(Boratabenzene)(cyclooctatetraenyl) lanthanide complexes: a new type of organometallic single-ion magnet

Abstract

A series of new sandwich type lanthanide complexes containing both boratabenzene and cyclooctatetraenyl ligands, [(C₅H₅BR)Ln(COT)] (1Er: R = H, Ln = Er; 2Er: R = Me, Ln = Er; 3Er: R = NEt₂, Ln = Er; 4Dy: R = H, Ln = Dy; 5Dy: R = Me, Ln = Dy; 6Dy: R = NEt₂, Ln = Dy; 7Y: R = NEt₂, Ln = Y), were synthesized. The structures of 1Er–7Y were all characterized by single crystal X-ray diffraction. Dynamic susceptibility experiments showed that the erbium complexes 1Er–3Er exhibited slow magnetic relaxation under zero dc field while the dysprosium complexes 4Dy–6Dy did not. For the erbium complexes, the magnetic properties were influenced by the substituent on the boron atom. 1Er exhibited hysteresis up to 8 K, and 2Er featured the highest energy barrier (300 cm⁻¹) among all the reported erbium single-ion magnets (SIMs). The influence of the boron substituent on the magnetic properties was highlighted by ab initio calculations.