New members of radical bridged Ln2 metallocene single-molecule magnets based on the unsubstituted 1,2,4,5-tetrazine ligand†
Magnetic coupling plays a critical role in the overall magnetic behaviour of a single-molecule magnet (SMM). Through a careful design strategy that employs the highly delocalized 1,2,4,5-tetrazinyl (tz) radical anion with lanthanide metallocenes, a new family of dinuclear complexes was isolated; [(Cp*2LnIII)2(tz˙−)(THF)2](BPh4), (Ln = Gd (1), Tb (2), Dy (3); THF = tetrahydrofuran; Cp* = pentamethylcyclopentadienyl). The strong magnetic exchange coupling of JGd–rad = −7.2 cm−1 observed in 1, was probed through SQUID magnetometry as well as computational studies. This, combined with the highly anisotropic TbIII and DyIII ions in 2 and 3, respectively, leads to zero-field SMM behaviour and slow relaxation of the magnetization through thermally activated processes. These dinuclear complexes serve as ideal models for understanding the magnetic interactions between 4f elements.