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

Abstract

Dinuclear [M(H3L1,2,4)]2 (M = Dy, Dy2; M = Ho, Ho2) complexes were isolated from an heptadentate aminophenol ligand. The crystal structures of Dy2∙2THF, and the pyridine adducts Dy2∙2Py and Ho2∙2Py, show that the complexes are dinuclear, with unsupported double phenoxide bridges, and that the N4O4 environment of the LnIII centres is distorted triangular dodecahedral. The magnetic analysis of Dy2 and Ho2 shows that Dy2 is a single molecular magnet (SMM), with a thermal‐activated zero‐field effective energy barrier (Ueff) of 367.7 K, the largest barrier shown by double phenoxide‐bridged dinuclear dysprosium complexes to date. Ho2is 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 done in order to shed light on the magnetic dynamics of the complexes, and these studies support the experimental magnetic results.