Yajie Liu

Trigonal Pyramidal {AsO2(OH)} Bridging Tetranuclear Rare-Earth Encapsulated Polyoxotungstate Aggregates

The one-pot assembly reaction of Na2WO4·2H2O, RE(NO3)3·6H2O, and NaAsO2 in the participation of dimethylamine hydrochloride as an organic solubilizing agent in the acidic aqueous solution led to a class of trigonal pyramidal {AsO2(OH)} bridging rare-earth substituted arsenotungstate (AT) aggregates [H2N(CH3)2]8Na8{[W3RE2(H2O)8AsO8(OH)][B-α-AsW9O33]2}2·65H2O [RE = Eu(III) (1), Gd(III) (2), Tb(III) (3), Dy(III) (4), Ho(III) (5), Y(III) (6)], which were structurally characterized by elemental analyses, IR spectra, single-crystal X-ray diffraction, and thermogravimetric (TG) analyses. The common structural feature of 1-6 is that their polyoxoanions consist of a novel tetrameric unit [(W3RE2(H2O)8AsO8(OH))(B-α-AsW9O33)2]2(16-) constituted by four trivacant Keggin [α-AsW9O33](9-) fragments linked through an unseen elliptical [W6RE4(H2O)16As2O16(OH)2](20+) moiety. Their polyoxoanionic infrastructures can also be described as a fusion of two equivalent dimeric subunits [(W3RE2(H2O)8O7)(B-α-AsW9O33)2](8-) bridged via two μ2-{AsO2(OH)} linkers. To the best of our knowledge, such a linking mode with trigonal pyramidal {AsO2(OH)} groups as linkers connecting adjacent RE containing polyoxometalate moieties together is very rare. The thermal stability of 1-6 was also investigated on the crystalline samples, and the thermal decomposition processes of 1, 4, and 6 were comparatively deeply studied. The fluorescent properties and decay times of 1, 3, and 4 were measured, and they exhibit the characteristic emissions of RE centers. The lifetimes of 1 and 3 mainly originate from the contribution of RE ions whereas the overall lifetime of 4 is contributed by the synergistic interactions of AT fragments and Dy(3+) ions.

Structural Transformation from Dimerization to Tetramerization of Serine-Decorated Rare-Earth-Incorporated Arsenotungstates Induced by the Usage of Rare-Earth Salts

Three types of serine-decorated rare- earth-containing arsenotungstate [H2 N(CH3 )2 ]6 NaH[RE2 W4 O10 (H2 O)8 (Ser)2 (B-α-AsW9 O33 )2 ]⋅30 H2 O (RE3+ =Eu3+ , Gd3+ , Tb3+ , Dy3+ , Ho3+ , Er3+ , Tm3+ , Yb3+ , and Y3+ ; 1), [H2 N(CH3 )2 ]6 Na6-x REx H4-2 x [RE4 W8 O19 (H2 O)10+y (OH)2 (Ser)2 (B-α-AsW9 O33 )4 ]⋅n H2 O (RE3+ =Tb3+ , x=1, y=2, n=36; RE3+ =Dy3+ , Ho3+ , Er3+ , Yb3+ , Y3+ , x=0, y=0, n=38; RE3+ = Tm3+ , x=1, y=0, n=38; Ser=serine; 2), and [H2 N(CH3 )2 ]6-2 x Na2+3 x REx H10-6 x+y [RE4 W8 O19 (H2 O)8 (OH)2 (Ser)4 (B-α-AsW9 O33 )4 ]⋅Cly ⋅n H2 O (RE3+ =Ce3+ , Pr3+ , x=1, y=0, n=65; RE3+ =Nd3+ , Sm3+ , x=0, y=0, n=65; RE3+ =Eu3+ , Gd3+ , x=1, y=2, n=45; 3) were synthesized with the participation of the organic solubilizers dimethylamine hydrochloride and l-serine and were structurally characterized. The use of different amounts of rare-earth salts results in the structural transformation from dimerization to tetramerization of types 1-3. Type 1 is a dimeric sandwich-type assembly of a dual-Ser-participating [RE2 W4 O10 (H2 O)8 (Ser)2 ]10+ entity sandwiched by two [B-α-AsW9 O33 ]9- moieties, whereas types 2 and 3 have a tetrameric square structure formed by four [B-α-AsW9 O33 ]9- moieties that anchor a dual/tetra- Ser-participating [RE4 W8 O19 (H2 O)10+y (OH)2 (Ser)2 ]20+ or [RE4 W8 O19 (H2 O)8 (OH)2 (Ser)4 ]20+ core. The solid-state luminescence properties and lifetime-decay behaviors of these compounds were investigated. The chromaticity coordinates, dominant wavelengths, color purities, and correlated color temperatures were also calculated.

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

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.

Unprecedented Selenium and Lanthanide Simultaneously Bridging Selenotungstate Aggregates Stabilized by Four Tetra-vacant Dawson-like {Se2W14} Units

In the presence of the larger [H2 N(CH3 )2 ]+ and K+ counter cations as structure-stabilizing agents, a class of unprecedented selenium and lanthanide (Ln) simultaneously bridging tetra-vacant Dawson-like selenotungstate aggregates [H2 N(CH3 )2 ]2 Na9 K2 H19 {[Ln4 W4 Se4 O22 (H2 O)5 ](Se2 W14 O52 )2 }2 ⋅60 H2 O [Ln=TbIII (1), DyIII (2), HoIII (3), ErIII (4), TmIII (5), YbIII (6)] have been obtained by the one-pot assembly reaction of Na2 WO4 ⋅2 H2 O, Ln(NO3 )3 ⋅6 H2 O, and Na2 SeO3 under moderately acidic aqueous conditions and the complexes were structurally characterized by elemental analyses, IR spectra, single-crystal X-ray diffraction, powder X-ray diffraction (PXRD), and thermogravimetric (TG) analyses. It should be noted that the appropriate molar ratio of Se/W is extremely important in the formation of 1-6 and can effectively ameliorate the yield of 1-6. Moreover, dimethylamine hydrochloride is also indispensable and plays a considerably important role in improving the solubility of Ln ions and stabilizing the structures of 1-6. The main polyoxoanion skeletons of 1-6 are constructed from two sandwich-type tetra-vacant Dawson-like {[Ln4 W4 Se4 O22 (H2 O)5 ](Se2 W14 O52 )2 }16- half-units linked through two W-O-Ln bridges. The sandwich-type half-unit comprises two tetra-vacant Dawson-like [Se2 W14 O52 ]12- fragments encapsulating a unique dodecanuclear Se-Ln-W [Ln4 W4 Se4 O22 (H2 O)5 ]8+ oxo cluster. Their solid-state visible and NIR fluorescent properties and lifetime decay behaviors were measured and their solid-state luminescent spectra mainly demonstrate the characteristic emission bands of Ln3+ ions. Moreover, the dominant wavelengths, the color purity, and correlated color temperatures of 1-5 have been also calculated. In addition, the luminous flux values of 1-5 are 2031, 6992, 3071, 921, and 477 lumen, respectively.

CCDC 1513004: Experimental Crystal Structure Determination

Related Article: Hai-Lou Li, Ya-Jie Liu, Jing-Lin Liu, Li-Juan Chen, Jun-Wei Zhao, Guo-Yu Yang|2017|Chem.-Eur.J.|23|2673|doi:10.1002/chem.201605070