Synthesis,spectroscopy, electrochemistry and structural determination of asymmetric cobalt(III) Schiff base complexes

The [CoL(PR₃)(CH₃OH)]ClO₄ (where L = MeSalophen, 5-NO₂MeSalophen, 5-BrMeSalophen, 5-MeOMeSalophen, 4-MeOMeSalophen, 3-MeOMeSalophen and R=Ph or Bu) complexes were synthesized and also characterized by FTIR, UV–Vis, ¹H NMR and ¹³C NMR spectroscopies. The absorptions between 550 and 750 nm for the complexes are attributed to d–d transitions. Electrochemical properties of the complexes were examined by means of cyclic voltammetry. The anodic peak potentials were more positive in the following trend NO₂ > Br > H > MeO and are in accordance with electronic effects of the substituents. The crystal structure of [Co(5-NO₂MeSalophen)(PBu₃)(CH₃OH)]ClO₄ and [Co(5-BrMeSalophen)(PPh₃)(CH₃OH)]ClO₄ was determined by single-crystal X-ray diffraction. They showed six-coordinated pseudo-octahedral geometries in which equatorial planes are formed by the O(1), O(2), N(1) and N(2) atoms of the Schiff base and the axial positions were occupied by PR₃ and methanol.