Syntheses, structures and fluorescence properties of three rare-earth containing docosatungstates.

Three rare-earth containing docosatungstates Na3 H2 [RE(H2 O)4 ][RE(H2 O)5 ]2 [W22 O74 H2 ]·36H2 O [RE=DyIII (1), HoIII (2), YIII (3)] have been synthesized by reaction of Na2 WO4 ·2H2 O, dimethylamine hydrochloride (DMAHC) and RE(NO3 )3 ·6H2 O in the aqueous solution and characterized by elemental analyses, IR spectra, thermogravimetric (TG) analysis, powder X-ray diffraction (PXRD) and single-crystal X-ray diffraction. 1-3 are isomorphous and each molecular unit consists of a S-shaped docosatungstate [W22 O74 H2 ]14- polyoxoanion with two supporting [RE(H2 O)5 ]3+ cations and one disordered [RE(H2 O)4 ]3+ cation. The [W22 O74 H2 ]14- polyoxoanion can be viewed as combination of two hendecatungstate [W11 O38 H]9- subunits in the staggered fashion by sharing two μ2 -O atoms. The TG curves of 1-3 reveal the one-step weight loss between 25°C to 700°C. Moreover, both 1 and 2 demonstrate the characteristic luminescence emission behaviors of the corresponding RE3+ ions and their lifetime decay curves can be well fitted to the double exponential function. In addition, the CIE chromaticity coordinates of 1 and 2 have been obtained based on their corresponding emission spectra, and their dominant wavelengths and color purities have been also calculated.