Single-Molecule Magnet of a Tetranuclear Dysprosium Complex Disturbed by a Salen-Type Ligand and Chloride Counterions

A series of three salen-type lanthanide complexes, e.g., [Dy-4(L)(2)(HL)(2)Cl-2(mu(3)-OH)(2)](2)Cl-2(OH)(2) 3CH(3)CH(2)OH H2O (1) and [Ln(4)(L)(2)(HL)(2)Cl-2(mu(3)-OH)(2)]Cl-2 5CH(3)OH 4CH(2)Cl(2) (Ln = Tb-III, 2; HoIII, 3) have been isolated by the reactions of H2L (H2L = N,N'-bis(3-methoxysalicylidene)cyclohexane-1,2-diamine) with LnCl(3) 6H(2)O. X-ray crystallographic analysis reveals that all complexes 1-3 are isostructural, in which four Ln ions and eight O atoms form the distorted defective dicubane {Dy4O8} cores. Magnetic studies indicate that complex 1 exhibits two slow magnetic relaxation processes with effective energy barrier U-eff = 55.71 K under a zero direct-current field, which is attributed to the two coordination geometries of the Dy-III ions with a salen-type ligand and coordination of a chloride counterion. It represents the highest energy barrier among the salen-type tetranuclear lanthanide single-molecule magnets.