Pyrazine Dicarboxylic Acid and Phosphite-Bridging Lanthanide-Incorporated Tellurotungstates and Their Fluorescence Performances

Abstract

Two pyrazine dicarboxylic acid and phosphite-bridging lanthanide-incorporated tellurotungstates [H 2 N(CH 3 ) 2 ] 1 2 Na 4 [Ln 4 (H 2 O) 2 (H 2 PDBA) 2 (HPO 3 ) 2 W 6 O 10 ][B-α-TeW 8 O 31 ] 4 • 70H 2 O [Ln = Eu 3+ (1), Tb 3+ (2); H 2 PDBA = 2,5-pyrazine dicarboxylic acid) were prepared, which contain four [B-α-TeW 8 O 31 ] 10− subunits and a decanuclear heterometallic [Ln(H 2moieties to form the polyanion skeleton, while the phosphite plays a bridging role in joining two lanthanide centers in the {W 3 Eu 2 O 5 (H 2 O)(B-α-Te-W 8 O 31 ) 2 (HP III O 3 )} 8− moiety. In addition to the fluorescence (FL) properties of 1 and 2 at room temperature, their temperature-dependent FL properties were also investigated. In 80−298 K, FL intensities of 1 and 2 decrease as temperature increases, and their maximum relative sensitivities (S r ) are 3.70 and 1.99% K −1 , whereas the minimum temperature uncertainties (δT) are 1.25 and 1.18 K for 1 and 2. In 298−973 K, upon increasing temperature, FL intensities of 1 and 2 initially rise to their maxima at 373 K and subsequently decrease. This is because samples of 1 and 2 undergo dehydration together with amorphization below 473 K and decomposition above this temperature. This work lays a foundation for the development for luminescent thermometers based on lanthanide-incorporated polyoxometalates.