Slow magnetic relaxation in dinuclear dysprosium and holmium phenoxide bridged complexes: a Dy2 single molecule magnet with a high energy barrier

Dinuclear [M(H3L1,2,4)](2) (M = Dy, Dy-2; M = Ho, Ho-2) complexes were isolated from an heptadentate aminophenol ligand. The crystal structures of Dy-2 center dot 2THF, and the pyridine adducts Dy-2 center dot 2Py and Ho-2 center dot 2Py, show that the complexes are dinuclear, with unsupported double phenoxide bridges, and that the N4O4 environment of the Ln(III) centres is distorted triangular dodecahedral. The magnetic analysis of Dy-2 and Ho-2 shows that Dy-2 is a single molecular magnet (SMM), with a thermal-activated zero-field effective energy barrier (U-eff) of 367.7 K, the largest barrier shown by double phenoxide-bridged dinuclear dysprosium complexes to date. Ho-2 is one of the scarce dinuclear complexes showing frequency-dependence for the out-of-phase component of susceptibility, although it does not even show field-induced SMM behaviour above 2 K. Ab initio calculations were performed in order to shed light on the magnetic dynamics of the complexes, and these studies support the experimental magnetic results.

Automated summary

Dinuclear complexes [M(H3L1,2,4)](2) (M = Dy, Dy-2; M = Ho, Ho-2) were isolated from a heptadentate aminophenol ligand, with the dysprosium complex showing the largest energy barrier to date for this type of double phenoxide-bridged complexes. The holmium complex exhibits frequency-dependence but does not display field-induced SMM behavior above 2 K. Ab initio calculations were used to understand the magnetic properties of the complexes, which supported the experimental magnetic results.