Syntheses, structural characterization and photoluminescence properties of {AsO2(OH)}-bridging arsenotungstates incorporating lanthanide ions

Abstract Two {AsO 2 (OH)}-bridging lanthanide(Ln)-incorporated arsenotungstates (ATs) [H 2 N(CH 3 ) 2 ] 8 LnNa 5 {[W 3 Ln 2 (H 2 O) 8 AsO 8 (OH)][B-α-AsW 9 O 33 ] 2 } 2 ·65H 2 O [Ln = Er III ( 1 ), Yb III ( 2 )] were synthesized by reaction of Na 2 WO 4 ·2H 2 O, Ln(NO 3 ) 3 ·6H 2 O and NaAsO 2 in the presence of dimethylamine hydrochloride. The common structural features of 1 and 2 are that the As III ions not only act as heteroatoms of the AT fragments but also function as the bridging groups to link two identical {[W 3 Ln 2 (H 2 O) 8 AsO 8 (OH)][B-α-AsW 9 O 33 ] 2 } half-units. The results of TG analyses indicate that 1 and 2 undergo the similar three-step weight loss procedure between 25 and 800 °C. The first-step weight loss is attributable to the liberation of sixty-five lattice water molecules, the second-step weight loss corresponds to the release of sixteen coordination water molecules, ten protons as well as eight dimethylamine groups, and the third-step weight loss can be assigned to the sublimation of three As 2 O 3 molecules. In addition, the solid-state photoluminescence properties of 1 and 2 have been investigated and mainly demonstrate the characteristic emission behaviors of Er III ions and Yb III ions.