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Syntheses, structures and fluorescence properties of three rare-earth containing docosatungstates
Hailou Li1, Yajie Liu1, Rui Zheng1
1Henan Key Laboratory of Polyoxometalate Chemistry, Institute of Molecular and Crystal Engineering, College of Chemistry and Chemical Engineering, Henan University, Kaifeng, Henan 475004, PR China.
Abstract:
Three rare-earth containing docosatungstates Na3H2[RE(H2O)4][RE(H2O)5]2[W22O74H2]·36H2O [RE=DyIII (1), HoIII (2), YIII (3)] have been synthesized by reaction of Na2WO4·2H2O, dimethylamine hydrochloride (DMAHC) and RE(NO3)3·6H2O 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 [W22O74H2]14- polyoxoanion with two supporting [RE(H2O)5]3+ cations and one disordered [RE(H2O)4]3+ cation. The [W22O74H2]14- polyoxoanion can be viewed as combination of two hendecatungstate [W11O38H]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.
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