Magnetic and Structural Studies of Copper-Lanthanoid Complexes; the Synthesis and Structures of New Cu3Ln Complexes of 6-chloro-2-Pyridone (Ln = Gd, Dy and Er) and Magnetic Studies on Cu2Gd2, Cu4Gd2 and Cu3Gd Complexes

The synthesis and structural characterisation of three copper–lanthanoid complexes are reported. The compounds, of general formula [Cu3M(chp)8(NO3)(S)] [M = Gd, S = H2O in 2; M = Dy, S = H2O in 3; M = Er, S = (H2O)0.5(MeOH)0.5 in 4; chp = anion of 6‐chloro‐2‐pyridone], are made by reaction of [Cu2(chp)4] (1) with the hydrated lanthanoid nitrate salt in methanol. Structural studies reveal the three copper atoms lie in an approximate hemisphere about a central lanthanoid atom. Magnetic studies on 2 and two further Cu–Gd complexes show ferromagnetic coupling between the 3d and 4f metals. Consideration of these results along with magnetic data previously reported for Cu–Gd compounds leads to a correlation between the magnitude of this exchange coupling and the exponential of the Cu…Gd distance. This is the first magneto‐structural correlation reported for mixed d‐block/f‐block metal complexes. The first magneto–structural correlation proposed for mixed d‐block/f‐block complexes indicates an exponential dependence of the magnitude of the exchange coupling on the Cu … lanthanoid distance. This relationship is derived from the magnetic behaviour of three new copper–lanthanoid complexes bridged by pyridone ligands, such as that shown on the right, and from that of related species.