Rare-Earth-Incorporated Tellurotungstate Hybrids Functionalized by 2-Picolinic Acid Ligands: Syntheses, Structures, and Properties

A series of organic–inorganic rare-earth-incorporated tellurotungstate hybrids, Na4[RE2(H2O)4(pica)2W2O5][(RE(H2O)W2(Hpica)2O4)(B-β-TeW8O30H2)2]2·38H2O (RE = LaIII (1), CeIII (2), NdIII (3), SmIII (4), EuIII (5); Hpica = 2-picolinic acid), were prepared via a one-step assembly reaction of Na2WO4·2H2O, RE(NO3)3·6H2O, K2TeO3, 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 [RE2(H2O)4(pica)2W2O5][(RE(H2O)W2(Hpica)2O4)(B-β-TeW8O30H2)2]24– polyoxoanion constructed from two tetravacant Keggin sandwich-type [(RE(H2O)W2(Hpica)2O4)(B-β-TeW8O30H2)2]5– entities linked by a RE–W–Hpica {RE2(H2O)4(pica)2W2O5}6+ 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...