Hybrid Cu-Containing Compounds Based on Lacunary Strandberg Anions: Synthesis under Mild Conditions, Crystal Structure, and Magnetic Properties

A one-pot reaction of a copper source (metallic powder Cu⁰ or Cu²⁺ salts) and bpy (bpy = 2,2'-bipyridine) in the presence of (NH₄)₂HPO₄ and (NH₄)₆Mo₇O₂₄·4H₂O yields heterometallic hybrid compounds of the general type {[Cu(bpy)_n(H₂O)_m]_p[P₂Mo_xO_y]}. The structures exhibit a number of phosphomolybdate POMs including not only a common Strandberg anion [P₂Mo₅O₂₃]^6- but also its unprecedented bi- and trilacunary derivatives [P₂Mo₃O₁₈]^8- and [P₂Mo₂O₁₅]^8-. The structural determinants including the metal source (copper powder vs copper salts), counterion of the salts, and stoichiometry of the reagents were examined. An ex situ EPR study revealed the formation of different Cu^II complexes in the reaction mixture depending on the copper precursor. The obtained compounds have been found to possess selectivity toward the sorption of methylene blue in a mixture of organic dyes. DC magnetic measurements of 1-3 indicate rather strong antiferromagnetic metal-metal exchange interactions. Compound 1 exhibits field-induced slow magnetic relaxation in AC magnetic measurements, which is a rarely observed phenomenon among Cu(II) complexes.

Molecular and heterogeneous water oxidation catalysts: recent progress and joint perspectives

The recent synthetic and mechanistic progress in molecular and heterogeneous water oxidation catalysts highlights the new, overarching strategies for knowledge transfer and unifying design concepts.

Hybrid compound based on diethylenetriaminecopper(ii) cations and scarce V-monosubstituted β-octamolybdate as water oxidation catalyst

Herein, we report on a new hybrid compound (NH₄){[Cu(dien)(H₂O)₂]₂[β-VMo₇O₂₆]}·1.5H₂O (1), where dien = diethylenetriamine, containing an extremely rare mixed-metal pseudo-octamolybdate cluster. An ex situ EPR spectroscopy provided insights into the formation of paramagnetic species in reaction mixture and in solution of 1. The magneto-structural correlations revealed weak antiferromagnetic exchange interactions between the [Cu(dien)]²⁺ cations transmitted by intermolecular pathways. The cyclic voltammetry showed the one-electron process associated with the Cu³⁺/Cu²⁺ oxidation followed by the multi-electron catalytic wave due to water oxidation with a faradaic yield of 86%. The title compound was thus employed in homogeneous water oxidation catalysis using tris(bipyridine)ruthenium photosensitizer. At pH 8.0, efficiency of the catalytic system attained 0.19 turnovers per second supported by the relatively mild water oxidation overpotential of 0.54 V.

A new hybrid compound (NH₄){[Cu(dien)(H₂O)₂]₂[β-VMo₇O₂₆]}·1.5H₂O was employed in homogeneous water oxidation catalysis. At pH 8.0, its efficiency attains 0.19 turnovers per second, supported by the relatively mild water oxidation overpotential of 0.54 V.

Extending the structural landscape of Mo(vi) hydrazonato inorganic–organic POM-hybrids: an experimental and computational study

Novel Mo(vi) hydrazonato octamolybdate and hexamolybdate hybrids have been synthesized and structurally characterized. Quantum chemical calculations have been applied to determine the possibility of developing the covalently anchored hybrids.

Stabilisation of high-valent Cu3+ in a Keggin-type polyoxometalate

An unprecedented Keggin-type Cu3+-containing polyoxometalate Cs3H[CuIIIPW11O39]·11H2O (1-Cs) was successfully synthesised through a newly-developed Ag+-promoted chemical oxidation by S2O82- in aqueous medium and systematic characterisation with powder XRD, XPS, IR, UV-vis and 31P NMR spectroscopies proves the effective stabilisation of a high-valent Cu3+ center by a mono-lacunary Keggin type polyoxometalate ligand.