Organocounterions-Assisted and pH-Controlled Self-Assembly of Five Nanoscale High-Nuclear Lanthanide Substituted Heteropolytungstates

Five high-nuclear lanthanide (Ln) substituted heteropolytungstates [H2N(CH3)2]16Na9LnH10{[W16Ln10(H2O)38O50][B-α-SeW9O33]8}·56H2O [Ln = LaIII (1), CeIII (2)], [H2N(CH3)2]22Na4H12{[W18Ln10(H2O)34O56][B-α-SeW9O33]8}·80H2O [Ln = LaIII (3), CeIII (4)], and Na4[H2N(CH3)2]18H21[Nd(H2O)7][W16Nd10O50(H2O)34(B-α-AsW9O33)8]·60H2O (5) were prepared by reaction of Na2WO4·2H2O and Ln(NO3)3·6H2O in the presence of dimethylamine hydrochloride (DMAHC) and Na2SeO3 or NaAsO2 in an aqueous medium. The octameric polyoxoanions {[W16Ln10(H2O)38O50][B-α-SeW9O33]8}38– in 1 and 2 are assembled from eight [B-α-SeW9O33]8– building blocks linked by 16 extra bridging WVI centers and ten LnIII cations, whereas the octameric polyoxoanions {[W18Ln10(H2O)34O56][B-α-SeW9O33]8}38– in 3 and 4 are constructed from eight [B-α-SeW9O33]8– building blocks joined by 18 additional bridging WVI centers and ten LnIII cations [Ln = LaIII (3), CeIII (4)]. The octameric polyoxoanion [W16Nd10O50(H2O)34(B-α-AsW9O33)8]40– in 5 is constituted by eight [B-α-AsW9O33]9– building blocks connected by 16 extra bridging WVI centers and ten NdIII cations. It should be noted that neighboring {[W16Nd10(H2O)38O50][B-α-AsW9O33]8}46– polyoxoanions in 5 are further polymerized by two W–O–Nd–O–W linkers into a 1-D chain-like alignment. The thermolysis processes of 1, 4, and 5 were investigated by variable-temperature IR spectra, coloration changes, and variable-temperature PXRD patterns. The solid-state NIR luminescence properties of 5 were systematically studied at room temperature.