A single molecule magnet (SMM) with a helicate structure

The X-ray structure determination of [L2Cu2Gd2(NO3)(6)(H2O)(2)]-(0.5H(2)O) (L = bis-[(2-hydroxy-3-ethoxyphenyl) methylene]4,4'- methylenedianiline) confirms the existence of a tetranuclear double-stranded homotopic and unsaturated helicate. In each Cu - Gd pair, the reduced Cu center dot center dot center dot Gd distance allows ferromagnetic Cu - Gd superexchange interactions through two phenoxo oxygen atoms. Replacement of gadolinium ions by terbium ions yields the first example of a helicate behaving as a single molecule magnet (SMM).