Slow magnetic relaxation in dinuclear dysprosium and holmium phenoxide bridged complexes: A Dy2single molecule magnet with a high energy barrier

Abstract

Slow magnetic relaxation in dinuclear dysprosium and holmium phenoxo bridged complexes: a Dy2 single molecule magnet with a high energy barrier Matilde Fondo,a,* Julio Corredoira-Vázquez,a Ana M. García-Deibe,a Jesús Sanmartín-Matalobos,a Silvia Gómez-Coca,b Eliseo Ruizb and Enrique Colacioc Dinuclear [M(H3L1,2,4)]2 (M = Dy, Dy2; M = Ho, Ho2) complexes were isolated and recrystallised in pyridine. The crystal structures of Dy2·2THF and the pyridine adducts Dy2·2Py and Ho2·2Py show that the complexes are dinuclear, with unsupported double phenoxo 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 unsupported phenoxo-bridged dinuclear dysprosium complexes. Ho2 is one of the scarce dinuclear complexes showing slow relaxation of the magnetisation, although it does not even show field-induced SMM behaviour. Ab initio calculations were done in order to shed light on the magnetic anisotropy of the complexes and the magnetic relaxation pathways, which support the experimental magnetic results.