Han Qing, Wen Yue, Liu Jian-Cai, Zhang Wu, Chen Li-Juan, Zhao Jun-Wei
Henan Key Laboratory of Polyoxometalate Chemistry, Institute of Molecule and Crystal Engineering, College of Chemistry and Chemical Engineering, Henan University , Kaifeng, Henan 475004, People's Republic of China.
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences , Fuzhou, Fujian 350002, People's Republic of China.
Inorg Chem. 2017 Nov 6;56(21):13228-13240. doi: 10.1021/acs.inorgchem.7b02009.
A series of organic-inorganic rare-earth-incorporated tellurotungstate hybrids, Na[RE(HO)(pica)WO][(RE(HO)W(Hpica)O)(B-β-TeWOH)]·38HO (RE = La (1), Ce (2), Nd (3), Sm (4), Eu (5); Hpica = 2-picolinic acid), were prepared via a one-step assembly reaction of NaWO·2HO, RE(NO)·6HO, KTeO, Hpica, and triethylamine (tea). Notably, the solubilization of tea toward Hpica and the solubilization of Hpica toward RE cations in the reaction system play an important role in the formation of 1-5. The most significant feature of 1-5 consists of an intriguing tetrameric [RE(HO)(pica)WO][(RE(HO)W(Hpica)O)(B-β-TeWOH)] polyoxoanion constructed from two tetravacant Keggin sandwich-type [(RE(HO)W(Hpica)O)(B-β-TeWOH)] entities linked by a RE-W-Hpica {RE(HO)(pica)WO} cluster, in which Hpica ligands not only play a key bridging role in linking RE and W centers by carboxylic groups in an irregular N-O-RE-O-W-O six-membered-ring motif but also can directly chelate with W centers via N and O atoms in a stable N-O-C-O-W five-membered-ring fashion. 1-5 represent rare organic-inorganic hybrid RE-substituted tellurotungstates. Moreover, the solid-state photoluminescence properties of 3-5 have been deeply investigated, and these compounds exhibit the characteristic emission stemming from intra-4f transitions of RE ions. The energy transfer of the O → W transitions sensitizing the emission of Sm centers in 4 is convincingly proved by time-resolved emission spectra (TRES); the increase in the strongest typical emission of Sm ions at a decay time of 17 μs is accompanied by the decline of O → W emission, and the CIE 1931 diagram was obtained from the corresponding TRES. Furthermore, a comparison of the luminescence behaviors of 5 in the solid state and in solution reveals the structural skeletal integrity of 5 in solution and a shorter decay lifetime in the solution caused by the high-frequency O-H oscillators.
通过Na₂WO₄·2H₂O、RE(NO₃)₃·6H₂O、K₂TeO₃、2-吡啶甲酸（Hpica）和三乙胺（tea）的一步组装反应，制备了一系列有机-无机稀土掺杂碲钨酸盐杂化物Na[RE(HO)(pica)WO₄][(RE(HO)W(Hpica)O)(B-β-TeW₁₀O₃₉)]·38H₂O（RE = La (1)、Ce (2)、Nd (3)、Sm (4)、Eu (5)）。值得注意的是，tea对Hpica的增溶作用以及Hpica对反应体系中RE阳离子的增溶作用在1-5的形成中起着重要作用。1-5最显著的特征是由一个有趣的四聚体[RE(HO)(pica)WO₄][(RE(HO)W(Hpica)O)(B-β-TeW₁₀O₃₉)]多氧阴离子构成，该多氧阴离子由两个四空位Keggin夹心型[(RE(HO)W(Hpica)O)(B-β-TeW₁₀O₃₉)]实体通过一个RE-W-Hpica {RE(HO)(pica)WO₄}簇连接而成，其中Hpica配体不仅在通过羧基以不规则的N-O-RE-O-W-O六元环模式连接RE和W中心时起关键的桥连作用，还能通过N和O原子以稳定的N-O-C-O-W五元环方式直接与W中心螯合。1-5代表了罕见的有机-无机杂化RE取代碲钨酸盐。此外，对3-5的固态光致发光性质进行了深入研究，这些化合物表现出源于RE离子4f内跃迁的特征发射。通过时间分辨发射光谱（TRES）令人信服地证明了4中O→W跃迁对Sm中心发射的能量转移；在17 μs的衰减时间处，Sm离子最强典型发射的增加伴随着O→W发射的下降，并从相应的TRES获得了CIE 1931色度图。此外，对5在固态和溶液中的发光行为的比较揭示了5在溶液中的结构骨架完整性以及由高频O-H振荡器导致的溶液中较短的衰减寿命。
