Series of edge-sharing bi-triangle Ln4 clusters with a μ4-NO3− bridge: syntheses, structures, luminescence, and the SMM behavior of the Dy4 analogue

Abstract

A series of Ln₄ clusters, [Ln₄L₂(μ₃-OH)₂(μ₄-NO₃)(NO₃)₄(OCH₃)(H₂O)]·xMeCN·yMeOH (Ln = Gd (1), Tb (2), Dy (3), Ho (4), Er (5), Yb (6), L = 2-{[2-(2-hydroxy-ethoxy)-ethylimino]-methyl}-6-methoxyphenol), have been synthesized by the reaction of Ln(NO)₃ and a Schiff-base ligand formed in situ. The six complexes display similar structures, with an overall metal core comprising two edge-sharing triangular Ln₃ units linked by a μ₄-NO₃⁻ bridge. The luminescence spectrum of complex 2 shows the characteristic emission of the Tb^III ions. The magnetic susceptibility studies reveal that the Ln^III ions are very weakly interacting in all six compounds. Frequency dependence of the ac-susceptibility was found for 3, suggesting a typical single-molecule magnet (SMM) behavior with an anisotropic barrier of 28 K.