Synthesis and X-ray structural characterization of sterically hindered bis(3,5-di-tert-butylsalicylaldiminato)Cu(II) complexes

Abstract

Bis(3,5-di-tert-butylsalicylaldiminato)Cu(II) complexes were prepared in high yields from a sterically hindered 3,5-di-tert-butylsalicylaldehyde and a variety of amines using three synthetic approaches. They were all thoroughly characterized by various spectroscopic methods (UV–Vis, IR, EPR and EI-MS). Crystal structures of seven complexes determined by X-ray crystallography show the Cu ion in a N2O2 coordination environment and a tetrahedrally distorted square–planar geometry. The UV–Vis and EPR results indicated that the complexes have the same geometry also in solution. In two solid state structures of the complexes the ligands have obtained an unusual cis-orientation whereas the rest of the complexes are trans-isomers. Computational studies carried out by the density functional theory method verified that in the case of complex with N-alkyl fragment the preferred isomer is trans, while the opposite behavior is observed for the complex with N-phenyl substituent.