Lanthanide complexes of macrocyclic polyoxovanadates by VO4 units: synthesis, characterization, and structure elucidation by X-ray crystallography and EXAFS spectroscopy

(3+1)-Dimensional Modulated Structure and Tb3+-Doped Luminescence for Vanadate Na3La(VO4)2

A modulated structure with symmetrical characteristic higher than three-dimensional is a fascinating crystallographic type, and it is randomly encountered by researchers. Herein, we prepared 0.1 mm level single crystals of Na₃La(VO₄)₂ and determined its structure to be a (3 + 1)-dimensional modulated structure using the X-ray diffraction analysis method for single crystals. Its super space group was determined to be Pca2₁(0β0)000. On the other hand, we introduced Tb³⁺ into the Na₃La(VO₄)₂ host lattice to fabricate phosphors Na₃La_1-x(VO₄)₂:xTb³⁺ and studied their photoluminescence properties. Interestingly, for the strong absorption of the Na₃La(VO₄)₂ host lattice in the range of 200-400 nm, the traditional 330-385 nm light is unable to efficiently excite Tb³⁺ ions in the Na₃La(VO₄)₂ host to generate luminescence of Tb³⁺. Instead, Na₃La_1-x(VO₄)₂:xTb³⁺ is suitable to be excited by 487 nm to generate emitting light at 543, 584, and 622 nm, due to Tb³⁺ characteristic 4f → 4f transitions of ⁵D₄ → ⁷F_J (J = 5, 4, 3). Hence, the Tb³⁺-doped Na₃La(VO₄)₂ phosphors have potential applications for white-light-emitting diodes.

Molecular Vanadium Oxides for Energy Conversion and Energy Storage: Current Trends and Emerging Opportunities

Molecular vanadium oxides, or polyoxovanadates (POVs), have recently emerged as a new class of molecular energy conversion/storage materials, which combine diverse, chemically tunable redox behavior and reversible multielectron storage capabilities. This Review explores current challenges, major breakthroughs, and future opportunities in the use of POVs for energy conversion and storage. The reactivity, advantages, and limitations of POVs are explored, with a focus on their use in lithium and post-lithium-ion batteries, redox-flow batteries, and light-driven energy conversion. Finally, emerging themes and new research directions are critically assessed to provide inspiration for how this promising materials class can advance research in sustainable energy technologies.

Beyond Charge Balance: Counter-Cations in Polyoxometalate Chemistry

Polyoxometalates (POMs) are molecular metal-oxide anions applied in energy conversion and storage, manipulation of biomolecules, catalysis, as well as materials design and assembly. Although often overlooked, the interplay of intrinsically anionic POMs with organic and inorganic cations is crucial to control POM self-assembly, stabilization, solubility, and function. Beyond simple alkali metals and ammonium, chemically diverse cations including dendrimers, polyvalent metals, metal complexes, amphiphiles, and alkaloids allow tailoring properties for known applications, and those yet to be discovered. This review provides an overview of fundamental POM-cation interactions in solution, the resulting solid-state compounds, and behavior and properties that emerge from these POM-cation interactions. We will explore how application-inspired research has exploited cation-controlled design to discover new POM materials, which in turn has led to the quest for fundamental understanding of POM-cation interactions.

A simple one-step synthetic route to access a range of metal-doped polyoxovanadate clusters

A simple one-step synthetic route to access a range of metal-doped polyoxovanadate clusters.

A highly-flexible cyclic-decavanadate ligand for interconversion of dinuclear- and trinuclear-cobalt(ii) and manganese(ii) cores

The conformation of a cyclic-decavanadate ligand was reversibly transformed in response to the nuclearity of the central metal core.

Lanthanide contraction and chelating effect on a new family of lanthanide complexes with tetrakis(O-isopropyl)methyle-nediphosphonate: synthesis, structures and terahertz time-domain spectroscopy

Sixteen lanthanide–diphosphate complexes have been synthesized by the reaction of lanthanide chlorides and tetrakis(O-isopropyl)methylenediphosphonate ligand in the solvent of acetonitrile (with ethanol or DMF) at room temperature.

Synthesis and characterization of fluoride-incorporated polyoxovanadates

The speciation studies of oxovanadates are essential to clarify their biological activities. We surveyed the distribution of oxovanadate species in the presence of halide anions with various acid concentrations in an aqueous mixed-solvent system. The presence of chloride, bromide, and iodide anions has no effects on the appearance of polyoxovanadate species observed in (51)V NMR. Those are the precedent formation of metavanadate species and decavanadates. The presence of fluoride anion during the addition of acids exhibits strong intervention in the polyoxovanadate equilibria and we found the subsequent formation of two polyoxovanadate species by (51)V NMR observation. From the estimated experimental condition, we isolated fluoride-incorporated polyoxovanadates {Et4N}4[V7O19F] and {Et4N}4[HV11O29F2], successfully. Polyanion [V7O19F](4-) is the fluoride-incorporated all V(V) state polyoxovanadate which has two different coordination environments of tetrahedral and square pyramidal vanadium units within the one anionic structural integrity. The structural gap between tetrahedral-unit-based metavanadate and octahedral-unit-based decavanadate structures may be linked by this hybrid complex.

Polyoxometalate-directed assembly of various multinuclear metal–organic complexes with 4-amino-1,2,4-triazole and selective photocatalysis for organic dye degradation

Five POM-based metal–organic complexes ranging from 0D trinuclear cluster, 1D chain, 2D network, to 3D framework have been successfully prepared in the presence/absence of citric or boric acid.

A new class of homogeneous visible-light photocatalysts: molecular cerium vanadium oxide clusters

The first systematic access to molecular cerium vanadium oxides is presented. A family of structurally related, di-cerium-functionalized vanadium oxide clusters and their use as visible-light-driven photooxidation catalysts is reported. Comparative analyses show that photocatalytic activity is controlled by the cluster architecture. Increased photoreactivity of the cerium vanadium oxides in the visible range compared with nonfunctionalized vanadates is observed. Based on the recent discovery of the first molecular cerium vanadate cluster, (nBu4 N)2 [(Ce(dmso)3 )2 V12 O33 Cl]⋅2 DMSO (1), two new di-cerium-containing vanadium oxide clusters [(Ce(dmso)4 )2 V11 O30 Cl]⋅DMSO (2) and [(Ce(nmp)4 )2 V12 O32 Cl]⋅NMP⋅Me2 CO (3; NMP=N-methyl-2-pyrrolidone) were obtained by using a novel fragmentation and reassembly route. Pentagonal building units {(V)M5 } (M=V, Ce) reminiscent of "Müller-type" pentagons are observed in 2 and 3. Compounds 1-3 feature high visible-light photooxidative activity, and quantum efficiencies >10 % for indigo photooxidation are observed. Photocatalytic performance increases in the order 1<3<2. Mechanistic studies show that the irradiation wavelength and the presence of oxygen strongly affect photoreactivity. Initial findings suggest that the photooxidation mechanism proceeds by intermediate formation of hydroxyl radicals. The findings open new avenues for the bottom-up design of sunlight-driven photocatalysts.

A new ring-like arrangement of vanadyl(IV) groups bridged by monodentate alkoxides: cyclo-decakis(μ-cyclohexylmethanolato)pentakis[oxidovanadium(IV)]

The pentanuclear title compound, [V(5)(C(7)H(13)O)(10)O(5)], has a metal-oxygen core that consists of five vanadyl(IV) centres bridged by the O atoms of cyclohexylmethanolate ligands. This particular ring topology is new to oxovanadium(IV) chemistry and resembles the structure proposed for [V(5)O(15)](5-) on the basis of (51)V NMR studies in aqueous solution. The bulky cyclohexylmethanolate ligands adopt chair-like conformations and project outwards from the central cyclic core. The title compound crystallizes in a centrosymmetric triclinic unit cell, which contains four independent but chemically identical molecules in the asymmetric unit. The crystal structure is devoid of any significant intermolecular interactions.