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.