Protonation-Induced Slow Magnetic Relaxation of Mononuclear Dy(III) Complexes

The development of single-molecule magnets that respond to small modulations of an external field is of interest from two perspectives: understanding the magnetic relaxation mechanism and its application in molecular-based nanodevices. This study discusses the correlation between the coordination structure and magnetic properties, in particular the onset of slow magnetic relaxation, in nona-coordinated Dy(III) complexes with D3 point group local symmetry [C(NH2)3]3[Dy(pydc)3] (1) and protonated congeners [Ln(Hpydc)3]·1.5H2O (Ln = Dy (2) or Dy0.07Y0.93 (3), H2pydc denotes 2,6-pyridinedicarboxylic acid). Although the coordination geometry of Dy(III) was maintained with or without protonation, 1 showed no slow magnetic relaxation, whereas protonated 2 and 3 exhibited slow magnetic relaxation under the application of an external direct current (DC) field. The drastic change in the magnetic relaxation induced by protonation is discussed in detail based on experiments and theoretical ab initio calculations.