dl-Serine Covalently Ornamented and Ln3+-Incorporated Arsenotungstates with Fast-Responsive Photochromic and Photoinduced Luminescent Switchable Behaviors

Tetra-Ln3+-Implanted Tellurotungstates Covalently Modified by dl-Malic Acid: Proton Conduction and Photochromic Properties

Three unique dl-malic acid covalently modified tetra-Ln3+-implanted tellurotungstates [H2(CH3)2]9NaH9[Ln4(H2O)14W6O13(OH)5(Mal)2(B-α-TeW9O33)4]·48H2O [Ln = La3+ (1), Ce3+ (2), Pr3+ (3); H3Mal = dl-malic acid] were fabricated by reacting Na2TeO3, Na2WO4·2H2O, Mal, and LnCl3·6H2O with dimethylamine hydrochloride in an aqueous solution. The most prominent architectural feature of these compounds is the covalent connection mode of an organic ligand and a polyoxometallate backbone, which is relatively rare in the realm of polyoxotungstates. The tetrameric polyanion can be deemed as four [TeW9O33]8- fragments fused together via an intriguing hexanuclearity [W6O13(OH)5(Mal)2Ln4(H2O)14]13+ cluster. Impedance measurements manifest that all three complexes display splendid proton conduction properties, with an exceptional conductivity for 2 up to 2.48 × 10-2 S·cm-1 under 85 °C and 95% relative humidity. Moreover, compounds 1 and 3 exhibited fast reversible photochromic properties with allochroic half-life periods t1/2 of 1.046 and 0.544 min, respectively.

Recent advances in lanthanide-based POMs for photoluminescent applications

Since the first formation of the famous "Peacock-Weakley" anions [Ln(W5O18)2]8/9-, a steady stream of breakthroughs have been made in the chemistry of multitalented lanthanide (Ln)-based polyoxometalates (POMs) for their potentially desirable properties. In particular, LnIII ions are generally recognised as the "vitamins of the modern industry" owing to their ability to cover a wide emission range, endowing Ln-based POMs with great potential for versatile and diverse luminescence-related applications. In this frontier, we discuss the synthesis strategies and intramolecular energy transfer in Ln-based POM derivatives. Then, the progressive improvements achieved with Ln-based POMs in photoluminescence applications are highlighted, focusing mainly on luminescent and fluorescent probes. Finally, the challenges for Ln-based POM materials for photoluminescence applications are discussed.

Two Tetra-Nuclear Ln-Substituted Prazine Dicarboxylic Acid-Functionalized Selenotungstates with Catalytic Oxidation of Thioether Properties

Two two-dimensional Ln-substituted prazine dicarboxylic acid-functionalized selenotungstates Na3H9[(H2N(CH3)2]2{(Se4W27O100)[Ln4(H2O)8(Hpzdc)2(pzdc)]}·26H2O [Ln = Nd (1) and Ce (2)]; H2pzdc = 2,3-pyrazine dicarboxylic acid) have been synthesized by one-pot self-assembly strategy, in which the basic polyanion [Se4W27O100]22-was composed of two [SeW8O31]10- fragments, a [SeW9O33]8- segment and an intriguing {SeO} group, simultaneously tetra-nuclear Ln3+ ions with H2pzdc pendants were embedded. Compounds 1 and 2 showed excellent catalytic oxidation of thioether properties within a short time (20 min) with high 100% conversion and 98.9% selectivity. In addition, the pioneering Ln-substituted selenotungstates were used as catalysts to degrade sulfur mustard simulant 2-chloroethyl ethyl sulfide at room temperature with 99% conversion and 100% selectivity. The chemical kinetic experiment studies revealed that the catalytic reaction was in compliance with the first-order reaction, and the kinetic half-life (t1/2) values were 3.814 and 3.849 min, respectively.

A d-Methionine-Bonded Nanosized Heteropolyoxotungstate with Photocoloration

A d-methionine-bonded nanosized arsenotungstate, Ba9K10H6[{As2W19O67(H2O)}2{AsW9O33}2{W3O6(H2O)(d-Met)}2{W2O4(OH)(d-Met)}]·60H2O [1; d-Met = d-methionine (C5H11NO2S)], is constructed without the use of lanthanide ions. The polyanion of 1 contains two {As2W19O67(H2O)}14- building blocks and two {B-β-AsW9O33}9- subunits, integrated together with a {W2O4(OH)(d-Met)}2+ and two {W3O6(H2O)(d-Met)}5+ subclusters. Interestingly, 1 displays a highly reversible photocoloration property with a half-life (t1/2) time measured as about 0.793 min.

Discovery and Isolation of Two Arsenotungastate Species: [As4W48O168]36- and [As2W21O77(H2O)3]22

Two novel arsenotungstate species, [As₄W₄₈O₁₆₈]^36- (1a) and [As₂W₂₁O₇₇(H₂O)₃]^22- (2a), have been successfully isolated under a one-pot synthetic method. 1a is the second largest arsenotungstate cluster and is constructed from four {AsW₁₂} clusters combined together. 2a can be described as lacunary sites of {As₂W₁₉} filled by {W₂O₈} units. Compounds 1 and 2 exhibit proton conductivity properties, and the conductivity value of 1 is 5.0 × 10^-3 S cm^-1 at 98% relative humidity and 75 °C. This work proves that the lattice water molecules and polyoxoanions can participate in the formation of a hydrogen bond, acting as effective pathway for intermolecular proton conduction.