Transition metal ions as cores in the construction of an unprecedented large macrocycle

New macrocyclic complexes have been prepared by reacting diethylenetriamine, benzil and a metal ion [cobalt(II), nickel(II) and copper(II)] in a 2:2:1 ratio in MeOH. The complexes were characterized by elemental analysis, spectroscopic data (u.v., i.r. and e.p.r.) magnetic susceptibility and conductivity measurements and are probably covalent. The metal ions are paramagnetic in a free spin state and appear to possess a slightly distorted octahedral geometry. A cyclic voltametric study on the copper complex indicates a reversible redox couple (Cu-II reversible arrow Cu-I, E degrees = -0.48 V) in DMSO, which means that the macrocycle is capable of stabilizing the Cu-II reversible arrow Cu-I process.