Synthesis and characterization of homo-dinuclear complexes [M2(dea)2(H2O)4], [M2(dea)2(Bipy)2] and [Fe2(dea)2(H2O)2(Cl)2] (M = Co, Ni or Cu; H2dea = diethanolamine): 57Fe Mössbauer and electrochemical investigations

The homo-dinuclear title complexes were prepared and characterized employing analytical and spectral techniques. The ligand binds the metal ions as a bidentate dianionic (dea2−) chelating moiety forming MOM bridges to result in homo-dinuclear complexes. The electronic (ligand field) spectral data suggest a hexa-coordinate environment around high spin state of metal ion. EPR data of Cu(II) complexes confirm a distorted octahedral geometry. The observed quadrupole splitting and the relevant parameters δ, ΔEQ and the line width in the 57Fe Mössbauer spectrum of the iron complex are consistent with a high spin state of Fe(III) in a distorted octahedral environment and the presence of Kramer’s double degeneracy. The CV data suggest probable formation of quasi reversible redox couples CuII/I or FeIII/II in aqueous solutions of the respective complexes.

► Homo-dinuclear complexes were prepared and characterized. ► EPR and ligand field spectra indicated a high-spin state of metal ion with hexa-coordinate environment. ► CV studies indicated the presence of quasi-reversible redox couples in solution. ► The 57Fe-Mössbauer spectral investigations of Fe(III) complex have also been performed.