Heptanuclear Mixed-Valence Co4IIICo3II Molecular Wheel─A Molecular Analogue of Layered Double Hydroxides with Single-Molecule Magnet Behavior and Electrocatalytic Activity for Hydrogen Evolution Reactions

We present a bifunctional heptanuclear cobalt(II)/cobalt(III) molecular complex formulated as [Co7(μ3-OH)4(H2L1)2(HL2)2](NO3)6·6H2O (1) (where H5L1 is 2,2'-(((1E,1'E)-((2-hydroxy-5-methyl-1,3-phenylene)bis(methanylylidene))bis(azanylylidene))bis(propane-1,3-diol)) and H2L2 is 2-amino-1,3-propanediol). Compound 1 has been characterized by single-crystal X-ray diffraction analysis along with other spectral and magnetic measurements. Structural analysis indicates that 1 contains a mixed-valence Co7 cluster where a central Co(II) ion is connected to six different Co centers (four CoIII and two CoII ions) by four μ3-OH groups, giving rise to a planar heptanuclear cluster that resembles a molecular fragment of a layered double hydroxide (LDH). Two triply deprotonated (H2L1)3- ligands form the outer side of the cluster while two singly deprotonated (HL2)- ligands are located at the top and bottom of the central heptanuclear core. Variable temperature magnetic measurements indicate the presence of weak ferromagnetic CoII···CoII interactions (J = 3.53(6) cm-1) within the linear trinuclear CoII cluster. AC susceptibility measurements show that 1 is a field-induced single-molecule magnet (SMM) with τ0 = 8.2(7) × 10-7 s and Ueff = 11.3(4) K. The electrocatalytic hydrogen evolution reaction (HER) activity of 1 in homogeneous phase shows an overpotential of 455 mV, with a Faradaic efficiency of 81% and a TOF of 8.97 × 104 μmol H2 h-1 mol-1.

Metal-Organic Frameworks: Synthetic Methods and Potential Applications

Metal-organic frameworks represent a porous class of materials that are build up from metal ions or oligonuclear metallic complexes and organic ligands. They can be considered as sub-class of coordination polymers and can be extended into one-dimension, two-dimensions, and three-dimensions. Depending on the size of the pores, MOFs are divided into nanoporous, mesoporous, and macroporous items. The latter two are usually amorphous. MOFs display high porosity, a large specific surface area, and high thermal stability due to the presence of coordination bonds. The pores can incorporate neutral molecules, such as solvent molecules, anions, and cations, depending on the overall charge of the MOF, gas molecules, and biomolecules. The structural diversity of the framework and the multifunctionality of the pores render this class of materials as candidates for a plethora of environmental and biomedical applications and also as catalysts, sensors, piezo/ferroelectric, thermoelectric, and magnetic materials. In the present review, the synthetic methods reported in the literature for preparing MOFs and their derived materials, and their potential applications in environment, energy, and biomedicine are discussed.

Mono- and ditopic hydroxamate ligands towards discrete and extended network architectures

A family of mono- and ditopic hydroxamic acids has been employed in the synthesis and structural and physical characterisation of discrete (0D) and (1- and 2-D) extended network coordination complexes. Examples of the latter include the 1-D coordination polymer {[Zn(ii)(L₃H)₂]·2MeOH}_n (5; L₃H₂ = 2-(methylamino)phenylhydroxamic acid) and the 2-D extended network {[Cu(ii)(L₂H)(H₂O)(NO₃)]·H₂O}_n (5; L₂H₂ = 4-amino-2-(acetoxy)phenylhydroxamic acid). The 12-MC-4 metallacrown [Cu(ii)₅(L₄H)₄(MeOH)₂(NO₃)₂]·3H₂O·4MeOH (7) represents the first metal complex constructed using the novel ligand N-hydroxy-2-[(2-hydroxy-3-methoxybenzyl)amino]benzamide (L₄H₃). Variable temperature magnetic susceptibility studies confirm strong antiferromagnetic exchange between the Cu(ii) centres in 7. Coordination polymer 5 shows photoluminescence in the blue region (λ_PL∼ 421-450 nm) with a bathochromic shift of the emission (∼15-30 nm) from solution to the solid state.

Cobalt complexes of the chelating dicarboxylate ligand "esp": a paddlewheel-type dimer and a heptanuclear coordination cluster

The coordination chemistry of Co(ii) with the chelating dicarboxylate ligand esp (esp = α,α,α',α'-tetramethyl-1,3-benzenedipropionate) is explored. We report here the bimetallic paddlewheel-type dimer, Co2(esp)2(EtOH)2 (1), and a bowl-shaped, heptanuclear coordination cluster, Co7(OH)4(Hesp)2(esp)4(MeCN)2·4MeCN (2). Crystal structures of both complexes are reported as well as their magnetic properties, which indicate antiferromagnetic interactions among the Co(ii) ions.

New molecular heptanuclear cobalt phosphonates: synthesis, structures and magnetic properties

Synthesis, structures and magnetic properties (strong anisotropy, ferromagnetic and antiferromagnetic interactions) of novel {Co₇} homoleptic molecular cobalt phosphonates with a similar structure motif are described.

Highly efficient electrochemiluminescence based on 4-amino-1,2,4-triazole Schiff base two-dimensional Zn/Cd coordination polymers

ComplexesHL1andHL2and1–4exhibit a stronger ECL emission and complexes1–4exhibit higher stability.

Competitive coordination aggregation for V-shaped [Co3] and disc-like [Co7] complexes: synthesis, magnetic properties and catechol oxidase activity

The synthetic procedures, magnetic properties and catecholase-like activity of a V-shaped [CoII3L₄] and planar disc-like [CoII7L₆] complexes have been discussed.

Magnetism behaviours dominated by the interplay of magnetic anisotropy and exchange coupling in local CoII7 discs

Structure and magnetism of two CoII7 disc-based layers were reported. An asymmetric CoII7 core in the (4,4) layer exhibited single-molecule magnetic behavior. A highly symmetric C_2h CoII7 disc in the (3,6) sheet showed ferromagnetic exchange.

Asymmetric catalytic sulfoxidation by a novel VIV8 cluster catalyst in the presence of serum albumin: a simple and green oxidation system

Enantioselective oxidation of a series of alkyl aryl sulfides catalyzed by a novel VIV8 cluster is tested in an aqueous medium in the presence of serum albumin. The procedure is simple, environmentally friendly, selective, and highly reactive.

Microwave-assisted synthesis, structure and property of a spin-glass heptanuclear nickel cluster with 2-iminomethyl-6-methoxy-phenol

A new heptanuclear nickel cluster [Ni7(immp)6(OMe)6]·(ClO4)2 (1, Himmp is 2-iminomethyl-6-methoxy-phenol) has been synthesized through the microwave-assisted reaction of Ni(ClO4)2·6H2O with 2-hydroxy-3-methoxy-benzaldehyde and ammonium water in mixed solvent (acetonitrile: methanol = 1:1). Complex 1 was characterized by IR spectroscopy, elemental analysis and X-ray single-crystal diffraction. Magnetic property of 1 indicates the relaxation time τ 0 = 1.28 × 10–15 s and the energy barrier U eff / k B = 70.4 K, which is a spin glass.

Sulfonated Schiff base copper(ii) complexes as efficient and selective catalysts in alcohol oxidation: syntheses and crystal structures

Alcohol oxidation properties of four copper complexes (2–5) derived from the sulfonated Schiff base H₂L·3H₂O (1) are described. A quantitative conversion of 1-phenylethanol was obtained with 4 within 20 min of low power MW irradiation.

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

Recent and relevant examples of homo- and heterometallic complexes generated by Schiff base ligands derived from o-vanillin, as well as their properties, are discussed.

Microwave-assisted large scale synthesis of lanthanide metal–organic frameworks (Ln-MOFs), having a preferred conformation and photoluminescence properties

We have prepared 2 g Ln-MOF on a laboratory scale with high purity using microwave-assisted synthesis by changing the conformation of flexible ligand using Ln, which adopts only the preferred (energetically stable) conformation from green solvents (water and ethanol).

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

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.

Butterfly-like enantiomerically homochiral {CoII6CoIII4} clusters exhibiting both slow magnetic relaxation and ferroelectric property

A pair of butterfly-like enantiomerically homochiral [Co^II₆Co^III₄] clusters with both slow magnetic relaxation behaviour and ferroelectric property was synthesized.

Structural variation from heterometallic heptanuclear or heptanuclear to cubane clusters based on 2-hydroxy-3-ethoxy-benzaldehyde: effects of pH and temperature

Five novel clusters were reported, with results showing that pH and reaction temperatures have a key role in the self-assembly process.

A family of polynuclear cobalt complexes upon employment of an indeno-quinoxaline based oxime ligand

The employment of an indeno-quinoxaline based oxime ligand in cobalt chemistry afforded a new family of polynuclear cobalt clusters.

Synthesis and Crystal Structure of the Lead(II) Complex with 5-Hydroxyisophthalic Acid

The lead(II) Complex constructed with 5-hydroxyisophthalic acid, [Pb3(5-hipa)2]n•4H2O(1), (5-hipa = 5-hydro- xyisophthalic acid) has been synthesized by hydrothermal methods and structurally characterized by elemental analysis, IR and X-ray single crystal diffraction. In trinuclear symmetrical complex 1, Pb1 is four-coordinated, Pb2 and Pb3 are three-coordinated by 5-nitroisophthalic acid groups, respectively, which is further connected through intermolecular hydrogen bonds resulting in a three-dimensional (3D) network.