Trinuclear [Co2III-LnIII] (Ln=Tb, Dy) Single-Ion Magnets with Mixed 6-Chloro-2-Hydroxypyridine and Schiff Base Ligands

The Schiff base ligand N1,N3-bis(3-methoxysalicylidene)di-ethylenetriamine (H(2)valdien) and the co-ligand 6-chloro-2-hydroxypyridine (Hchp) were used to construct two 3d-4f heterometallic single-ion magnets [Co2Dy(valdien)(2)(OCH3)(2)(chp)(2)]center dot ClO4 center dot 5H(2)O (1) and [Co2Tb(valdien)(2)(OCH3)(2)(chp)(2)]center dot ClO4 center dot 2H(2)O center dot CH3OH (2). The two trinuclear [Co(2)(III)Ln(III)] complexes behave as a mononuclear Ln(III) magnetic system because of the presence of two diamagnetic cobalt(III) ions. Complex 1 has a molecular symmetry center, and it crystallizes in the C2/c space group, whereas complex 2 shows a lower molecular symmetry and crystallizes in the P2(1)/c space group. Magnetic investigations indicated that both complexes are field-induced single-ion magnets, and the Co-2(III)-Dy-III complex possesses a larger energy barrier [74.1(4.2) K] than the Co-2(III)-Tb-III complex [32.3(2.6) K].