Rigid N3O2-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 center dot Y); Gd (1 center dot Gd); Tb (1 center dot Tb); Dy (1 center dot Dy); Ho (1 center dot Ho); and Er (1 center dot Er)) and [(L)Ln(TPPO)(NO3)] (Ln = Y (2 center dot Y) and Dy (2 center dot Dy)), are synthesized employing a rigid N3O2 pentadentate chelating ligand as the basis ligand and meridional ancillary ligands (where H2L = 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 center dot Ln (Ln = Gd, Tb, Dy, Ho, and Er) and 2 center dot Dy are reported. A field-induced single-molecule magnet behavior was observed for the Dy derivatives, 1 center dot 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.