Rare-Earth and Antimony-Oxo Clusters Simultaneously Connecting Antimonotungstates Comprising Divacant and Tetravacant Keggin Fragments

An Innovative SbIII-WVI-Cotemplated Antimonotungstate with Potential in Sensing Paroxetine Electrochemically

Advances in polyoxometalate (POM) self-assembly chemistry are always accompanied by new developments in molecular blocks. The exploration and discovery of uncommon building blocks offer great possibilities for generating unprecedented POM clusters. An intriguing SbIII-WVI-cotemplated antimonotungstate [H2N(CH3)2]11Na[SbW9O33]Er2(H2O)2Sb2[SbWVIW15O57]·22H2O (1) was synthesized, which comprises a classical trivacant Keggin [SbW9O33]9- ({SbW9}) fragment and an unclassical lacunary Dawson-like [SbWVIW15O57]15- ({SbWVIW15}) subunit. Notably, the Dawson-like {SbWVIW15} subunit is the first example of a [SbO3]3- and [WVIO6]6- mixed-heteroatom-directing POM segment. Hexacoordinated [WVIO6]6- can not only serve as the heteroatom function but its additional oxygen sites can also link to lanthanide, main-group metal, and transition-metal centers to form the innovative structure. {SbWVIW15} and {SbW9} subunits are joined by the heterometallic [Er2(H2O)2Sb2O17]22- cluster to give rise to an asymmetric sandwich-type architecture. To further realize its potential application in electrochemical sensing, a conductive 1@rGO composite was obtained by the electrochemical deposition of 1 with graphene oxide (GO). Using a 1@rGO-modified glassy carbon electrode as the working electrode, an electrochemical biosensor for detecting the antidepressant drug paroxetine (PRX) was successfully constructed. This work can provide a viable strategy for synthesizing mixed-heteroatom-directing POMs and demonstrates the application of POM-based materials for the electrochemical detection of drug molecules.

Cerium-Encapsulated SbIII-SeIV-Templating Polyoxotungstate for Electrochemically Sensing Human Multidrug Resistance Gene Segment

A tower-like SbIII-SeIV-templating polyoxotungstate [H2N(CH3)2]12Na7H3[Ce0.5/Na0.5(H2O)5]2[SbSe2W21O75]2·50H2O (1) was synthesized, whose skeleton is assembled from two prolonged lacunary Dawson [SbSe2W21O75]13- units and two [Ce0.5/Na0.5(H2O)5]2+ linkers. The uncommon [SbSe2W21O75]13- unit can be viewed as a combination of one [SeW6O21]2- group grafted onto a trivacant Dawson [SbSeW15O54]11- subunit. The conductive composite 1-Au@rGO containing 1, gold nanoparticles, and reduced graphene oxide (rGO) was conveniently prepared, using which the 1-Au@rGO-based electrochemical genosensor was constructed for detecting human multidrug resistance gene segment. This work enriches structural types of dual-heteroatom-inserted polyoxometalates and promotes the application of polyoxometalates in genosensors.

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

Three isostructural dl-serine covalently functionalized and multinuclear lanthanide (Ln³⁺)-embedded arsenotungstates, K₂[{As₄W₄₄O₁₃₇(OH)₁₈(H₂O)₂(dl-Ser)₂}{Ln₂(H₂O)₄(dl-Ser)}₂{Ln(H₂O)₇}₂]·70H₂O (Ln = Sm (1), Eu (2), and Gd (3); dl-Ser = C₃H₇NO₃), were prepared, where the centrosymmetric [{As₄W₄₄O₁₃₇(OH)₁₈(H₂O)₂(dl-Ser)₂}{Ln₂(H₂O)₄(dl-Ser)}₂]^8- polyanion consists of two {As₂W₁₉O₅₉(OH)₈(H₂O)}^6- fragments, integrated with a two-dl-serine-ornamented [W₆O₂₃(OH)₂(dl-Ser)₂{Ln₂(H₂O)₄}₂]^8- segment. In addition, the photochromic transformation of solid-state compounds 1-3 was observed from colorless to blue after a UV illumination of 4 min, and the decay process lasted as long as ∼20 h in the dark. The coloration kinetic half-life (t_1/2) values of compounds 1, 2, and 3 were calculated to be 0.597, 0.920, and 0.723 min, respectively. Furthermore, the luminescent properties and energy migration from arsenotungstates and organic chromophores to Sm³⁺ and Eu³⁺ ions in 1 and 2 have been intensively investigated. Further analysis manifests that 1 possesses an effective luminescent switchable behavior, triggered by its fast-responsive photochromism effect.

Oxalate-bridging NdIII-based arsenotungstate with multifunctional NIR-luminescence and magnetic properties

Oxalate bridged Nd-based arsenotungstate, K₁₄Na₆H₄[{(As₂W₁₉O₆₇(H₂O))Nd(H₂O)₂}₂(C₂O₄)]·64H₂O (1), was obtained from the reaction of K₁₄[As₂W₁₉O₆₇(H₂O)], oxalic acid, and NdCl₃·6H₂O in mildly acidic aqueous solution. The polyanion exhibits a dimeric structure in which the fully deprotonated oxalate ligands bridge two Nd^III cations and the arsenotungstate anions act as blocking ligands. The photoluminescence (PL) spectrum of 1 shows the characteristic emission peak of Nd^III in the near-infrared (NIR) region. However, the O → W charge-transfer transitions of arsenotungstate cannot effectively sensitize the emission of Nd^III cations as confirmed by the emission spectrum, due to the mismatch of the energy gap between ³T_1u → ¹A_1g (21.57 × 10³ cm^-1) of arsenotungstate components and ⁴F_3/2 → ⁴I_9/2 (11.43 × 10³ cm^-1) of Nd^III cations. Magnetic studies of 1 demonstrate its field-induced single-molecule magnet (SMM) behavior. Direct current magnetic susceptibility studies imply the weak ferromagnetic couplings present between the two neighboring Nd^III cations. In addition, the synergy between the coordination configuration of Nd^III cations and the intramolecular magnetic interaction was discussed.

Facile fabrication of Tb3+-functionalized COF mixed-matrix membrane as a highly sensitive platform for the sequential detection of oxolinic acid and nitrobenzene

A novel Tb³⁺-functionalized covalent organic framework-based polymer mixed-matrix membrane (Tb³⁺@COF MMM) has been successfully fabricated by incorporating the highly stable Tb³⁺@PI-COF as filler into polyvinylidene fluoride (PVDF) solution. Compared with pure COF membrane, MMM exhibits its good flexibility, processability and high detection sensitivity. The obtained Tb³⁺@COF-MMM (M) can be employed as a highly sensitive sensing platform for the sequential detection of oxolinic acid (OA) and nitrobenzene (NB) based on a "off-on-off" process. M has performed its great selectivity, high sensitivity, and low detection limit for detecting OA with "turn-on" mechanism. Moreover, owing to the good chemical stability and anti-interference of M sensor, it is prospective to efficiently detect residues of OA in serum or river water. After the detection of M-15 toward OA, the obtained fluorescent M-15/OA exhibits the rapid quenching, facile manipulation, cycling utility and low detection limits for sensing NB solution and vapor. This work has proposed a typical case of developing flexible Ln³⁺-functionalized COF-based polymer mixed-matrix membrane as a highly sensitive sensing platform for detecting OA and NB, simultaneously revealed the applied potentiality of M for monitoring animal health and environmental pollution.

3-Pyridylacetic-Based Lanthanide Complexes Exhibiting Magnetic Entropy Changes, Single-Molecule Magnet, and Fluorescence

Four complexes from lanthanides, 3-pyridylacetate, and 1,10-phenanthroline, formulated as [Ln2(3-PAA)2(μ-Cl)2(phen)4](ClO4)2 [Ln = Gd(1), Dy(2), Eu(3), Tb(4), 3-PAA = 3-pyridylacetic acid, phen = 1,10-phenanthroline], were obtained. The four compounds were characterized by IR spectra, thermogravimetric analyses, powder X-ray diffraction, and single-crystal X-ray diffraction. Compounds 1-4 are isomorphous, and they have a dinuclear structure. Magnetic studies reveal that 1 shows the magnetocaloric effect with -ΔS m max = 19.03 J kg-1 K-1 at 2 K for ΔH = 5 T, and 2 displays a field-induced single-molecule magnet with U eff = 19.02 K. The photoluminescent spectra of 3 and 4 exhibit strong characteristic emission, which demonstrate that the ligand-to-EuIII/TbIII energy transfer is efficient.

The postsynthetic renaissance of luminescent lanthanide ions on crystalline porous organic framework materials

A series of crystalline porous organic framework materials (CPOFs), such as metal-organic frameworks (MOFs), covalent organic frameworks (COFs) and hydrogen bonded organic frameworks (HOFs) have received extensive attentions due to...

Three Lanthanide-Functionalized Antimonotungstate Clusters with a {Sb4O4Ln3(H2O)8} Core: Syntheses, Structures, and Properties

Three lanthanide (Ln)-functionalized antimonotungstate (AT) clusters with a {Sb₄O₄Ln₃(H₂O)₈} core [H₂N(CH₃)₂]₁₄Na₈H₁₆[Sb₄O₄Ln₃(H₂O)₈W₂O₄(H₂O)₂(B-α-SbW₉O₃₃)₄]₂·87H₂O [Ln = Dy³⁺ (1), Ho³⁺ (2), Y³⁺ (3)] were synthesized in an acidic aqueous solution. Their molecular structural unit comprises two {Sb₄O₄Ln₃(H₂O)₈}-core-incorporated tetrameric [Sb₄O₄Ln₃(H₂O)₈W₂O₄(H₂O)₂ (B-α-SbW₉O₃₃)₄]^19- polyanionic units, each of which is assembled from an unprecedented [Sb₄O₄Ln₃(H₂O)₈W₂O₄(H₂O)₂]¹⁷⁺ heteroatom cluster surrounded by four trivacant [B-α-SbW₉O₃₃]^9- subunits. What is noteworthy is that a tetrahedral {Sb₄O₄} cluster is located at the center of the polyanionic unit, as far as we know, which is very infrequent in multi-Ln-functionalized polyoxometalate chemistry. Solid-state luminescent properties and energy migration of AT ligands to Dy³⁺ and Ho³⁺ cations in 1 and 2 have been intensively probed at ambient temperature. By varying the exciting wavelength from 250 to 450 nm, the emitting color could vary from blue to yellow for 1 and blue to green-yellow for 2, separately. In addition, high catalytic activities and good reusability of 2 as a heterogeneous catalyst for oxygenation reaction of sulfides have been systematically performed.

Nicotinic-Acid-Ornamented Tetrameric Rare-Earth-Substituted Phospho(III)tungstates with the Coexistence of Mixed Keggin/Dawson Building Blocks and Its Honeycomb Nanofilm for Detecting Toxins

A fascinating class of nicotinic-acid-ornamented tetrameric rare-earth (RE)-substituted phospho(III)tungstates [NH₂(CH₃)₂]₁₀Na₄H₈[RE₂(NA)(HNA)(H₂O)₆(W₂O₄)(β-H₂P₂^IIIW₁₃O₄₉)(α-HP^IIIW₉O₃₃)]₂·22 H₂O [RE = Nd³⁺ (1-Nd), Tb³⁺ (2-Tb), Dy³⁺ (3-Dy), Ho³⁺ (4-Ho), HNA = nicotinic acid] were isolated through a one-step reaction method of Na₂WO₄·2H₂O, H₃PO₃, HNA, NH₂(CH₃)₂·HCl, and RE(NO₃)·6H₂O. Of meticulous concern is that HPO₃^2- was used as a template to construct tetrameric RE-substituted phospho(III)tungstates including mixed heteropolyoxotungstate building blocks. Their hybrid polyoxoanions are composed of two symmetrical [RE₂(NA)(HNA)(H₂O)₆(W₂O₄)(β-H₂P₂^IIIW₁₃O₄₉)(α-HPW₉O₃₃)]^11- units linked by RE-O-W bonds. The symmetrical unit consists of one peculiar heterometal nicotinic-acid-ornamented [RE₂(NA)(HNA)(W₂O₄)]⁹⁺ cluster connecting a pentavacant Dawson-like [β-H₂P₂W₁₃O₄₉]^12- and a trivacant Keggin [α-HPW₉O₃₃]^8- subunits. Furthermore, dimethyldioctadecylammonium chloride (DMDODA·Cl) was used to combine with 1-Nd in the CHCl₃-H₂O system through electrostatic interactions, leading to the 1-Nd@DMDODA composite material. The honeycomb-patterned film of the 1-Nd @DMDODA composite material was successfully constructed by using the breath figure method on a glassy carbon electrode, which can offer abundant binding sites to Au nanoparticles (nano-Au). Ulteriorly, Au-functionalized 1-Nd@DMDODA-modified electrode was utilized as an electrochemical sensor to detect ochratoxin A, showing a good detection limit of 1.19 pM.

Organoamine-Directed Assembly of 5p-4f Heterometallic Cluster Substituted Polyoxometalates: Luminescence and Proton Conduction Properties

The assembly of heterometallic cluster substituted polyoxometalates (POMs) remains a great challenge for inorganic synthetic chemistry up to now. Herein, a series of 5p-4f heterometallic cluster substituted POMs were successfully isolated by a facile one-step hydrothermal reaction method, namely H₁₇(H₂en)₃[Sb^III₉Sb^VLn₃O₁₄(H₂O)₃][(SbW₉O₃₃)₃(PW₉O₃₄)]·28H₂O(1-Ln, Ln = Ce, Sm, Eu, Gd, Tb, Dy) (en = ethylenediamine). Interestingly, by replacing en with imidazole, another series of 5p-4f heterometallic cluster substituted POMs H₁₃(HIm)₄K₂Na₄(H₂O)₉[Sb^III₉Sb^VLn₃O₁₄(H₂O)₃][(SbW₉O₃₃)₃(PW₉O₃₄)]·26H₂O (2-Ln, Ln = Sm, Eu, Gd, Tb, Dy, Im = imidazole) were obtained. Structural analyses indicate that both 1-Ln and 2-Ln are made up of an unprecedented 5p-4f heterometallic {Sb₁₀Ln₃O₁₄(H₂O)₃} cluster stabilized simultaneously by mixed trilacunary heteropolyanions including {A-α-PW₉O₃₄} and {B-α-SbW₉O₃₃}. Impedance measurements indicate that both compounds exhibit different proton conduction properties, and the conductivity of 2 can reach up to 1.64 × 10^-2 S cm^-1 at 85 °C under 98% relative humidity. Moreover, the fluorescence emission behaviors of both compounds have been studied.

Multinuclear Lanthanide-Implanted Tetrameric Dawson-Type Phosphotungstates with Switchable Luminescence Behaviors Induced by Fast Photochromism

A series of benzoate-decorated lanthanide (Ln)-containing tetrameric Dawson-type phosphotungstates [N(CH₃)₄]₆H₂₀[{(P₂W₁₇O₆₁)Ln(H₂O)₃Ln(C₆H₅COO)(H₂O)₆]}{[(P₂W₁₇O₆₁)Ln(H₂O)₃}]₂Cl₂·98H₂O [Ln = Sm (1), Eu (2), and Gd (3)] were made using a facile one-step assembly strategy and characterized by several techniques. Notably, the Ln-containing tetrameric Dawson-type polyoxoanions [{(P₂W₁₇O₆₁)Ln(H₂O)₃Ln(C₆H₅COO)(H₂O)₆]}{[(P₂W₁₇O₆₁)Ln(H₂O)₃}]₂^24- are all established by four monolacunary Dawson-type [P₂W₁₇O₆₁]^10- segments, encapsulating a Ln³⁺ ion with two benzoates coordinating to the Ln³⁺ ions. 1-3 exhibit reversible photochromism, which can change from intrinsic white to blue for 6 min upon UV irradiation, and their colors gradually recover for 30 h in the dark. The solid-state photoluminescence spectra of 1 and 2 display characteristic emissions of Ln components based on 4f-4f transitions. Time-resolved emission spectra of 1 and 2 were also measured to authenticate the energy transfer from the phosphotungstate and organic chromophores to Eu³⁺. In particular, 1 shows an effectively switchable luminescence behavior induced by its fast photochromism.

Tricarboxylic-Ligand-Decorated Lanthanoid-Inserted Heteropolyoxometalates Built by Mixed-Heteroatom-Directing Polyoxotungstate Units: Syntheses, Structures, and Electrochemical Sensing for 17β-Estradiol

Organic-inorganic hybrid metal-oxide clusters have been pursued for many years, benefiting from their abundant structures and prominent performances. Upon our exploration, a family of unusual mixed-heteroatom (Sb^III, P^III)-directing lanthanoid (Ln)-inserted heteropolyoxotungstates (Ln-HPOTs), [(CH₃)₂NH₂]₂Na₇H₃[Ln₄(HP^III)W₈(H₂O)₁₂(H₂ptca)₂O₂₈][Sb^IIIW₉O₃₃]₂·27H₂O [Ln = Ce³⁺ (1), La³⁺ (2), Pr³⁺ (3)], functionalized by 1,2,3-propanetricarboxylic acid (H₃ptca) was achieved. The intriguing trimeric [Ln₄(HP^III)W₈(H₂O)₁₂(H₂ptca)₂O₂₈][Sb^IIIW₉O₃₃]₂^12- polyanion was established by two trivacant [B-α-Sb^IIIW₉O₃₃]^9- segments mounted on both sides and one rare [HP^IIIW₄O₁₈]^8- segment at the bottom, which are bridged via an organic-inorganic hybrid [W₄Ln₄(H₂O)₁₂O₁₀(H₂ptca)₂]¹⁴⁺ central moiety. Such Ln-HPOTs involving dual-heteroatom-directing mixed building blocks, and even simultaneously modified by tricarboxylic ligands, are rather unseen in polyoxometalate chemistry. Moreover, the detection of 17β-estradiol through a 1-based electrochemical biosensor has been explored, demonstrating a low detection limit (7.08 × 10^-14 M) and considerable stability.

Sandwich-Type Uranyl Phosphate-Polyoxometalate Cluster Exhibiting Strong Luminescence

A pure inorganic uranyl phosphate-polyoxometalate of Na₁₇{Na@[(SbW₉O₃₃)₂(UO₂)₆(PO₃OH)₆]}·xH₂O (abbreviated as Na@U₆P₆, with x ≈ 46) featuring a sandwich-type structure was prepared using Keggin-type trilacunary [α-B-SbW₉O₃₃]^9- units as building blocks, which were formed in situ by SbCl₃ and Na₂WO₄·2H₂O. Crystal structural analysis showed that six UO₂²⁺ cations and six PO₃OH^2- anions generated a wheel-like cluster unit with a Na⁺ center ([Na@(UO₂)₆(PO₃OH)₆]⁺) that is stabilized by two [α-B-SbW₉O₃₃]^9- units. Na@U₆P₆ displayed a solid-state photoluminescence quantum yield of 33% at 300 K. The temperature-dependent fluorescence emission spectra showed that Na@U₆P₆ has temperature-sensitive fluorescence in which its emission intensity decreased by 77% as the temperature increased from 200 to 300 K. These results suggest that such uranyl phosphate-polyoxometalate clusters could serve as potential temperature-sensitive molecular materials.

{HPO3} and {WO4} Simultaneously Induce the Assembly of Tri-Ln(III)-Incorporated Antimonotungstates and Their Photoluminescence Behaviors

A double template agent strategy has been adopted to prepare a group of triacetate-adorned tri-Ln(III)-incorporated trimeric antimonotungstates (AMTs) K₃Na₂₁H[Ln₃(CH₃COO)₃(HPO₃)(WO₄)][B-α-SbW₉O₃₃]₃·36H₂O [Ln = Eu³⁺ (1), Dy³⁺ (2), Ho³⁺ (3), or Er³⁺ (4)] in a CH₃COOH-CH₃COONa buffer system. Therein, H₃PO₃ and Na₂WO₄·2H₂O have been, respectively, transformed into the capped {HPO₃} and {WO₄} tetrahedra during the assembly process, which are situated at the center of polyoxoanions of 1-4 and simultaneously perform as structure-directing templates to induce the assembly of 1-4. The hexahedral configuration supramolecular stacking is the same as the shape of a crystal of 1, which illustrates that the supramolecular stacking mode plays a significant role in forming the crystal shape of 1-4. Under the Ln³⁺ f-f excitation, the photoluminescence behaviors involving the emission spectrograms and fluorescence decay curves of 1-4 were systematically researched. The modulation of the excitation wavelength has realized the emission color tuning from blue to red, blue to green, blue to yellow, and green to yellow for 1-4. On the basis of the excitation of O → W charge transfer (OWCT), the energy-transfer procedure from AMT units to Eu³⁺ centers in 1 is mainly accomplished in the form of energy reabsorption. This work proposes a typical case for the construction of a new type of AMT clusters by using the double template agent strategy and confirms the great potential of Ln-containing AMTs in optic applications.

A turn-on fluorescence sensing strategy for rapid detection of flumequine in water environments using covalent-coordination functionalized MOFs

With high output and large use of antibiotics in the process of aquaculture, pollution caused by antibiotics in water environments is becoming a thorny problem, and its ecological risk has aroused widespread concern.

A new family of dinuclear lanthanide complexes exhibiting luminescence, magnetic entropy changes and single molecule magnet behaviors

Four isomorphic and dinuclear lanthanide complexes were synthesized. Complexes Eu^III and Tb^III exhibit strong emissions, while Gd^III shows the magnetocaloric effect and Dy^III displays a single-molecule magnet.

A trimeric tri-Tb3+ including antimonotungstate and its Eu3+/Tb3+/Dy3+/Gd3+-codoped species with luminescence properties

A trimeric tri-Tb3+-including antimonotungstate (AMT) hybrid Na17{(WO4)[Tb(H2O)(Ac)(B-α-SbW9O31(OH)2)]3}·50H2O (Tb3W28) was successfully synthesized, in which the capped tetrahedral {WO4} group plays a significant template role in directing the aggregation of three [B-α-SbW9O33]9- fragments and three Tb3+ ions. Eu3+/Tb3+/Dy3+/Gd3+-codoped AMT materials based on Tb3W28 were firstly prepared and their luminescence properties were investigated. The red emitter Eu3+, yellow emitter Dy3+, and nonluminous Gd3+ ions were codoped into Tb3W28 to substitute Tb3+ ions for investigating the energy transfer (ET) mechanism among Eu3+, Tb3+, and Dy3+ ions. Upon the 6H15/2 → 4I13/2 excitation at 389 nm of the Dy3+ ion, the ET1 mechanism (Dy3+ → Tb3+) was confirmed as a non-radiative dipole-dipole interaction. Under the 7F6 → 5L10 excitation at 370 nm of the Tb3+ ion, the ET2 mechanism (Tb3+ → Eu3+) was identified as a non-radiative quadrupole-quadrupole interaction. Under excitation at 389 nm, the two-step successive Dy3+ → Tb3+ → Eu3+ ET3 process was proved in Dy1.2Tb3zEu0.03Gd1.77-3zW28. Through changing the excitation wavelengths, the emission color of Dy1.2Tb1.2Eu0.03Gd0.57W28 can vary from blue to yellow, in which a near-white-light emission case was observed upon excitation at 378 nm. This work not only provides a systematic ET mechanism study of hetero-Ln-codoped AMTs, but also offers some useful guidance for designing novel performance-oriented Ln-codoped polyoxometalate-based materials.

H-shaped oxalate-bridging lanthanoid-incorporated arsenotungstates

A series of oxalate-bridging di-Ln³⁺-incorporated H-shaped polyoxometalates were synthesized and their stability in solution was evidenced by Raman spectroscopy.

Ionic strength effect on regulating the synthetic assembly of polyoxometalate clusters with slow magnetic relaxation behavior

Three novel polyoxometalate (POM) clusters of K10Na10[Dy3(H2O)6Ni(H2O)(W3O11)(B-α-SbW9O33)3]·(H2O)45 (1), (NH4)5K4Na8[Dy3(H2O)6SbV(H2O)(W3O11)(B-α-SbW9O33)3]·(H2O)50 (2), and (NH4)9Na[Ni2(H2O)6(WO2)2(B-β-SbW9O33)2]·(H2O)24 (3) were successfully obtained using the same precursor under different ionic strength conditions. Structural analysis showed that compounds 1-3 possess discrepant structural characteristics in 1 M KCl, 1 M NH4Cl, and saturated NH4Cl, respectively. Among them, 2 is the first reported lanthanide cluster including both Sb3+ and Sb5+ in POM derivatives. Furthermore, the analysis of ac magnetic data proved that 1 and 2 embodied dramatic field-induced slow magnetic relaxation, and the effective barrier of 2 was estimated as Ueff/KB = 21.10 K based on the Orbach process. It was found that the structure and magnetic properties of POM materials can be regulated using an effective and satisfactory ionic strength-controlled strategy.

Polyoxometalate-based room-temperature phosphorescent materials induced by anion–π interactions

A series of polyoxometalate-based host–guest materials emit strong red room-temperature phosphorescence attributed to intermolecular charge-transfer states which was caused by unorthodox anion–π interactions.

Syntheses, Crystal Structure, Electrocatalytic, and Magnetic Properties of the Monolanthanide-Containing Germanotungstates [Ln(H2O) n GeW11O39]5- (Ln = Dy, Er, n = 4,3)

Two monolanthanide-containing polyanions based on monolacunary Keggin germanotungstates [Ln(H2O) n GeW11O39]5- (Ln = Dy, Er, n = 4,3) have been synthesized in simple one-pot synthetic procedure and compositionally characterized in solid state by single-crystal X-ray diffraction, powder X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, and elemental analysis. Electronic absorption and emission spectra of the title compounds in solution were also studied. The [DyIII(H2O)4GeW11O39]5- Keggin POM exhibits a slow relaxation of magnetization. The cyclic voltammetry measurements and mass spectrometry were carried out to check the stability of the compounds in solution. Both polyanions prove efficient in the electrocatalytic reduction of nitrite. To our knowledge, this observation establishes the first example of electrocatalysis of nitrite reduction by all inorganic monolanthanide-containing germanotungstates family.

Double-Oxalate-Bridging Tetralanthanide Containing Divacant Lindqvist Isopolytungstates with an Energy Transfer Mechanism and Luminous Color Adjustablility Through Eu3+/Tb3+ Codoping

A double-oxalate-bridging tetra-Gd³⁺ containing divacant Lindqvist dimeric isopolytungtate Na₁₀[Gd₂(C₂O₄)(H₂O)₄(OH)W₄O₁₆]₂·30H₂O (Gd₄W₈) was obtained based on the reaction of Na₂WO₄·2H₂O, H₂C₂O₄, and GdCl₃ in aqueous solution. Its dimeric polyoxoanion is established by two divacant Lindqvist [W₄O₁₆]^8- segments connected by a rectangular tetra-nuclearity [Gd₄(C₂O₄)₂(H₂O)₈(OH)₂]⁶⁺ cluster. Notably, neighboring trinuclear [Na₃O₄(H₂O)₁₁]^5- clusters are interconnected to construct a picturesque 1-D sinusoidal Na-O cluster chain. The most outstanding characteristic is that 1-D sinusoidal Na-O cluster chains combine [Gd₂(C₂O₄)(H₂O)₄(OH)W₄O₁₆]₂^10- polyoxoanions together, giving rise to an intriguing 3-D extended porous framework. The red emitter Eu³⁺ ions and green emitter Tb³⁺ ions are first codoped into Gd₄W₈ to substitute Gd³⁺ ions for the exploration of the energy transfer (ET) mechanism between Eu³⁺ and Tb³⁺ ions and the color-tunable PL property in the isopolytungtate system. The PL emission spectra and decay lifetime measurements of the Eu³⁺/Tb³⁺ codoped Gd₄W₈ system illustrate that under excitation at 370 nm, Tb³⁺ ions can transfer energy to Eu³⁺ ions. When the molar concentration of Tb³⁺ ions is fixed at 0.9 and that of the Eu³⁺ ions gradually increases from 0.01 to 0.08, the calculated ET efficiency (η_ET) from Tb³⁺ to Eu³⁺ ions increases from 7.9% for Gd_0.36Tb_3.6Eu_0.04W₈ to 67.3% for Gd_0.08Tb_3.6Eu_0.32W₈. The energy transfer mechanism (Tb³⁺ → Eu³⁺) is a nonradiative dipole-dipole interaction. Furthermore, upon excitation at 370 nm, Eu₄W₈ and Tb₄W₈ show visible red- and green-emitting lights, respectively. When codoping trace amounts of Eu³⁺ ions in Tb₄W₈, under excitation at 370 nm, Tb_3.92Eu_0.08W₈ displays near white-light emission.