Strategy for the Rational Design of Asymmetric Triply Bridged Dinuclear 3d-4f Single-Molecule Magnets

Three triply bridged M(II)-Dy(III) dinuclear complexes, [Ni(mu-L)(mu-OAc)Dy(NO(3))(2)] 1, [Zn(mu-L)(mu-OAc)Dy(NO(3))(2)] 2, and [Ni(mu-L)(mu-NO(3))Dy(NO(3))(2)]center dot 2CH(3)OH 3 were prepared with a new and flexible compartmental ligand, N,N',N ''-trimethyl-N,N ''-bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylene triamine (H(2)L), containing N(3)O(2)-inner and O(4)-outer coordination sites. These complexes have diphenoxo/acetate (1 and 2) or diphenoxo/nitrate (3) asymmetric bridging fragments. Compounds 1 and 3 exhibit ferromagnetic interaction between Ni(2+) and Dy(3+) ions and frequency dependence of the out-of-phase (chi '' M) alternating current (ac) susceptibility signal characteristic of single-molecule-magnet behavior. The energy barriers Delta/k(B) for compound 3 under zero and 1000 Oe applied direct current (dc) magnetic fields were estimated from the Arrhenius plots to be 7.6 and 19.1 K, respectively.