Bis-dinuclear (Cu-Gd)2 complexes with a probable helicate structure

Two ligands have been designed to simultaneously favour complexation of 3d and 4f metal ions and the formation of helical structures. This synthetic strategy has allowed the isolation of two bis-dinuclear (Cu-Gd)(2) complexes [(L2Cu2Gd2)-Cu-i(NO3)(6)] derived from 3-alkoxysalicylaldehyde and 4,4'-diaminodiphenylmethane. The magnetic data shows that both bis-dinuclear complexes behave as two practically independent (Cu-Gd) pairs, each presenting a ferromagnetic interaction (J=4.6 cm(-1)). Very weak additional antiferromagnetic interactions, probably originating from intra- and/or intermolecular. stackings, are suggested by the decrease in chi(M)T below 8 K.