Approaching the 1000 K energy barrier in high coordinate lanthanide single-ion magnets: Increasing U eff in the [Dy(Tp 2-py )F] + moiety with tetrahydrofuran.

Using the existing architecture of [Dy(Tp 2-py )F] + that supports a terminal Dy-F bond, the synthesis and isolation of [Dy(Tp 2-py )F(THF) 2 ](PF 6 ) and its diamagnetic yttrium analogue have been achieved. Alternating current magnetic susceptibility studies show an increased effective energy barrier of U eff = 661(6) cm -1 (951(8) K), the highest yet reported for a high coordinate ( n > 8) lanthanide single-ion magnet.