Understanding a pentagonal-bipyramidal holmium(iii) complex with a record energy barrier for magnetisation reversal.

We report herein three pentagonal-bipyramidal holmium(iii) complexes sharing the formula [Ho(L)2(py)5][BPh4], where L is the alkoxide ligand. For L = (OSi(CH3)3)-, a record energy barrier for magnetization reversal (Ueff = 715(6) K) was revealed, which is due to the pure state transition of mJ = |±8 → mJ = |±7 → mJ = |±6.