A polyoxometalate-based metal-organic polyhedron constructed from a {V5O9Cl} building unit with rhombicuboctahedral geometry.

The design and construction of metal-organic polyhedra has received much attention by chemists due to the intriguing diversity of architectures and topologies that can be achieved. There are several crucial factors which should be considered for the construction of metal-organic polyhedra, such as the starting materials, reaction time and temperature, solvent and suitable organic ligands. Recently, polyoxometalates (POMs), serving as secondary building units to construct POM-based metal-organic polyhedra, have been the subject of much interest. The title compound, dodecakis(dimethylammonium) octakis(µ-benzene-1,3,5-tricarboxylato)hexa-µ-chlorido-tetracosa-µ-oxido-triacontaoxidotriacontavanadium, (NH2Me2)12[(V5O9Cl)6(C9H3O6)8], was synthesized successfully by self-assembly of VOCl3 and benzene-1,3,5-tricarboxylic acid under solvothermal conditions. The title polyhedron has an rdo topology when the {V5O9Cl} building unit and the benzene-1,3,5-tricarboxylate (BTC3-) ligand were simplified into 4-connected and 3-connected vertices. Interestingly, when the {V5O9Cl} building unit and the BTC3- ligand are considered as quadrangular and triangular faces, the structure displays rhombicuboctahedral geometry with an outer diameter of 21.88 Å. The packing of the polyhedra produces a circular channel with a diameter of 8.2 Å. The title compound was characterized by single-crystal X-ray diffraction, elemental analysis, IR spectroscopy, thermogravimetric analysis and powder X-ray diffraction.

Functionalized polyoxometalate-based metal-organic cuboctahedra for selective adsorption toward cationic dyes in aqueous solution.

Two functionalized polyoxovanadate-based metal-organic polyhedra with heterocube formations are synthesized under solvothermal conditions. The structures of VMOP-18 and VMOP-19 display similar cuboctahedral geometries when the polyoxovanadate {V6O6(OCH3)9X(COO)3}n- (X = VO4, n = 1; SO4, n = 2) building units and organic ligands are considered as triangular faces of the polyhedra. Each cuboctahedron was surrounded by eight neighbouring cuboctahedra via strong C-Hπ interactions, leading to a 3D open supramolecular structure. Furthermore, the absorption ability toward the ionic dyes of VMOP-18 was investigated. Only cationic dyes can be absorbed into the cavity of VMOP-18, which indicates that the cationic dye absorption process is an ion-exchange process.

Synthesis, structures, and magnetic properties of metal-organic polyhedra based on unprecedented {V7} isopolyoxometalate clusters.

Two isostructural vanadium-based metal-organic polyhedra (denoted as VMOP-16 and VMOP-17) were synthesized by a solvothermal method, which are built from unprecedented {V7} isopolyoxometalate clusters and dicarboxylate ligands. To our knowledge, the {V7} second building unit is reported for the first time and features the highest nuclearity of vanadium-oxygen clusters compared with reported vanadium-based MOPs.

Anderson-like alkoxo-polyoxovanadate clusters serving as unprecedented second building units to construct metal-organic polyhedra.

Unprecedented Anderson-like alkoxo-polyoxovanadate [V6O6(OCH3)9(µ6-SO4)(COO)3](2-) polyanions can serve as 3-connected second building units (SBUs) that assemble with dicarboxylate or tricarboxylate ligands to form a new family of metal organic tetrahedrons of V4E6 and V4F4 type (V = vertex, E = edge, and F = face). To our knowledge, this alkoxo-polyoxovanadate-based SBU is the first ever reported.