Mononuclear Lanthanide Single Molecule Magnets Based on the Polyoxometalates [Ln(W5O18)2]9− and [Ln(β2-SiW11O39)2]13−(LnIII = Tb, Dy, Ho, Er, Tm, and Yb)
journal contributionposted on 20.04.2009, 00:00 by Murad A. AlDamen, Salvador Cardona-Serra, Juan M. Clemente-Juan, Eugenio Coronado, Alejandro Gaita-Ariño, Carlos Martí-Gastaldo, Fernando Luis, Oscar Montero
The first two families of polyoxometalate-based single-molecule magnets (SMMs) are reported here. Compounds of the general formula [Ln(W5O18)2]9− (LnIII = Tb, Dy, Ho, and Er) and [Ln(SiW11O39)2]13− (LnIII = Tb, Dy, Ho, Er, Tm, and Yb) have been magnetically characterized with static and dynamic measurements. Slow relaxation of the magnetization, typically associated with SMM-like behavior, was observed for [Ln(W5O18)2]9− (LnIII = Ho and Er) and [Ln(SiW11O39)2]13− (LnIII = Dy, Ho, Er, and Yb). Among them, only the [Er(W5O18)2]9− derivative exhibited such a behavior above 2 K with an energy barrier for the reversal of the magnetization of 55 K. For a deep understanding of the appearance of slow relaxation of the magnetization in these types of mononuclear complexes, the ligand-field parameters and the splitting of the J ground-state multiplet of the lanthanide ions have been also estimated.