Synthesis, spectroscopy and electrochemical behaviors of nickel(II) complexes with tetradentate shiff bases derived from 3,5-Bu(2)(t)-salicylaldehyde.

Nickel(II) complexes of a series of N,N'-polymethylenebis(3,5-Bu(2)(t)-salicylaldimine) ligands containing 2,4-di-Bu(2)(t)-phenol arms, NiL(x), were synthesized and their spectroscopic and redox properties were examined. The UV-vis, (1)H NMR spectroscopic and magnetic results indicate that complexes NiL(1)-NiL(4) unlike NiL(5) and NiL(6) have a square-planar structure in the solid state and in solution. Cyclic voltammograms of NiL(x) (x=1-4) complexes displayed two-step oxidation processes. The first oxidation peak potentials of all Ni(II) complexes corresponds to the reversible one-electron oxidation process of the metal center, yielding Ni(III) species. The second oxidation peak of the complexes was assigned as the ligand based oxidation generating a coordinated phenoxyl radical species.