Magnetic studies of copper(II) complexes of benzoic acid and substituted benzoic acids

Abstract

A study of the magnetic properties (80–310 K) of the complexes [Cu₃(O₂CC₆H₄R)₆]·3,6NH-od (R = H, m-Me, or o-NO₂; 3,6NH-od = 3,6-diazaoctane-1,8-diamine) indicates the presence of ferromagnetic interactions. In the cases of R = H and m-Me, feeble ferromagnetism appears in the range 80–150 K. The o-nitrobenzoato-complex shows only antiferromagnetic interactions leading to diamagnetism in the 80–150 K region. Comparison of the experimental and calculated susceptibilities with the Bleaney–Bowers model with –2J= 289.2 cm^–1 for R = H. 311.4 cm^–1 for R =m-Me, and 265.6 cm^–1 for R =o-NO₂(in each case g= 2.19 and N= 60 c.g.s. units), indicates that the complexes are polymeric with three binuclear units of benzoatocopper(II) joined by two 3,6NH-od molecules. A spectral band in the 333–425 nm region indicates the presence of metal–metal interactions. Lowering of a band at 1 695cm^–1 to 1 620–1 640 cm^–1 is indicative of carboxylate bridging, and a band in the 800–820 cm^–1 region is attributed to M–N co-ordination.