Three Types of Lanthanide-Containing Polyoxoniobates and Their Luminescence Properties

Fourteen lanthanide (Ln)-containing hetero selenato-phosphato-peroxopolyoxoniobates in three series: (1) Cs₂{[Ln(H₂O)₄][H₄P₂Se₂Nb₆(O₂)₆O₂₂]}₂·nH₂O [Ln = Ce (I-Ce), Pr (I-Pr), Sm (I-Sm), Eu (I-Eu), Gd (I-Gd); I-Ce, I-Pr, I-Eu, I-Gd n = 12; I-Sm n = 16]; (2) Cs₂K₃{[Ln(H₂O)₆][H_2.5P₂Se₂Nb₆(O₂)₆O₂₂]}₂·nH₂O [Ln = Dy (II-Dy), Tm (II-Tm), Yb (II-Yb), Lu (II-Lu); II-Dy n = 14; II-Tm n = 24; II-Yb, II-Lu n = 13]; (3) Cs₅K₂H_m{[Ln(H₂O)₆][P₂Se₂Nb₆(O₂)₆O₂₂]}₂{[Ln_x(H₂O)_y]₂[P₂Se₂Nb₆(O₂)₆O₂₂]}·nH₂O [Ln = Ho (III-Ho), Er (III-Er), Tm (III-Tm), Yb (III-Yb), Lu (III-Lu), III-Ho-III-Yb m = 5, x = 1; y = 5; III-Lu m = 6.5; x = 0.75; y = 4; III-Ho-III-Tm n = 19, III-Yb n = 34; III-Lu n = 31], have been isolated by a one-pot reaction and structurally characterized by various physical and chemical analyses. These compounds represent the first group of Ln-functionalized polyoxoniobates with mixed heteroatoms. In addition, the photoluminescence properties of compounds I-Sm, I-Eu, and II-Dy were measured, and the time-resolved emission spectra showed that the {P₂Se₂Nb₆} segment contributed to the energy transfer from the polyoxoniobate units to the Ln³⁺ center, which effectively promoted the emission of the Ln³⁺ center.

Syntheses, characterization and properties of two new dodeca-niobates presenting unprecedented features

Two new dodeca-niobate materials, K3[Nb2O2][H7SiNb12O40]·16H2O (1) and [Cu(en)2]9[(VNb12V1.69Nb0.31O42en0.31)2]·20.69H2O (2) (en = ethylenediamine), have been obtained under hydrothermal conditions and characterized by IR, UV-Vis, XRD, and single crystal X-ray diffraction analysis. Single crystal X-ray analysis reveals that compound 1 presents a reasonable bridging layer structure model and that K plays a great role in the three-dimensional structure. Compound 2 is the first capped Keggin POM with organic ligand chelating the capping atom. The photocatalytic hydrogen evolution and styrene epoxidation catalytic properties of the two compounds were also assessed. Additionally, compound 1 is also a good photocatalyst to degrade RhB.

Boronic acid derivatized lanthanide–polyoxometalates with novel B–OH–Ln and B–O–Nb bridges

Boronic acid derivatized Ln–POMs were synthesized by pH-controlled formation of B–OH–Ln and B–O–Nb bridges.

Niobium uptake by a [P8W48O184]40−macrocyclic polyanion

Incorporation of Nb into the [P₈W₄₈O₁₈₄]⁴⁰⁻anionic macrocyclic cavitand leads to formation of new Nb–W POMs. Inclusion of up to five {NbO(H₂O)}³⁺groups was observed. Solution speciation of the Nb-encapsulating macrocycles was studied by HPLC-ICP-AES and SAXS.

Synthesis, characterization, and photoluminescence properties of three two-dimensional lanthanide-containing Dawson-type polyoxometalates

Three isostructural lanthanide-containing polyoxometalates with 2D network architectures were successfully obtained under hydrothermal conditions.

Rare-Earth-Incorporated Tellurotungstate Hybrids Functionalized by 2-Picolinic Acid Ligands: Syntheses, Structures, and Properties

A series of organic-inorganic rare-earth-incorporated tellurotungstate hybrids, Na₄[RE₂(H₂O)₄(pica)₂W₂O₅][(RE(H₂O)W₂(Hpica)₂O₄)(B-β-TeW₈O₃₀H₂)₂]₂·38H₂O (RE = La^III (1), Ce^III (2), Nd^III (3), Sm^III (4), Eu^III (5); Hpica = 2-picolinic acid), were prepared via a one-step assembly reaction of Na₂WO₄·2H₂O, RE(NO₃)₃·6H₂O, K₂TeO₃, Hpica, and triethylamine (tea). Notably, the solubilization of tea toward Hpica and the solubilization of Hpica toward RE cations in the reaction system play an important role in the formation of 1-5. The most significant feature of 1-5 consists of an intriguing tetrameric [RE₂(H₂O)₄(pica)₂W₂O₅][(RE(H₂O)W₂(Hpica)₂O₄)(B-β-TeW₈O₃₀H₂)₂]₂^4- polyoxoanion constructed from two tetravacant Keggin sandwich-type [(RE(H₂O)W₂(Hpica)₂O₄)(B-β-TeW₈O₃₀H₂)₂]^5- entities linked by a RE-W-Hpica {RE₂(H₂O)₄(pica)₂W₂O₅}⁶⁺ cluster, in which Hpica ligands not only play a key bridging role in linking RE and W centers by carboxylic groups in an irregular N-O-RE-O-W-O six-membered-ring motif but also can directly chelate with W centers via N and O atoms in a stable N-O-C-O-W five-membered-ring fashion. 1-5 represent rare organic-inorganic hybrid RE-substituted tellurotungstates. Moreover, the solid-state photoluminescence properties of 3-5 have been deeply investigated, and these compounds exhibit the characteristic emission stemming from intra-4f transitions of RE ions. The energy transfer of the O → W transitions sensitizing the emission of Sm^III centers in 4 is convincingly proved by time-resolved emission spectra (TRES); the increase in the strongest typical emission of Sm^III ions at a decay time of 17 μs is accompanied by the decline of O → W emission, and the CIE 1931 diagram was obtained from the corresponding TRES. Furthermore, a comparison of the luminescence behaviors of 5 in the solid state and in solution reveals the structural skeletal integrity of 5 in solution and a shorter decay lifetime in the solution caused by the high-frequency O-H oscillators.

Two mixed-addenda Nb/W polyoxometalate-based hybrid compounds containing multicopper units: synthesis, structures, and electrochemical and magnetic properties

Two Nb/W mixed-addenda polyoxometalate-based hybrid compounds were synthesized. Their structures and properties were studied.

Tellurotungstate-Based Organotin-Rare-Earth Heterometallic Hybrids with Four Organic Components

A family of unprecedented tellurotungstate-based organotin-rare-earth (RE) heterometallic hybrids [H₂N(CH₃)₂]₆H₁₂Na₂ {[Sn(CH₃)W₂O₄(IN)][(B-α-TeW₈O₃₁)RE(H₂O) (Ac)]₂}₂·25H₂O [RE = Ce^III (1), Pr^III (2), Nd^III (3), Sm^III (4), Eu^III (5), Gd^III (6), Tb^III (7); HIN = isonicotinic acid, HAc = acetic acid] were synthesized and characterized by elemental analyses, IR spectra, UV spectra, thermogravimetric analyses, powder X-ray diffraction, and single-crystal X-ray diffraction. The polyoxoanionic skeletons {[Sn(CH₃)W₂O₄(IN)][(B-α-TeW₈O₃₁)RE(H₂O) (Ac)]₂}₂^20- of 1-7 are constructed from two symmetrical units {[Sn(CH₃)W₂O₄(IN)][(B-α-TeW₈O₃₁)RE(H₂O) (Ac)]₂}^10- linked by two acetate connectors, which not only represent the first inorganic-organic hybrid RE-substituted tellurotungstates involving three different organic ligands, but also stand for the first samples of organotin-RE heterometallic polyoxometalate derivatives. The solid-state luminescent emission properties of 2-5 mainly display the characteristic emission bands of RE^III cations, whereas during the emission procedure of 7, [B-α-TeW₈O₃₁]^10- segments make a nonignorable contribution to the PL behavior of 7 accompanying by the occurrence of the intramolecular energy transfer from O→W LMCT energy to Tb³⁺ centers. Furthermore, 4@CTAB composites with peanutlike and honeycombed morphologies were prepared by a surfactant cetyltrimethylammonium bromide (CTAB). The time-resolved emission spectra of the 4@CTAB composite with CTAB/4 = 0.033/0.05 consolidate the energy transfer from CTAB to RE^III centers. Variable-temperature magnetic susceptibility measurements for 2, 3, and 4 were performed.

A luminescent polyoxoniobate lanthanide derivative {Eu3(H2O)9[Nb48O138(H2O)6]}27−

An Eu-containing polyoxoniobate (CN₃H₆)₇K₃H₁₇{Eu₃(H₂O)₉Nb₄₈O₁₃₈(H₂O)₆}·40H₂O is obtained under the protection of citric acid, which is a triangular cylindrical entity and displays red emission.

Two nanoscale Nb containing polyoxometalates based on {P2W15Nb3O62} clusters and chromium cations

We have introduced mixed-addenda Nb/W polyoxometalates as a new class of materials for lithium-ion batteries and demonstrated their capability as anode materials with good cycling stability.

Self-assembly of [PNbxW12−xO40]n− Keggin anions – a simple way to mixed Nb–W polyoxometalates

This paper summarizes preparations of mixed phosphoniobotungstates [PNb_xW_12−xO₄₀]^(3+x)− (x = 1–3) based on two different ways: incorporation of Nb into pre-existing lacunary-type phosphotungstates and self-assembly reactions.

An unprecedented 3D architecture based on a Nb/W mixed-addendum polyoxometalate and lanthanide–organic complex: synthesis, crystal structure and properties

For the first time, a 3D framework based on lanthanide-containing Nb/W mixed-addendum polyoxometalate has been obtained by utilizing the steam-assisted conversion method.

Synthesis, structure, and photocatalytic hydrogen evolution of a trimeric Nb/W addendum cluster

We present the second trimeric Nb/W addendum cluster Cs₁₂[(SiW₉Nb₃O₃₈)₃WO₃(OH)₃]·33H₂O with its photocatalytic hydrogen evolution activity.

Insight into the reactivity of in situ formed {(NbO2)3SiW9}: synthesis, structure, and solution properties of a trimeric polytungstosilicate trapping a {MnNb9} core

The first example of the trimeric polyoxometalate cluster, Cs₁₀Na₃[(SiW₉Nb₃O₃₈)₃MnO₃(H₂O)₃]·18H₂O (1a), has been synthesized using an in situ synthetic strategy and thoroughly characterized.

A rare polyniobotungstate-based framework and its structural transformation in a single-crystal-to-single-crystal process induced by iodide ions

A rare polyniobotungstate-based framework constructed from Lindqvist [Nb₃W₃O₁₉]⁵⁻ polyanions and mixed-valent copper ions has been made, which can undergo a solid–liquid reaction with KI solution to form a copper halide via a single-crystal-to-single-crystal process.

Significant developments in rare-earth-containing polyoxometalate chemistry: synthetic strategies, structural diversities and correlative properties

In this article, the major progress in rare-earth containing polyoxometalates made in the past decade involving synthetic strategies, structural characteristics and some significant properties related to optics, catalysis and magnetism is highlighted and discussed.

Two types of novel tetra-iron substituted sandwich-type arsenotungastates with supporting lanthanide pendants

Two classes of novel tetra-iron substituted sandwich-type arsenotungastates with supporting lanthanide pendants have been synthesized and characterized.