Synthesis, X-ray crystal structure, and electrochemistry of copper(II) complexes of a new tridentate unsymmetrical Schiff base ligand and its hydrolytically rearranged isomer

Article abstract of DOI:10.1016/j.ica.2011.12.025

A new unsymmetrical Schiff base ligand HL¹, HBacabza, and its copper(II) complexes [Cu₂L¹₂(OAc)₂] (1) and [Cu₂L²₂(N₃) ₂]·2H₂O (2) with HBacabza = 3-(2-aminobenzylimino)- 1-phenylbutan-1-one as HL¹ and its hydrolytically rearranged isomer 3-(2-aminomethylphenyleneimino)-1-phenylbutan-1-one as HL², have been synthesized and characterized by elemental analyses and spectroscopic methods. The rearrangement of HL¹ to HL² occurs in a hydrolysis-recondensation process in the reaction of HL¹ with Cu(ClO₄)₂·6H₂O and NaN₃. The crystal structures of the ligand and its complexes have been determined by single crystal X-ray diffraction. The deprotonated Bacabza^- coordinates to the metal center as a tridentate ligand. The acetate anion coordinates through one oxygen atom in complex 1 leading to a mono-atomic acetate oxygen-bridging dimeric copper(II) complex. Similarly, the azide anion coordinates through one nitrogen atom in complex 2 leading to a mono-atomic azide nitrogen-bridging dimeric copper(II) complex. The copper(II) ions adopt a distorted square pyramidal (4 + 1) coordination in these two complexes. The cyclic voltammetric studies of these complexes in N,N-dimethylformamide indicate that the reduction process corresponding to Cu^II/Cu^I is electrochemically irreversible in complex 1, presumably due to the structural changes during the course of redox reaction, and quasi-reversible in complex 2.