Spin dynamics phenomena of a cerium(III) double-decker complex induced by intramolecular electron transfer

Switchable spin dynamic properties in single-molecule magnets (SMMs) via an applied stimulus have applications in single-molecule devices. Many SMMs containing heavy lanthanoid ions with strong uniaxial magnetic anisotropy have been reported to exhibit SMM characteristics in the absence of an external magnetic field. On the other hand, SMMs containing light lanthanoid cerium(III) (Ce³⁺) ions exhibit field-induced slow magnetic relaxation. We investigated the chemical conversion of a diamagnetic Ce⁴⁺ ion (4f⁰) to a paramagnetic Ce³⁺ ion (4f¹) in Ce-phthalocyaninato double-decker complexes (TBA⁺[Ce(obPc)₂]^- (1) and TBA⁺[Ce(Pc)₂]^- (2)) which exhibit field-induced SMM behaviour due to a 4f¹ system. The phthalocyaninato ligands with electron-donating substituents (obPc^2- = 2,3,9,10,16,17,23,24-octabutoxyphthalocyaninato) in 1 have a significant effect on the valence state of the Ce ion, which is reflected in its magnetic properties due to the mixed valence state of the Ce ion. Given that Ce double-decker complexes with π-conjugated ligands undergo intramolecular electron transfer (IET) to the Ce ion mixed valence state, characterised by a mixture of 4f⁰ and 4f¹ configurations, we examined the dynamic disorder inherent in IET influencing magnetic relaxation.