Soft magnetic hysteresis in a dysprosium amide-alkene complex up to 100 K

Lanthanides have recently shown magnetic memory at both the atomic and molecular level. The temperatures at which single-molecule magnets (SMMs) show magnetic hysteresis only increased from 4 K to 14 K in nearly 25 years since the discovery of the first SMM in 1993. However, since 2017 energy barriers to magnetic reversal (Ueff) from 1237(28)-1631(25) cm–1 and open magnetic hysteresis loops between 40-80 K have often been delivered by molecules featuring rigid aromatic ligands in axial dysprosium cyclopentadienyl complexes and their derivatives. Here we report a dysprosium bis(amide)-alkene complex, [Dy{N(SiiPr3)[Si(iPr)2C(CH3)=CHCH3]}{N(SiiPr3)(SiiPr2Et)}][Al{OC(CF3)3}4] (1-Dy), which shows Ueff = 1843(11) cm–1 and slow closing of magnetic hysteresis loops up to 100 K. Calculations show that the record Ueff value of 1-Dy arises from the charge-dense bis(silyl)amide ligands, with a pendant alkene taking a structural role to enforce a large N–Dy–N angle while imposing only a weak equatorial interaction. This leads to molecular spin dynamics up to one hundred times slower than the current best SMMs above 100 K.