Synthesis and characterization of oxamido-bridged pentanuclear [Cu(II)](4)Ln(III) complexes with a [14]N-4 macrocyclic oxamide

Seven novel oxamido-bridged pentanuclear copper(II)-lan-thanoid(III) comple xes of a macrocyclic oxamide have been prepared by the strategy of "complex es as ligands" and characterized by elemental analyses, conductivity measur ements, IR and UV-Visable spectra. The complexes are of formula [(CuL)(4)Ln ](ClO4)(3). xH(2)O [Ln = La(III), Pr(III), Nd(III), Sm(Ill), Gd(III), Dy(II I) and Er(III), x = 1, 2 or 3, H2L = 2,3-dioxo-5,6:13,14-dibenzo-7,12-bis(e thoxycarbonyl)-1,4,8,11-tetraazacyclotetradeca-7,11-diene]. The temperature dependence of the magnetic susceptibility of the [Cu4Gd] complex has been investigated and revealed ferromagnetic interaction between the Cu(II) and Gd(III) ions with the exchange integral J(CuGd) 0.76 cm(-1) (based on (H) o ver cap = -2J Sigma(s) over cap (i)(s) over cap (j)).