Rigid N(3)O(2)-Pentadentate Ligand-Assisted Octacoordinate Mononuclear Ln(III) Complexes: Syntheses, Characterization, and Slow Magnetization Relaxation.

A series of air-stable mononuclear octacoordinate Ln(III) complexes, [(L)Ln(TPPO)(3)]OTf (Ln = Y (1·Y); Gd (1·Gd); Tb (1·Tb); Dy (1·Dy); Ho (1·Ho); and Er (1·Er)) and [(L)Ln(TPPO)(NO(3))] (Ln = Y (2·Y) and Dy (2·Dy)), are synthesized employing a rigid N(3)O(2)-pentadentate chelating ligand as the basis ligand and meridional ancillary ligands (where H(2)L = 2,6-diacetylpyridine bis-benzoylhydrazone, TPPO = triphenylphosphine oxide, and OTf(-) = trifluoromethanesulfonate). All the complexes are synthesized under aerobic conditions and characterized comprehensively by spectroscopic and X-ray crystallographic techniques. Magnetic property investigation on the polycrystalline solid samples of 1·Ln (Ln = Gd, Tb, Dy, Ho, and Er) and 2·Dy are reported. A field-induced single-molecule magnet behavior was observed for the Dy derivatives. 1·Dy exhibits the highest effective energy barrier of magnetization reversal, U (eff)/k (B) = 47 K under H (dc) = 1 kOe among the complexes presented herein.