Unprecedented tetranuclear complexes with "weighing balance shaped" topology: single crystal structures, unusual EPR spectra, magnetic properties and antioxidant activity.

Using the 2-hydroxy-N'-[(E)-phenyl(pyridin-2-yl)methylidene]benzohydrazide ligand and dicarboxylate anions (succinate and malonate), two new copper(ii) complexes of formula [Cu(μ-L)(μ-CH(COO))(HO)](NO)·4HO (1) and [Cu(μ-L)(μ-CH-CH(COO))(HO)](NO)] (2) have been synthesized and characterized by single crystal X-ray diffraction. Complexes 1 and 2 contain a dicarboxylate bridged tetranuclear Cu(ii) cationic unit with "weighing balance shaped" topology. These compounds have also been studied by variable temperature magnetic susceptibility measurements, X-band EPR spectroscopy and electrochemistry.

Classical hydrogen bonding and stacking of chelate rings in new copper(ii) complexes.

Three new copper(ii) complexes, viz., [Cu(L)(NO)(HO)]HO 1, [Cu(L)(HO)]NO2 and [Cu(L)(pyrazine)](ClO)·4HO 3, were prepared using a biomimetic synthesis strategy [HL = 4-chloro-2-{(E)-[2-(pyridin-2-yl)hydrazinylidene]methyl}phenol]. Structural characterization revealed very different local geometries around copper(ii) ions, being square pyramidal for mononuclear complexes (τ = 0.