Three types of serine-decorated rare- earth-containing arsenotungstate [H N(CH ) ] NaH[RE W O (H O) (Ser) (B-α-AsW O ) ]⋅30 H O (RE =Eu , Gd , Tb , Dy , Ho , Er , Tm , Yb , and Y ; 1), [H N(CH ) ] Na RE H [RE W O (H O) (OH) (Ser) (B-α-AsW O ) ]⋅n H O (RE =Tb , x=1, y=2, n=36; RE =Dy , Ho , Er , Yb , Y , x=0, y=0, n=38; RE = Tm , x=1, y=0, n=38; Ser=serine; 2), and [H N(CH ) ] Na RE H [RE W O (H O) (OH) (Ser) (B-α-AsW O ) ]⋅Cl ⋅n H O (RE =Ce , Pr , x=1, y=0, n=65; RE =Nd , Sm , x=0, y=0, n=65; RE =Eu , Gd , 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 [RE W O (H O) (Ser) ] entity sandwiched by two [B-α-AsW O ] moieties, whereas types 2 and 3 have a tetrameric square structure formed by four [B-α-AsW O ] moieties that anchor a dual/tetra- Ser-participating [RE W O (H O) (OH) (Ser) ] or [RE W O (H O) (OH) (Ser) ] 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.

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.

A double-oxalate-bridging tetra-Gd 3+ containing divacant Lindqvist dimeric isopolytungtate Na 10 [Gd 2 (C 2 O 4 )(H 2 O) 4 (OH)W 4 O 16 ] 2 •30H 2 O (Gd 4 W 8 ) was obtained based on the reaction of Na 2 WO 4 •2H 2 O, H 2 C 2 O 4 , and GdCl 3 in aqueous solution. Its dimeric polyoxoanion is established by two divacant Lindqvist [W 4 O 16 ] 8− segments c o n n e c t e d b y a r e c t a n g u l a r t e t r a -n u c l e a r i t y [Gd 4 (C 2 O 4 ) 2 (H 2 O) 8 (OH) 2 ] 6+ cluster. Notably, neighboring trinuclear10− polyoxoanions together, giving rise to an intriguing 3-D extended porous framework. The red emitter Eu 3+ ions and green emitter Tb 3+ ions are first codoped into Gd 4 W 8 to substitute Gd 3+ ions for the exploration of the energy transfer (ET) mechanism between Eu 3+ and Tb 3+ ions and the color-tunable PL property in the isopolytungtate system. The PL emission spectra and decay lifetime measurements of the Eu 3+ /Tb 3+ codoped Gd 4 W 8 system illustrate that under excitation at 370 nm, Tb 3+ ions can transfer energy to Eu 3+ ions. When the molar concentration of Tb 3+ ions is fixed at 0.9 and that of the Eu 3+ ions gradually increases from 0.01 to 0.08, the calculated ET efficiency (η ET ) from Tb 3+ to Eu 3+ ions increases from 7.9% for Gd 0.36 Tb 3.6 Eu 0.04 W 8 to 67.3% for Gd 0.08 Tb 3.6 Eu 0.32 W 8 . The energy transfer mechanism (Tb 3+ → Eu 3+ ) is a nonradiative dipole−dipole interaction. Furthermore, upon excitation at 370 nm, Eu 4 W 8 and Tb 4 W 8 show visible red-and green-emitting lights, respectively. When codoping trace amounts of Eu 3+ ions in Tb 4 W 8 , under excitation at 370 nm, Tb 3.92 Eu 0.08 W 8 displays near white-light emission.

A novel mixed-valence, ring-shaped multinuclear Mn-containing polyoxometalate, [H 2 N(CH 3 ) 2 ] 15 NaH 8 -[Mn III 3 Mn IV (μ 3 -O) 3 (OAc)PO 4 (B-α-PW 9 O 34 )] 4 • 36H 2 O (1) was made and systematically characterized using various spectroscopic and computational techniques. Its polyoxoanion can be described as a tetramer made of four [Mn III 3 Mn IV (μ 3 -O) 3 (OAc) (B-α-PW 9 O 34 )] 3− ({Mn III 3 Mn IV (PW 9 )}) clusters and four PO 4 linkers. Significantly, this structurally new complex 1 can efficiently catalyze hydrogen evolution with 23 μmol H 2 gas after 12 h of visible-light irradiation using a three-component system. We propose a possible catalytic hydrogenevolving mechanism based on both experimental results and density functional theory (DFT) calculations.