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

Three rare-earth containing docosatungstates Na 3 H 2 [RE(H 2 O) 4 ][RE(H 2 O) 5 ] 2 [W 22 O 74 H 2 ]·36H 2 O [RE = Dy III ( 1 ), Ho III ( 2 ), Y III ( 3 )] have been synthesized by reaction of Na 2 WO 4 ·2H 2 O, dimethylamine hydrochloride (DMAHC) and RE(NO 3 ) 3 ·6H 2 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 [W 22 O 74 H 2 ] 14 − polyoxoanion with two supporting [RE(H 2 O) 5 ] 3 + cations and one disordered [RE(H 2 O) 4 ] 3 + cation. The [W 22 O 74 H 2 ] 14 − polyoxoanion can be viewed as combination of two hendecatungstate [W 11 O 38 H] 9 − subunits in the staggered fashion by sharing two μ 2 -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 RE 3 + 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. [ABSTRACT FROM AUTHOR]