Structure and magnetic properties of new dinuclear copper(II) complexes bridges by chloranilate or bromanilate dianions

Dinuclear copper(II) complexes bridged by chloranilate (C1DHBQ^2-) or bromanilate (BrDHBQ^2-) dianions and end-capped with 2,2′-dipyridyl (bpy) or 1,10-phenathroline (phen), [Cu₂(L)₂(XDHBQ)]Y₂ (L = bpy or phen; X = Cl or Br; Y = ClO₄^- or PF₆^-), were prepared as solvated (H₂O or CH₃OH) or unsolvated forms. The complex [Cu₂(bpy)₂(ClDHBQ)](PF₆)₂·2CH₃OH has been characterized by X-ray crystallography. The crystal consists of a dinuclear cation {Cu₂(bpy)₂(ClDHBQ)(CH₃OH)₂}²⁺ and hexafluorophosphate ions. The two copper(II) ions are bridged by ClDHBQ^2- with a Cu---Cu separation of 7.661 Å. The configuration about each copper atom is square pyramidal, with two oxygens of ClDHBQ^2- and two nitrogens of bpy at the basal plane and the methanol oxygen at the apex. Magnetic studies of the complexes in the temperature range 4.2-300 K reveal a significant antiferromagnetic spin-exchange through the XDHBQ bridge. The exchange integrals are evaluated as - J = 11.7-16.3 cm^-1 based on H = -2JŜ₁Ŝ₂.