Significant increase of the barrier energy for magnetization reversal of a single-4f-ionic single-molecule magnet by a longitudinal contraction of the coordination space.

Two-electron oxidation of [{Pc(OEt)8}2TbIII]- [Pc(OEt)8=dianion of 2,3,9,10,16,17,23,24-octaethoxyphthalocyanine], which leads to a longitudinal contraction of the coordination space of the single-4f-ionic single-molecule magnet (SMM), resulted in a significant increase of the magnetization-reversal barrier energy and a remarkable upward temperature shift of chi'' peaks and chi'T drops. This is the first evidence that the dynamic magnetism of 4f SMMs can be controlled by a redox reaction on the ligand side without introducing any additional magnetic site or spin system.