SMM features of a large lanthanide family of butterfly CrIII2LnIII2 pivalate complexes (Ln = Gd, Tb, Dy, Ho, Er, Tm and Yb).

In this work we report the synthesis, structural characterization and magnetic properties of a family of butterfly complexes {Cr 2 Ln 2 } with Ln = Tb (4), Ho (5), Er (6), Tm (7) and Yb (8), extending the family of previously reported isostructural compounds with Gd (1), Dy (2) and Y (3). As in 1 and 2, an anti-ferromagnetic Cr(III)-Ln(III) exchange interaction is found. For oblate ions 4 and 5, SMM behavior with a purely Orbach relaxation mechanism is observed with thermal barriers of 38 cm -1 (4) and 32 cm -1 (5). Complex 4 displays hysteresis opening up to 2.4 K with loss of magnetization at zero field. The prolate complex ions 6 and 7 are field-induced SMM's with dominant Orbach, direct and QTM relaxation mechanisms. Compound 8 did not show SMM properties.