Monomeric and dimeric copper(II) complexes of a redox active Schiff base ligand bis(2,5-dihydroxyacetophenone) ethylenediamine

Abstract

Monomeric and dimeric copper(II) complexes with a tetradentate Schiff base, bis(2,5-dihydroxyacetophenone) ethylenediamine have been synthesized and characterized by spectroscopic techniques. Solution EPR of the complexes in DMSO shows less than four g | lines and a broadening of the g ⊥ component suggesting a lowered site symmetry clear five-line pattern emerges with A N ⋍ 15 ± 1 G, supporting the binding of a tetradentate ligand with two N and two O donor sites. For the monomeric complexes g | is in the range of 2.18–2.20, suggesting a near square-planar arrangement of N 2O 2 donor groups (θ) = 0). The complexes exhibit a visible band with λ max in the 500–600 nm region in solution. This is found to split into two components in the solid state reflectance spectra. The spectral data suggests a distorted tetragonal geometry for copper(II) ions in the present complexes. The copper complexes prepared by using CuCl 2 analyses for the stoichiometry 2 Cu : 1 DAen, i.e. [Cu(DAen)CuCl 2], suggesting the formation of a dimeric species. This is supported by low λ eff of 1.49 B.M., implying an exchange coupled complex. Further, the coupling constant evaluated for the peaks involved in g | region is 118.75 G, a value which is nearly half of that found for the monomeric complexes.