Magnetic properties of 4,4′-bipiperidinediium tetrahalocuprates: crystal structures of 4,4′-bipiperidinediium tetrabromocuprate(II) monohydrate and bis(4,4′-bipiperidinediium) hexabromodicuprate(I)

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.

Copper(II) Halide Salts with 1-(4′-Pyridyl)-Pyridinediium

The compounds [1,4′-bipyridine]-1,1′-diium [CuCl4] (1) and [1,4′-bipyridine]-1,1′-diium [CuBr4] (2) were prepared and their crystal structures and magnetic properties are reported. The compounds are isomorphous and crystallize in the monoclinic space group C2/c. The cation crystallizes in a two-fold disordered fashion with the terminal nitrogen and carbon atoms exhibiting 50% occupancies. This results in a crystal packing arrangement with significant hydrogen bonding that is very similar to that observed in the corresponding 4,4′-bipyridinediium complexes. Temperature dependent magnetic susceptibility measurements and room temperature EPR spectroscopy indicate the presence of very weak antiferromagnetic exchange. The data were fit to the Curie–Weiss law and yielded Weiss constants of −0.26(5) K (1) and −1.0(1) K (2).

X-ray structure and magnetic and fluorescence characteristics of new Cu(ii) complexes with Schiff bases derived from 2-(2-aminoethyl)pyridine and 2-hydroxy-1-naphthaldehyde; morphology and fluorescence of their thin films

Cu(ii) complexes with tridentate Schiff bases derived from 2-(2-aminoethyl)pyridine and 2-hydroxy-1-naphthaldehyde and COO-, Cl- and NO3- as ligands were obtained and characterized by crystal and molecular, spectroscopic (UV-Vis, fluorescence, IR, and EPR), magnetic and thermal methods. The X-ray crystal structure analysis revealed a distorted square planar geometry for [Cu(ii)(PEMN)CH3COO]CHCl3, 1, and [Cu(ii)(PEMN)Cl], 2, and a distorted square-pyramidal geometry for [Cu(ii)(PEMN)NO3], 3, corresponding to the values of EPR g-matrix diagonal components. The copper(ii) complexes exhibited fluorescence in solution in the range of 370-410 nm. Thin layers of the studied copper(ii) complexes were deposited on Si(111) by a spin coating method and studied by scanning electron microscopy (SEM/EDS), atomic force microscopy (AFM) and fluorescence spectroscopy. For copper(ii) layers (2/Si), the most intense fluorescence band from an intraligand and a d-d transition between 490 and 550 nm was observed.

The effects of protonated heterocyclic cations on the structural and magnetic properties of tetrachlorocuprate(ii) anions; X-ray, magnetochemical and EPR studies

The crystal and molecular structures and magnetic properties of two new complexes (HMepy)₂[CuCl₄]·2H₂O, 2, and (H₂Me₂ppz)[CuCl₄], 3, formed by tetrachlorocuprate(ii) anions and organic heterocyclic cations, have been determined by the analysis of their X-ray diffraction data, magnetic susceptibility behaviour and EPR spectral parameters.