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·Y); Gd (1·Gd); Tb (1·Tb); Dy (1·Dy); Ho (1·Ho); and Er (1·Er)) and [(L)­Ln­(TPPO)­(NO3)] (Ln = Y (2·Y) and Dy (2·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·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, Ueff/kB = 47 K under Hdc = 1 kOe among the complexes presented herein.本研究合成了一系列空气稳定的单核八配位镧系(III)（Ln(III)）配合物，包含两类结构：其一为[(L)­Ln­(TPPO)₃]­OTf，对应Ln分别为钇(Y)（记为1·Y）、钆(Gd)（1·Gd）、铽(Tb)（1·Tb）、镝(Dy)（1·Dy）、钬(Ho)（1·Ho）与铒(Er)（1·Er）；其二为[(L)­Ln­(TPPO)­(NO₃)]，对应Ln为钇(Y)（2·Y）与镝(Dy)（2·Dy）。该系列配合物以刚性N₃O₂-五齿螯合配体作为主配体，并辅以经式辅助配体，其中配体前体H₂L = 2,6-二乙酰吡啶双苯甲酰腙，TPPO为三苯基氧膦（triphenylphosphine oxide），OTf–为三氟甲磺酸根（trifluoromethanesulfonate）。 所有配合物均在有氧条件下合成，并通过光谱学与X射线晶体学技术完成了全面表征。 本研究对1·Ln（Ln = Gd、Tb、Dy、Ho、Er）与2·Dy的多晶固体样品开展了磁性质探究。 结果显示，镝基衍生物均表现出场诱导单分子磁体（single-molecule magnet）行为；其中1·Dy在直流磁场（Hdc）= 1 kOe条件下，展现出本系列所有配合物中最高的磁化反转有效能垒Ueff/kB = 47 K。