Macrocyclic and Open‐Chain Cu II ‐4f (4f = Gd III , Ce III ) Complexes with Planar Diamino Chains: Structures and Magnetic Properties

Until now, the known structures of heterodinuclear Cu−Ln complexes involve compartmental Schiff‐base ligands with saturated diamino chains. We report here two Cu−Ln complexes (Ln = Gd or Ce) which are the first structurally characterized Cu−Ln entities involving S ‐methylisothiosemicarbazide as the diamino bridge, with open chain and macrocyclic ligands. The macrocyclic Cu−Gd entity is a well isolated dinuclear complex whereas two hydrogen bonds join together a pair of binuclear Cu−Ce complexes to give tetranuclear {Cu−Ce ··· Ce−Cu} entities. The Cu−Gd complexes [H = ‐J(S Cu S Gd )] exhibit ferromagnetic interactions between 5 and 5.5 cm −1 . Since the Cu−Ce complexes do not follow the Curie law due to the presence of orbital degeneracy, an analysis based on a simple spin‐only Hamiltonian is not possible. Nevertheless, the EPR spectra of the Cu−Ce complexes do confirm the existence of magnetic interactions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)