Tuning symmetry and magnetic blocking of an exchange-coupled lanthanide ion in isomeric, tetrametallic complexes: [LnCl6(TiCp2)3]

The synthesis and magnetic properties of two pairs of isomeric, exchange-coupled complexes, [LnCl(6)(TiCp2)(3)] (Ln = Gd, Tb), are reported. In each isomeric pair, the central lanthanide ion adopts either a pseudo-octahedral (O-Ln) or trigonal prismatic geometry (TP-Ln) yielding complexes with C-1 or C-3h molecular symmetry, respectively. Ferromagnetic exchange coupling is observed in TP-Ln as indicated by the increases in ?T-m below 30 K. For TP-Gd, a fit to the susceptibility reveals ferromagnetic coupling between the Gd3+ ion and the Ti3+ ions (J = 2.90(1) cm(-1)). In contrast to O-Tb, which shows no single-molecule magnetic behavior, the TP-Tb complex presents slow magnetic relaxation with a 100s-blocking temperature of 2.3 K and remanent magnetization at zero field up to 3 K. The calculated electronic structures of both compounds imply that trigonal prismatic geometry of TP-Tb is critical to the observed magnetic behavior.

Automated summary

The synthesis and magnetic properties of two pairs of isomeric, exchange-coupled complexes, [LnCl(6)(TiCp2)(3)] (Ln = Gd, Tb), are studied. The complexes exhibit either pseudo-octahedral or trigonal prismatic geometries, resulting in different magnetic behaviors. Ferromagnetic exchange coupling is observed in the trigonal prismatic complexes, while slow magnetic relaxation is observed in the TP-Tb complex. The electronic structures suggest that the trigonal prismatic geometry is critical for the observed magnetic behavior.