Structural, MALDI-TOF-MS, Magnetic and Spectroscopic Studies of New Dinuclear Copper(ii), Cobalt(ii) and Zinc(ii) Complexes Containing a Biomimicking μ-OH bridge

Abstract

The Py(2)N(4)S(2) octadentate coordinating ligand afforded dinuclear cobalt, copper and zinc complexes and the corresponding mixed metal compounds. The overall geometry and bonding modes have been deduced on the basis of elemental analysis data, MALDI-TOF-MS, IR, UV-vis and EPR spectroscopies, single-crystal X-Ray diffraction, conductivity and magnetic susceptibility measurements. In the copper and zinc complexes, a μ-hydroxo bridge links the two metal ions. In both cases, the coordination geometry is distorted octahedral. Magnetic and EPR data reveal weakly antiferromagnetic high spin Co(II) ions, compatible with a dinuclear structure. The magnetic characterization of the dinuclear Cu(II) compound indicates a ferromagnetically coupled dimer with weak antiferromagnetic intermolecular interactions. The intra-dimer ferromagnetic behaviour was unexpected for a Cu(II) dimer with such μ-hydroxo bridging topology. We discuss the influence on the magnetic properties of non-covalent interactions between the bridging moiety and the lattice free water molecules.

Transition from isolated to interacting copper(ii) pairs in extended lattices evaluated by single crystal EPR spectroscopy

“…4,[17][18][19] The electronic properties of these metal systems are determined by the isotropic exchange interaction, which couples the two individual electron spins (S = 1/2) to yield singlet (S = 0) and triplet (S = 1) states, and other interactions such as anisotropic and antisymmetric exchange and dipolar magnetic coupling. 4,[17][18][19] The electronic properties of these metal systems are determined by the isotropic exchange interaction, which couples the two individual electron spins (S = 1/2) to yield singlet (S = 0) and triplet (S = 1) states, and other interactions such as anisotropic and antisymmetric exchange and dipolar magnetic coupling.…”

“…Among the vast number of studies on paramagnetic transition metal ion complexes, the study of dinuclear Cu(II) compounds (S = 1/2 spin pair) has been essential in the development of molecular magnetism. 4,[17][18][19] The electronic properties of these metal systems are determined by the isotropic exchange interaction, which couples the two individual electron spins (S = 1/2) to yield singlet (S = 0) and triplet (S = 1) states, and other interactions such as anisotropic and antisymmetric exchange and dipolar magnetic coupling. 20 The isotropic exchange interaction (H ex = −JS 1 •S 2 ) splits the singlet from the triplet state of the dimer by an energy amount J, whereas the remaining interactions can remove the three-fold degeneration of the triplet state even in zero magnetic field (ZFS).…”

Synthesis, structure, and characterisation of a ferromagnetically coupled dinuclear complex containing Co(ii) ions in a high spin configuration and thiodiacetate and phenanthroline as ligands and of a series of isomorphous heterodinuclear complexes containing different Co : Zn ratios

“…It is unclear how the bridging topology determines the antiferro or ferromagnetic nature of the interaction. 26,37,39,47,[49][50][51][52] Additional interest in Co(II) dinuclear complexes is due to their presence in metallohydrolases involved in the hydrolysis of peptide bonds (e.g. in methionine aminopeptidase) and, hence, their potential use as therapeutic agents.…”

“…19 The most common experimental techniques for characterising the electronic and magnetic properties of high spin Co( ii ) ions are spectroscopic methods such as UV-vis absorption, magnetic circular dichroism, paramagnetic nuclear magnetic resonance, electron paramagnetic resonance (EPR), and electron-nuclear double resonance, and magnetic techniques such as magnetic susceptibility and magnetisation measurements. 20–40 Characterisation of high spin Co( ii ) ion complexes in different coordination environments with these techniques showed that they present g-values for the S = 3/2 multiplet in the range of 2.1–2.8, and zfs usually greater than 50 cm −1 for hexacoordinated compounds, between 20–50 cm −1 for pentacoordinated compounds and less than 13 cm −1 for tetracoordinated compounds, 41 although some exceptions have been reported. 42–46 Furthermore, the exchange interactions that couple mononuclear Co( ii ) centres in extended lattices are usually below ∼3 cm −1 , and hence usually not detected or poorly discriminated with the most usual experimental techniques, with the only exception being EPR.…”

Spectroscopic and photophysical studies of a naphthalene-based emissive probe for metal cations

“…Following our research interest on the design of new emissive compounds [20,[24][25][26][27] and metal complexes [28][29][30], in this work, the photophysical properties of another symmetric probe L, with two naphthalene units in the extreme as well, was described together with its ) were mixed in absolute ethanol. After 4h, the solvent was partially removed to ca.…”