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, DyN (SiiPr3) [Si (iPr) 2C (CH3) =CHCH3N (SiiPr3) (SiiPr2Et) ]AlOC (CF3) 34 (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.