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.