SMM Behaviour of the Butterfly {(Cr2Dy2III)-Dy-III} Pivalate Complex and Magneto-structurally Correlated Relaxation Thermal Barrier

We are reporting the synthesis, single-crystal X-ray structure characterization, and magnetic property investigations of the pivalate butterfly {Cr(2)(III)Ln(2)(III)} complexes with Ln= Gd and Dy and the isostructural Y(III) sample. We found an anti-ferromagnetic Cr(III)-Ln(III) exchange interaction, which, as previously observed in related Cr(III)/Ln(III) systems, plays a key role in suppressing quantum tunnelling of magnetization and enhances the SMM performance in the Dy(III) complex. In fact, a pure Orbach relaxation mechanism, with absence of QT regime, is observed with a thermal barrier of 50 cm(-1), leading to magnetization hysteresis opening, measured with a commercial magnetometer, up to 3.6 K with a coercive field of 2.9 T. Analysis of SMM behaviour in literature-known butterfly {(Cr2Dy2III)-Dy-III} complexes, reveals the existence of a magneto-structural correlation between U-eff, the thermal barrier size, and the mean Cr-Dy bond distances. Moreover, a clear correlation is found for the thermal barrier magnitude and the maximum temperature hysteresis opening and coercive field.