Efficient stabilization of copper(III) in tetraaza pseudo-macrocyclic oxime-and-hydrazide ligands with adjustable cavity size.

Substitution of the amide donors in open-chain {2N(oxime), 2N(amide)} ligands by hydrazide donors gives new pseudo-macrocyclic copper complexes that show a significant decrease of the Cu(3+/2+) redox potentials in both mono- and polynuclear systems, thus demonstrating a pronounced capacity of such ligand systems to efficiently stabilize the trivalent copper.

Effect of metal ionic radius and chelate ring alternation motif on stabilization of trivalent nickel and copper in binuclear complexes with double cis-oximato bridges.

Oxime ligands are able to form stable binuclear species with copper(II) ions in aqueous solution. They also have a strong tendency to decrease the Mn+/(n-1)+ redox potentials of the central ions. Ligands possessing the hydroxyimino groups together with other powerful sigma-donor groups can be very efficient chelating agents able to facilitate the stabilisation of high oxidation states of 3d-metals.