Polyoxometalates represent a diverse range of molecular clusters with an almost unmatched range of physical properties and the ability to form structures that can bridge several length scales. The new building block principles that have been discovered are beginning to allow the design of complex clusters with desired properties and structures and several structural types and novel physical properties are examined. In this critical review the synthetic and design approaches to the many polyoxometalate cluster types are presented encompassing all the sub-types of polyoxometalates including, isopolyoxometalates, heteropolyoxometalates, and reduced molybdenum blue systems. As well as the fundamental structure and bonding aspects, the final section is devoted to discussing these clusters in the context of contemporary and emerging interdisciplinary interests from areas as diverse as anti-viral agents, biological ion transport models, and materials science.

Polyoxometalate clusters, nanostructures and materials: From self assembly to designer materials and devices

Nine new coordination polymers, namely, [Mn2(L)(H2O)4]·H2O (1), [Cd(L)0.5(H2O)] (2), [Zn5(L)2(μ3-O)2(H2O)4]·2H2O (3), [Zn4(L)2(μ3-O)2][Zn(H2O)5]·2H2O (4), [Zn2(L)(biim-4)0.5(H2O)3]·H2O (5), [Cd2(L)(bpy)(H2O)]·2H2O·0.5(CH3CH2OH) (6), [Cu2(H2L)2(bpy)2] (7), [Cu2(L)(bpy)(H2O)] (8), and [Cu2(L)(bpy)1.5(H2O)2.5] (9), where H4L = 1,2,3,4-benzenetetracarboxylic acid, biim-4 = 1,1′-(1,4-butanediyl)bis(imidazole), and bpy = 4,4′-bipyridine, have been synthesized under hydrothermal conditions. Compound 1 displays a rare trinodal (3,4,7)-connected (42·6)(45·6)(47·68·86) topology. 2 possesses an α-Po net. 3 is a novel 3D framework based on pentanuclear ZnII clusters. By adjustment of the pH values of the reaction mixture of 3 with a Na2CO3 solution, a structurally different compound, 4, was obtained, which exhibits a 3D porous framework with the [Zn(H2O)6]2+ cations located in the channels. 5 is an unusual example of a trinodal (3,5)-connected network with a Schlafli symbol of (42·6)(62·8)(42·62·85·10), whereas 6, co...

Series of 2D and 3D Coordination Polymers Based on 1,2,3,4-Benzenetetracarboxylate and N-Donor Ligands: Synthesis, Topological Structures, and Photoluminescent Properties

Recent advances in the design and construction of helical coordination polymers

Rational self-assembly of a long V-shaped 3,3',4,4'-benzophenonetetracarboxylate (bptc) ligand and metal salts in the presence of linear bidentate ligand yield a series of novel pillared helical-layer complexes, namely, [Cu2(bptc)(bpy)2] (1), [M3(Hbptc)2(bpy)3(H2O)4].2 H2O (M = Fe(2) and Ni(3)), [Co2(bptc)(bpy)(H2O)].0.5 bpy (4), [Cd2(bptc)(bpy)(H2O)2].H2O (5), [Mn2(bptc)(bpy)1.5(H2O)3] (6) and [M2(bptc)(bpy)0.5(H2O)5].0.5 bpy (M = Mn(7), Mg(8) and Co(9), bpy=4,4'-bipyridine). Their structures were determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, and thermogravimetric (TG) analyses. The structure of 1 consists of two types of chiral layers, one left-handed and the other right-handed, which are connected by bpy pillars to generate a novel 3D open framework featuring four distinct helical chains. Compounds 2 and 3 are isostructural and feature 3D structures formed from the interconnection of arm-shaped helical layers with bpy pillars. Compound 4 is a pillared helical double-layer complex containing four different types of helices, among which the nine-fold interwoven helices constructed from triple-stranded helical motifs are unprecedented. Compound 5 exhibits a novel 3D covalent framework which features nanosized tubular channels. These channels are built from helical layers pillared by bptc ligands. The structure of 6 is constructed from {Mn(bptc)(H2O)}n2n- layers, which consist of left- and right-handed helical chains, pillared by [Mn2(bpy)3(H2O)4]4+ complexes into a 3D framework. To the best of our knowledge, compounds 1-6 are the first examples of pillared helical-layer coordination polymers. Compounds 7-9 are isostructural and exhibit interesting 2D helical double-layer structures, which are constructed from {M(bptc)(H2O)2}n2n- ribbons cross-linked by [M2(bpy)(H2O)6]4+ complexes. Furthermore, the 3D supramolecular structures of 7-9 are similar to the 3D structure of 6, and the 2D structure of 7 can be transformed into the 3D structure of 6 at higher reaction temperature. By inspection of the structures of 1-9, it is believed that the V-shaped bptc ligand and V-shaped phthalic group of the bptc ligand are important for the formation of the helical structures. The magnetic behavior of compounds 1, 2, 4, 6, and 9 was studied and indicated the existence of antiferromagnetic interactions. Moreover, compound 5 shows intense photoluminescence at room temperature.

A bridge between pillared-layer and helical structures: a series of three-dimensional pillared coordination polymers with multiform helical chains.

Enantiomerically pure polytungstates: chirality transfer through zirconium coordination centers to nanosized inorganic clusters.

A novel left-handed double helicate constructed from L-tartrate bridged molybdenum(VI) and gadolinium(III) atoms

Hydrothermal synthesis of two new zinc coordination polymers with mixed ligands

Two new members of Mo(V) phosphates were synthesized by hydrothermal methods. (enH2)(enH)[NaMo12O24(OH)6(HPO4)2(H2PO4)6]·(en)4·20H2O(1)(en=H2 NCH2CH2NH2)[HAD-H2]2[HAD-H]2[Zn3Mo12O24(OH)6(PO4)2(HPO4)6]·6H2O (2) (HAD=H2N(CH2)6NH2). Compound 1 crystallized in the space group P2(1)/n, a=15.93120(10) A, b=15.8946(2) A, c=17.0665(2) A, V=4316.02(8), β=92.9060(10)°, Z=2. Compound 2 crystallized in the space group P(−1) with a=12.3726(3) A, b=14.1948(3) A, c=14.2310(4) A, α=72.7100(10), β=65.0230(10), γ=69.5600(10)°, Z=2089.70(9) A3, and Z=1. The structure of 1 consists of sandwich-shaped cluster anion [Na{MoV6O12(OH)3(HPO4)(H2PO4)3}2]3− ({Na(MoV6)2}) held together via intermolecular hydrogen-bonding contacts. For the compound 2, the sandwich-shaped clusters Zn[Mo6O12(OH)3(PO4)(HPO4)3]2 ({Zn(MoV6)2} are linked by tetrahedrally-coordinated zinc into layers. Organic cations ([H3N(CH2)6NH3]2+ and [H3N(CH2)6NH2]+) are filled in the spaces between lamellas. The layers are held together by a hydrogen-bonded network, which involves the terminal phosphate P-OH groups, as well as organic cations and several waters of solvation.

Hydrothermal Synthesis and Structure of Two New Mo(V)-Oxide Phosphates

An interesting network of an asymmetric binuclear molybdenum complex formed via OH⋯O and CH⋯OCO hydrogen bonds and stacking interactions

The title compound, [Na2Zn(C10H4O8)2(H2O)8]·2H2O, consists of six-coordinated Zn2+ and Na+ cations, aqua ligands, crystal water mol­ecules and di­hydrogen 1,2,4,5-benzene­tetra­carboxyl­ate(2−) (H2btc) anions. The six-coordinated zinc centers, which are situated at the inversion center, are linked into one-dimensional chains via six coordinated sodium ions in pairs and extended further into a three-dimensional framework via hydrogen bonding.

Ding-Ming Wu

Papers

A novel left-handed double helicate constructed from L-tartrate bridged molybdenum(VI) and gadolinium(III) atoms

Hydrothermal synthesis of two new zinc coordination polymers with mixed ligands

Hydrothermal Synthesis and Structure of Two New Mo(V)-Oxide Phosphates

An interesting network of an asymmetric binuclear molybdenum complex formed via OH⋯O and CH⋯OCO hydrogen bonds and stacking interactions

Octaaquabis[dihydrogen 1,2,4,5-benzenetetracarboxylate(2–)]disodium(I)zinc(II) dihydrate

Ding-Ming Wu

Papers

A novel left-handed double helicate constructed from L-tartrate bridged molybdenum(VI) and gadolinium(III) atoms

Hydrothermal synthesis of two new zinc coordination polymers with mixed ligands

Hydrothermal Synthesis and Structure of Two New Mo(V)-Oxide Phosphates

An interesting network of an asymmetric binuclear molybdenum complex formed via OH⋯O and CH⋯OCO hydrogen bonds and stacking interactions

Octa­aqua­bis­[di­hydrogen 1,2,4,5-benzene­tetra­carboxyl­ate(2–)]­disodium(I)­zinc(II) dihydrate

Octaaquabis[dihydrogen 1,2,4,5-benzenetetracarboxylate(2–)]disodium(I)zinc(II) dihydrate