One Octasubstituted Trisalkoxotetradecavanadate Cluster

New types of open-framework vanadium borophosphates with photocatalytic properties

The exploration of new open-framework polyoxometalates is very significant in structural chemistry and materials science. Herein, three new organic hybrid three-dimensional vanadium borophosphates (H3O)7(H2aeae)3{[Cd(H2O)3]2[H3O⊃(V2BP2O12)6]}·15H2O (1, aeae = 2-(2-aminoethylamino)ethanol) and (H3O)5(H2aeae)3{[TM(H2O)2.5(H2aeae)0.5]2[H3O⊃ (V2BP2O12)6]}·9H2O [TM = Mn(2), Co(3)] were hydrothermally prepared and structurally characterized. The three vanadium borophosphates contain similar 12-member ring crown-shaped clusters [(V2BP2O12)6]18- based on the linkage of six [V2O8] dimers and six [BP2O10] units. The [(V2BP2O12)6]18- cluster is further bridged by the unsaturated [Cd(H2O)3]2+ or [TM(H2O)2.5(H2aeae)0.5]3+ complexes to build new types of open-framework vanadium borophosphates with pores and cavities retained by the protonated H2aeae2+, H3O+ and free H2O. Surprisingly, the monodentate H2aeae2+ ligand coordinating with a metal center was observed in 2 and 3 for the first time as the aeae molecule acted as the trichelating ligand. Their optical absorption edges were determined to be in the range of 2.61-2.68 eV using solid-state UV-vis spectroscopy. 1-3 exhibited excellent photocatalytic activity towards methylene blue (MB) degradation under visible light irradiation, which presented the first example of organic hybrid open-framework vanadium borophosphates as the photo-catalysts for MB degradation.

A series of organic hybrid polyoxovanadate clusters incorporating tris(hydroxymethyl)methane derivatives

A series of new organic hybrid polyoxovanadate clusters [V₄O₄(μ-OH)₂(acac)₂(Htri)₂] (1, H₃tri = tris(hydroxymethyl) aminomethane, acac = acetylacetone), [V₄O₄(acac)₂(Htri)₂(L)₂] {HL = methanol (2), ethanol (3a and 3b), ethylene glycol (4) and benzyl alcohol (5)}, {V₄O₄(H₂O)₂(tri-acetamide)₂(CH₃COO)₂} (6, H₃tri-acetamide = N-(2-hydroxy-1,1-bis-hydroxymethyl-ethyl)-acetamide), [V₆O₈(μ-OH)₂(Htri)₃]·6H₂O (7) and [V₁₄O₁₈(tri)₂(Htri)₆(HCOO)(CH₃COO)]·2H₂O (8) were prepared by hydro(solvo)thermal methods and characterized structurally. 1 contains [VO(OH)(acac)] and [VO₂(Htri)] units, which are further interconnected via common edges to build a tetravanadyl cluster [V₄O₄(OH)₂(acac)₂(Htri)₂] with the double-deficient cube [V₄O₆]. The tetravanadyl cluster frameworks of 2-5 can be derived from the tetravanadyl cluster of 1 by replacing two -OH groups with two deprotonated organic alcohol ligands, namely, CH₃O^- (2), CH₃CH₂O^- (3a and 3b), HO(CH₂)₂O^- (4) and C₆H₅CH₂O^- (5). Interestingly, both 3a and 3b have the same chemical structure, but they exhibit different conformational polymorphisms [denoted as α-type (3a) and β-type (3b)]. Such conformational polymorphisms within the polyoxovanadate clusters incorporating tris(hydroxymethyl)methane derivatives emerged for the first time. 6 displays another tetravanadyl cluster {V₄O₄(H₂O)₂(tri-acetamide)₂(CH₃COO)₂} with a [V₄O₁₆] fragment, where the tri-acetamide unit comes from the amidation reaction of H₃tri and acetic acid and caps the tetrahedral void of the tetravanadyl cluster. The polyoxovanadate cluster of 7 can originate from the Lindqvist-type hexavanadyl cluster [V₆O₁₉] by replacing nine μ-oxides with nine alkoxides of three tri-acetamide^3- ligands. 8 exhibits a fully reduced tetradecavanadyl cluster based on the linkage of two heptavanadyl clusters via two O bridges. The magnetic properties of 1-8 show typical antiferromagnetic interactions.

Organo-functionalized polyoxovanadates: crystal architecture and property aspects

Polyoxovanadates (POVs), as one of the most prominent members of polyoxometalates (POMs), have been subject to extensive studies by virtue of their aesthetically intriguing structures and potential applications in catalysis, magnetism, and optics, among others. In recent years, organo-functionalized POVs have received considerable attention due to the combination of the advantages of POVs with the importance of organic species. In this review, the key developments of polyoxovanadates and, particularly, the achievements that are related to polyoxovanadates modified with organic ligands and transition metal-organic ligand are summarized. Herein, we systematically introduce the structural features of organo-functionalized POVs and their main applications involved in the magnetism and catalysis aspects. Finally, the current challenges and future prospects in the design, synthesis, and property investigation of polyoxovanadates are also discussed.