Design principle of half-sandwich type erbium single-ion magnets through crystal field engineering: a combined magnetic and electronic structure study.

To conclude the design principle for high-performance erbium-based single-ion magnets (SIMs), two half-sandwich type erbium complexes 1Er [(LOMe)Er(COT)] (LOMe = [(η5-C5H5)Co{P([double bond, length as m-dash]O)(OMe)2}3], COT = cyclooctatetraenyl) and 2Er [(THF)2(OAr)Er(COT)] (Ar = 2,6-Dipp2C6H3, Dipp = 2,6-diisopropylphenyl) were synthesized, and structurally and magnetically characterized. Both of them exhibited SIM behavior. Their magnetic relaxation behaviours were further elucidated by ab initio calculations and near-IR emission spectroscopy. The results demonstrated that an axial ligand with a weaker electron-donating effect was preferential to construct high blocking barrier erbium-based SIMs.