Self-assembly of a unique triangle-like tungstovanadate containing pentagonal {(WO7)W3(SnR)2} cluster

In aqueous solution, a novel triangle-like tungstovanadate estertin derivative K10H10.5[(W4O15(H2O)2){(SnCH2CH2COO)2(V0.75W10.75/V0.25O39)}{{(SnCH2CH2COO)2(μ-OH)}2(SnCH2CH2COO)(VW10O37)}2]·31H2O ((SnR)8-V3W35, R = CH2CH2COO) was assembled by a conventional synthetic method. (SnR)8-V3W35 is composed of one [VW11O39]7- ({VW11}) and two [VW10O37]9- ({VW10}) units connected by eight [Sn(CH2)2COO]2+ groups and a {W4O19} cluster. Interestingly, there exists a pentagonal bipyramid WO7 polyhedral center surrounded by two SnCO5 and three WO6 octahedra, forming a pentagonal {(WO7)W3(SnR)2} cluster in this polyoxometalate (POM), which is also the first example of a pentagonal structure formed by transition metals (TMs) and main group organometals in the POM family. Furthermore, the structure of this organic-inorganic hybrid POM also exhibits the largest number of organotin groups introduced into the POM system. It was characterized with various physico-chemical and spectroscopic methods, including X-ray single crystal and powder diffraction analysis, 119Sn and 51V NMR, IR, thermal gravimetric analysis (TGA), etc. In addition, the catalytic activity of (SnR)8-V3W35 as a mimic of peroxidase was evaluated using o-phenylenediamine (OPD) as a peroxidase substrate. The major factors influencing the oxidation reaction such as pH, the dosage of (SnR)8-V3W35, and concentrations of OPD and H2O2 were mainly studied. (SnR)8-V3W35 exhibits good peroxidase-like catalytic activity. From another perspective, the successful acquisition of (SnR)8-V3W35 further proves the instability and easy reassembly characteristics of TM-sandwich-type tungstovanadates, which also provides a new assembly strategy for synthesizing POM-estertin derivatives.

Heterometallic coordination polymers as heterogeneous electrocatalysts

Heterometallic coordination polymers have been rapidly developed as heterogeneous electrocatalysts. This review highlights the synthesis strategies of these polymers and the relationships between structures and electrocatalytic performances.

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.

Well-tuned white-light-emitting behaviours in multicenter-Ln polyoxometalate derivatives: A photoluminescence property and energy transfer pathway study

White light-emitting diodes (WLEDs) are of scientific significance in terms of their wide applications, and few uminescent materials based on white-light-emitting polyoxometalate (POM) derivatives have been reported till now. Herein, a series of organic chromophores modified POM derivatives [N(CH₃)₄]₃K₂Ln(C₇H₅O₂)(H₂O)₂(α-PW₁₁O₃₉)]·11H₂O (Ln³⁺ = Eu³⁺ (1), Tb³⁺ (2), Tm³⁺ (3), Lu³⁺ (4)) and multicenter-Ln analogues [N(CH₃)₄]₃K₂Eu_xTb_yTm_1-x-y(C₇H₅O₂)(H₂O)₂(α-PW₁₁O₃₉)·11H₂O (5-11) were synthesized successfully and were characterized by various physico-chemical analysis. The investigations indicate the white-light-emitting behavior can be well tuned by adjusting the molar ratio of Eu³⁺/Tb³⁺/Tm³⁺ = 0.06:0.10:0.84 in 9. The energy transfer process from organic benzoic and POM ligands to Eu³⁺, Tb³⁺ and Tm³⁺ emitting centers were detected through time-resolved emission spectroscopy (TRES) and the comparison of excitation of single-, double-, treble-Ln³⁺ mixed, indicating the energy can transfer from the photoexcitation O → M LMCT state of POM components and π → π* transition of organic ligand to sensitize the emissions of Ln³⁺ ions via intramolecular energy transition mechanism. The energy transfer between Eu³⁺ and Tb³⁺, Tm³⁺ and Eu³⁺, Tm³⁺ and Tb³⁺ ions also have been recorded and carefully studied by TRES and variations of Tm³⁺ luminescence lifetime in this context, and the results show a low-effectively process of energy transfer between Tm³⁺/Eu³⁺, Tm³⁺/Tb³⁺ ions and a relatively good energy transfer efficiency between Eu³⁺/Tb³⁺ ions.

Syntheses, structures and properties of three organic–inorganic hybrid polyoxotungstates constructed from {Ni6PW9} building blocks: from isolated clusters to 2-D layers

Three organic–inorganic hybrid POMs were prepared and characterized, exhibiting 0-D to 2-D assemblies made by {Ni₆PW₉} SBUs and organic ligands.

Synthesis, structure and electrochemical characterization of an isopolytungstate (W4O16) held by MnII anchors within a superlacunary crown heteropolyanion {P8W48}

The first example of an isopolyanion (W₄O₁₆) held by redox-active Mn^II anchors within an archetypal superlacunary heteropolyanion {P₈W₄₈}.

Co-crystal structure of a dinuclear (Zn-Y) and a trinuclear (Zn-Y-Zn) complexes derived from a Schiff base ligand

The present investigation describes the synthesis and structural study of a metal-zinc ligand [ZnL.H2O], which was used to generate three dimensional supramolecular complex formulated as [Y{Zn(L)(SCN)}(SCN)2].[Y{Zn(L)(SCN)}2(DMF)2].(NO3). The title compound crystallizes in the triclinic space group P-1 with the following unit cell parameters: a = 14.8987(7) Å, b = 15.6725(8) Å, c = 19.2339(10) Å, a = 94.610(4)°, β = 103.857(4)°, γ = 101.473(4)°, V = 4234.4(4) Å3, Z = 2, R1 = 0.063 and wR2 = 0.96. For this compound, the structure reveals that one heterodinuclear unit [Y{Zn(L)(SCN)}(SCN)2] is co-crystallized with a heterotrinuclear unit [Y{Zn(L)(SCN)}2(DMF)2].(NO3). In the dinuclear moiety, the organic molecule acts as a hexadentate ligand and in the trinuclear unit, it acts as a pentadentate ligand with one of the oxygen methoxy group remaining uncoordinated. In both units the coordination environment of the zinc metal can be described as distorted square pyramidal. In the dinuclear unit the Y(III) is hexacoordinated while it is octacoordinated in the trinuclear unit. The environment of the Y(III) can be described as a distorted octahedral geometry in the dinuclear and as a distorted square antiprism in the trinuclear units respectively.

Synthesis and Characterization of a Heterometallic Extended Architecture Based on a Manganese(II)-Substituted Sandwich-Type Polyoxotungstate

The reaction of [α-P₂W₁₅O₅₆]¹²⁻ with Mn^II and Dy^III in an aqueous basic solution led to the isolation of an all inorganic heterometallic aggregate Na₁₀(OH₂)₄₂[{Dy(H₂O)₆}₂Mn₄P₄W₃₀O₁₁₂(H₂O)₂]·17H₂O (Dy₂Mn₄-P₂W₁₅). Single-crystal X-ray diffraction revealed that Dy₂Mn₄-P₂W₁₅ crystallizes in the triclinic system with space group P1¯, and consists of a tetranuclear manganese(II)-substituted sandwich-type phosphotungstate [Mn₄(H₂O)₂(P₂W₁₅O₅₆)₂]¹⁶⁻ (Mn₄-P₂W₁₅), Na, and Dy^III cations. Compound Dy₂Mn₄-P₂W₁₅ exhibits a 1D ladder-like chain structure based on sandwich-type segments and dysprosium cations as linkers, which are further connected into a three-dimensional open framework by sodium cations. The title compound was structurally and compositionally characterized in solid state by single-crystal XRD, powder X-ray diffraction (PXRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric (TGA), and elemental analyses. Further, the absorption and emission electronic spectra in aqueous solutions of Dy₂Mn₄-P₂W₁₅ and Mn₄-P₂W₁₅ were studied. Also, magnetic properties were studied and compared with the magnetic behavior of [Mn₄(H₂O)₂(P₂W₁₅O₅₆)₂]¹⁶⁻.

A novel 3D POMOF based on Wells–Dawson arsenomolybdates with excellent photocatalytic and lithium-ion battery performance

A novel 3D POMOF based on Wells–Dawson arsenomolybdates exhibits fluorescence property and efficient and stable photocatalytic activity for MB and RhB under UV irradiation and has also been evaluated as the anode material for LIBs.

Lanthanoid Template Isolation of the α-1,5 Isomer of Dicobalt(II)-Substituted Keggin Type Phosphotungstates: Syntheses, Characterization, and Magnetic Properties

A new series of heterometallic 3d-4f sandwich type phosphotungstates, [Ln{PCo2W10O38(H2O)2}2](11-) (Ln = Sm(III), Eu(III), Gd(III), Tb(III), Dy(III), Ho(III), Er(III), Tm(III), Yb(III), and Lu(III), denoted 1a-10a, respectively), have been synthesized by a one-pot reaction procedure on reacting the dilacunary K14[P2W19O69(H2O)]·24H2O precursor with Ln(NO3)3·nH2O and Co(NO3)2·6H2O in an aqueous potassium chloride solution. All the compounds were isolated as potassium salts and further characterized with different analytical techniques such as single-crystal X-ray diffraction, Fourier transform infrared spectroscopy, high-resolution electrospray ionization mass spectrometry, elemental analysis by inductively coupled plasma atomic emission spectroscopy, magnetic measurement, and thermogravimetric analysis. Single-crystal X-ray diffraction analysis of the compounds reveals that all these compounds are isostructural and crystallized in the orthorhombic crystal system in space group Iba2. The polyanions contain the α-1,5 isomer of dicobalt-substituted α-Keggin phosphotungstate, which sandwiched lanthanoid cation and formed novel heterometallic dimer species. The temperature-dependent magnetic susceptibilities of 1a, 2a, 4a, and 7a-10a indicate the dominant contribution of the ferromagnetic interaction between Co(II) and Co(II) within the cluster, while the antiferromagnetic interaction between Co(II) and Ln(III) dominates for 3a, 5a, and 6a. The isothermal magnetizations of 1a-10a show a gradual increase in magnetization at low fields and do not reach saturation even at 50 kOe.

Two New Armtype Polyoxometalates Grafted on Titanium Dioxide Films: Towards Enhanced Photoelectrochemical Performance

Two new carboxyethyltin-functionalized polyoxometalates (POMs) were successfully obtained and confirmed with physicochemical and spectroscopic methods including X-ray crystallography. The lowest unoccupied molecular orbitals of both compounds are higher in energy than that of TiO2 , and the optical band gaps of these compounds are smaller than that of TiO2 . Grafting them onto a TiO2 film created two kinds of novel photoanode materials that showed significantly enhanced photovoltaic and photocurrent responses, as well as improved photoelectrooxidation activities for methanol relative to that shown by a single TiO2 film. Further, P2 W15 -Co-SnR produced the largest photocurrent by exploring the photoelectric activities of a series of carboxyethyltin POM derivatives. This work provides new insight into the photoelectrochemical functionalization of POM-based organic-inorganic hybrids.

Research progress on polyoxometalate-based transition-metal–rare-earth heterometallic derived materials: synthetic strategies, structural overview and functional applications

This review summarizes the structural types of reported polyoxometalate-based transition-metal–rare-earth heterometallic derived materials (PTRHDMs) together with synthetic strategies, structural motifs and relevant functional applications.

An open chain carboxyethyltin functionalized sandwich-type tungstophosphate based on a trivacant Dawson subunit: synthesis, characterization and properties

A Dawson sandwich-type polyoxometalate {C(NH2)3}12H4[αββα-{(Sn(C3H4O2))2Mn2(P2W15O56)2}]·22H2O (abbreviated as SnR-Mn-P2W15), functionalized by open chain carboxyethyltin groups, was first prepared in aqueous solution under conventional reaction conditions, and then structurally characterized by physicochemical and spectroscopic methods. Single crystal X-ray diffraction analysis revealed that two Mn(2+) cations and two [Sn(CH2CH2COO)](2+) groups are located in the internal and external positions in the so-called equatorial region of SnR-Mn-P2W15, respectively. Intriguingly, two exposed carboxyl groups act as stretching-arm brackets, which provide a favorable structure for potential further functionalization. The electrocatalytic activity of SnR-Mn-P2W15 towards the reduction of hydrogen peroxide and nitrite was studied. Additionally, its acid catalysis and oxidation catalysis activities in organic synthesis were investigated.

An unprecedented 3D POM–MOF based on (7,8)-connected twin Wells–Dawson clusters: synthesis, structure, electrocatalytic and photocatalytic properties

The first (7,8)-connected POM–MOF has been obtained, representing the highest connected POMs to any mixed-connected POM–MOF and a unique structure that contains organic–inorganic and all-inorganic networks.

Mesoxalate as Cu(ii)–Ln(iii) linker in the construction of MOFs in DMSO/water medium

The combination of [Cu₃(Hmesox)₃]³⁻ with La(iii), Ce(iii), Pr(iii), Nd(iii) and Eu(iii) in DMSO/H₂O yields 3d–4f heterometallic metal–organic frameworks, with the dimensionality of the network being controlled by the coordination number of the Ln(iii) ion.

Two Keggin sandwich-type tungstophosphates modified by open-chain carboxyethyltin groups and transition metals

Two new crystalline Keggin sandwich-type POMs containing open-chain carboxyethyltin groups showed good fluorescence quenching effects and oxidation catalytic activities.