Macrocyclic CuII4 and CuII2MII complexes. Structure of a heterotrinuclear CuII2ZnII complex exhibiting a helical twist

Abstract

Three heterotrinuclear complexes [Cu₂Zn(HL)][CIO₄]₃·3H₂O 1, [Cu₂Mg(HL)][CIO₄]₃·2H₂O 2 and [Cu₂Mg(HL)][NO₃]₃·3H₂O 3 and two tetranuclear complexes [Cu₄L][CIO₄]₄·4H₂O 4 and [Cu₄L(µ₃-OH)][CIO₄]₃·MeOH 5 have been synthesized from a 38-membered macrocycle (H₄L) having eight amine and four phenol functionalities. The compounds have been characterized on the basis of IR, UV/VIS and ESR spectroscopy and magnetic susceptibility measurements. Their redox chemistry has been studied by cyclic voltammetry and differential pulse voltammetry. The crystal structure of 1 has been determined. The two copper centers have N₂O₂ square-planar co-ordination environments and the zinc has a trigonal-bipyramidal geometry with N₃O₂ donors; one of the copper(II) ions is bridged to the zinc(II) ion by two phenolate oxygens. The cation in 1 has a helically twisted configuration.