Three Types of Distinguishing l-Alanine-Decorated and Rare-Earth-Incorporated Arsenotungstate Hybrids Prepared in a Facile One-Step Assembly Strategy.

Three kinds of distinguishing ala-decorated RE-incorporated (ala = l-alanine, RE = rare-earth) polytungstoarsenate hybrids containing {As2W19O68} building blocks [H2N(CH3)2]13Na3H2[Eu4W5(H2O)10(ala)3O14(As2W19O68)2]·35H2O (1), [H2N(CH3)2]12Na2H2[RE4W6(H2O)8(ala)4O15(OH)2(As2W19O68)2]·36H2O [RE = Gd3+ (2), Tb3+ (3)], and [H2N(CH3)2]12Na4[RE4W6(H2O)10(ala)2O15(OH)2(As2W19O68)2]·40H2O [RE = Dy3+ (4), Ho3+ (5), Er3+ (6), Yb3+ (7), Lu3+ (8)] were made in a facile one-step assembly strategy. The polyoxoanion skeletons of 1-8 are very similar, and all can be described as two [As2W19O68]16- moieties encapsulating an ala-decorated W-O-RE heterometallic cluster ([Eu4W5(H2O)10(ala)3O14]14+ for 1, [RE4W6(H2O)8(ala)4O15(OH)2]16+ for 2-3, and [RE4W6(H2O)10(ala)2O15(OH)2]16+ for 4-8, resulting in a four-leaf--clover-shaped tetrameric structure; however, the major discrepancy in the ala-decorated W-O-RE heterometallic clusters lies in the number of ala molecules equaling to three, four, and two, which may result from the various coordination geometries of RE ions and the different construction modes of W-O-RE heterometallic clusters. It should be emphasized that the carboxyl groups of ala ligands only coordinate to the W centers in 4-8, while they not only bridge the W centers together but also combine RE ions together in 1-3. Besides, the solid luminescent properties and lifetime decay behaviors of 1, 3, 4, 5, and 6 were systematically investigated at ambient temperature, and time-resolved fluorescence spectra of 1, 3, and 5 were also examined. Furthermore, the electrochemical response properties of composite CS-CMWCNs-1, 3, or 5/GCE electrochemical sensors toward the dopamine detection were investigated, which will offer the possibility of RE-incorporated polyoxometalates for acting as electrochemical response electrode materials.