 nm处，由于5D47 F5过渡。热分析表明，相当低的热稳定性的稀土甜瓜，这可能是由于紧密结合的结晶水，在高温下水解分解的结果。
The rare-earth melonates LnC6N7(NCN)3·xH2O (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 LaC6N7(NCN)3·8H2O 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. LnC6N7(NCN)3·xH2O (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 5D47F5 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.