Uniform NiS2 nanocubes are successfully synthesized with a microwave-assisted method. Interestingly, NiS2 nanocubes, nanospheres and nanoparticles are obtained by controlling microwave reaction time. NiS2 nanomaterials are primarily applied to supercapacitors and cocatalytic enhancing photocatalytic H2 production. Different morphologies of NiS2 nanostructures show different electrochemical and cocatalytic enhancing H2 production activities. Benefited novel nanostructures, NiS2 nanocube electrodes show a large specific capacitance (695 F g−1 at 1.25 A g−1) and excellent cycling performance (the retention 93.4% of initial specific capacitance after 3000 cycles). More importantly, NiS2 nanospheres show highly cocatalytic enhancing photocatalytic for H2 evolution, in which the photocatalytic H2 production is up to 3400 μmol during 12 hours under irradiation of visible light (λ>420 nm) with an average H2 production rate of 283 μmol h−1.

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Microwave-assisted synthesis of NiS2 nanostructures for supercapacitors and cocatalytic enhancing photocatalytic H2 production.

High-nuclearity cobalt coordination clusters: Synthetic, topological and magnetic aspects

Ortho-vanillin became very popular in coordination chemistry because of its Schiff bases, which generate a rich variety of complexes, ranging from oligonuclear species to coordination polymers. Some of these organic molecules are particularly useful in metallosupramolecular chemistry for assembling homo- and heterometallic helicates. The Schiff bases obtained using aminoalcohols open the door to the synthesis of homo- and heterometallic clusters with various nuclearities and surprising topologies of the metal centers. Several relevant structural types are reviewed. The heterobinuclear 3d-3d' and 3d-4f complexes are valuable building-blocks for the synthesis of heterotrimetallic systems. Beyond the richness of this chemistry, the complexes obtained from o-vanillin-based Schiff ligands show interesting properties: magnetism, luminescence, chirality, catalysis, cytotoxicity, and ferroelectricity. This paper reviews recent data that illustrate a very fertile and dynamic research field in coordination chemistry and materials science.

The exceptionally rich coordination chemistry generated by Schiff-base ligands derived from o-vanillin.

Acyclic and cyclic compartmental ligands: Recent results and perspectives

A three-dimensional (3D) coordination polymer, [Co3(L)2(BTEC)(H2O)2]·2H2O [1, HL = 3,5-di(imidazol-1-yl)benzoic acid, H4BTEC = 1,2,4,5-benzenetetracarboxylic acid], with tfz-d topology has been hydrothermally synthesized. The framework of 1 has high thermal stability and exhibits single-crystal-to-single-crystal (SCSC) transformations upon removing and rebinding the noncoordinated and coordinated water molecules. X-ray crystallographic analyses revealed that the coordination geometry of Co(II) changes from octahedral to square pyramid upon dehydration, accompanying the appearance of one-dimensional (1D) open channels with dimensions of 2.0 × 2.8 A. The dehydrated form [Co3(L)2(BTEC)] (2) exhibits highly selective adsorption of water molecules over N2, CH3OH, and CH3CH2OH, which could be used as sensors for water molecules. Furthermore, the magnetic properties of 1 and 2 were investigated, showing the existence of ferromagnetic interaction between the Co(II) atoms within the trinuclear subunit.

Reversible single-crystal-to-single-crystal transformation and highly selective adsorption property of three-dimensional cobalt(II) frameworks.

The reaction of Co(ClO4)2·6H2O with a disodium 2-[(2-hydroxy-3-methoxy-enzylidene)-amino]-ethanesulfonic acid (Na2L) in a mixture solution (methanol : acetonitrile = 1 : 1 (v/v)) or an acetonitrile solution under microwave and controlled pressure/temperature, or solvothermal conditions leads to the formation of two completely different CoII complexes: heptanuclear cluster [Co7(immp)6(CH3O)6]·2ClO4 (1) (immp is 2-iminomethyl-6-methoxy-phenolic anion) and tetra-heteronuclear cubane cluster [NaCo3(L)3(CH3CN)3(OH)]2·CH3CN (2). The microwave-assisted reactions can improve the reaction rate and yield compared to simple solvothermal synthesis. The magnetic investigation shows that complexes 1 and 2 exhibit a ferromagnetic coupling between the CoII ions. AC susceptibilities of the two complexes reveal no frequency-dependent out-of-phase signals and the corresponding magnetic properties were discussed.

Microwave-assisted synthesis, crystal structure and properties of a disc-like heptanuclear Co(II) cluster and a heterometallic cubanic Co(II) cluster

Three new polynuclear complexes, [Co7(bm)12]·(ClO4)2·13H2O (1), [Co4(bm)4Cl4(C3H7OH)4] (2), and [Co4(bm)4(μ-HCO2)2(μ2-HCO2)2(C3H7OH)2] (3) (Hbm = (1H-Benzimidazol)-methanol), have been synthesized and characterized by elemental analysis, IR, powder X-ray diffraction and X-ray single-crystal diffraction. Compound 1 features a centrosymmetric wheel-like heptanuclear Co(II) cluster. Compound 2 having a I41/a space group exhibits a tetranuclear Co(II) cluster with a cubane topology in which the central Co(II) ion and oxygen atoms from bm occupy the alternate vertices of the cube. However, compound 3 has a tetranuclear Co(II) cluster with a C2/c space group different from that of compound 2. These results show that the geometries and sizes of the corresponding anions as well as their coordinating and hydrogen-bonding properties are essential in determining the final structures of the assemblies. Magnetic properties of 1–3 in the 2–300 K have also been discussed. The {Co7} (1) and {Co4} (2) cores display dominant ferromagnetic interactions while the {Co4} (3) core displays dominant anti-ferromagnetic interactions.

Anion induced diversification from heptanuclear to tetranuclear clusters: syntheses, structures and magnetic properties.

A family of cubane cobalt and nickel clusters: Syntheses, structures and magnetic properties

In the title compound, [Co(C19H12N5)2], each CoII atom occupies a position of high site symmetry, 222, and is coordinated by the six N atoms [Co—N = 2.085 (4)–2.157 (3) A] from two tridentate 2-[6-(1H-benzimidazol-2-yl)-2-pyrid­yl]­benz­imi­dazol­ide ligands in a distorted octa­hedral geometry.

Hong Liang

Papers

Microwave-assisted synthesis, crystal structure and properties of a disc-like heptanuclear Co(II) cluster and a heterometallic cubanic Co(II) cluster

Anion induced diversification from heptanuclear to tetranuclear clusters: syntheses, structures and magnetic properties.

A family of cubane cobalt and nickel clusters: Syntheses, structures and magnetic properties

Bis{2-[6-(1H-benzimidazol-2-yl-κN3)-2-pyridyl-κN]benzimidazolido-κN}cobalt(II)