Studies involving nitrogen–oxygen donor macrocyclic ligands. Interaction of copper(II) with new O2N3-donor macrocycles and the X-ray analysis of aqua(1,12,16-triaza-3,4:9,10-dibenzo-5,8-dioxacyclo-octadecane)copper(II) diperchlorate hydrate

Abstract

The interaction of Cu²⁺ with three new O₂N₃-donor macrocycles has been investigated. Complexes of the type CuL(ClO₄)₂.nH₂O and CuLX(ClO₄).nH₂O (where L = macrocycle, X = Cl or Br, and n= 0, 1, or 2) have been isolated. Conductance studies indicate that the halide ions in the latter complexes are co-ordinated in dimethyl sulphoxide. All complexes show the expected magnetic moments for Cu²⁺ with S=½. Potentiometric titration studies in 95% methanol (I= 0.1 mol dm^–3, [NMe₄]Cl) indicate that the following equilibria involving Cu²⁺ occur : Cu²⁺+ L ⇌ CuL²⁺ and Cu²⁺+ HL⁺⇌ Cu(HL)³⁺ and the respective formation constants have been determined. The X-ray structure of [CuL³(OH₂)][ClO₄]₂·H₂O indicates that this complex has a pseudo-square-planar co-ordination geometry with the co-ordination sphere consisting of the three nitrogen atoms of the macrocycle [Cu–N, 1.97(3)–2.07(2)Å] together with an oxygen from water [Cu–O, 1.96(2)Å]. The ether oxygen donors of the macrocycle do not co-ordinate. Crystals are monoclinic, with space group P2₁/c, a= 16.856(7), b= 10.717(4), c= 16.738(18)Å, β= 110.59(5)°, and Z= 4, R being 0.12 for 1 044 ‘observed’ reflections.