Soft magnetic hysteresis in a dysprosium amide–alkene complex up to 100 kelvin

Lanthanides have shown magnetic memory at both the atomic1,2 and molecular3,4 level. The magnetic remanence temperatures of lanthanide single-molecule magnets can surpass d-transition metal examples5,6, and since 2017, energy barriers to magnetic reversal (Ueff) from 1,237(28) cm–1 to 1,631(25) cm–1 and open magnetic hysteresis loops between 40 K and 80 K have typically been achieved with axial dysprosium(III) bis(cyclopentadienyl) complexes7–17. It has been predicted that linear dysprosium(III) compounds could deliver greater mJ (the projection of the total angular momentum, J, on a quantization axis labelled z) state splitting and therefore higher Ueff and hysteresis temperatures18–21, but as lanthanide bonding is predominantly ionic22,23, so far dysprosium bis(amide) complexes have shown highly bent geometries that promote fast magnetic reversal24,25. 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), that shows Ueff = 1,843(11) cm–1 and slow closing of soft magnetic hysteresis loops up to 100 K. Calculations show that the Ueff value for 1-Dy arises from the charge-dense 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 100 times slower than the current best single-molecule magnets above 90 K.