Probing the Magnetization Relaxation Dynamics of Four-Coordinate Lanthanide(III) Complexes

The reaction of bulky trimethylsilylanilide (N-TMSA) ligand with various lanthanide salts led us to isolate unusual and unique four-coordinate monomeric Ln­(III) complexes which are challenging to isolate and not surprisingly rare in the literature. The single crystal X-ray diffraction unveils that all the complexes are monomeric and isostructural with the general molecular formula of [Ln­(N-TMSA)3(THF)] where Ln = Dy (1) or Yb (2). Both complexes are found to possess distorted tetrahedral geometry. For all the complexes, detailed dc and ac susceptibility measurements were performed and both 1 and 2 show frequency-dependent out-of-phase susceptibility signals only in the presence of an optimum external magnetic field. The experimental observations are well supported by theoretical calculations and developed magneto-structural correlation using the various model complexes.