A stable dysprosium(iii) complex with a terminal fluoride ligand showing high resolution luminescence and slow magnetic relaxation.

An air-stable dysprosium(iii) complex, [C(NH)][DyF(piv)](piv) (piv = pivalate), with a terminal fluoride ligand protected by forming extensive hydrogen bonds with peripheral guanidiniums has been isolated. Though the magnetic data failed to determine the energy barrier for the magnetic reversal (U) accurately, the fine emission spectrum of the F→H transition at 4.2 K and ab initio calculations reveal that the U is about 376(20) K, which is among the highest for high-coordinate (coordination numbers ≥ 9) lanthanide mononuclear magnets.