Field-induced slow magnetic relaxation in chiral seven-coordinated mononuclear lanthanide complexes

Four couples of enantiomerically pure chiral seven-coordinated mononuclear lanthanide complexes, [(L-OEt)Dy((R,R)-Salphen)](2)center dot 3H(2)O (1, L-OEt = [(Cp)Co(P(O)(OEt)(2))(3)], Cp = cyclopentadiene, Salphen = N,N'-1,2-diphenylethylenebis(salicylideneiminato) dianion), [(L-OEt)Dy((S,S)-Salphen)](2)center dot 3H(2)O (2), [(L-OEt)Dy((R,R)-5-Cl-Salcy)]center dot CH3OH center dot 1/8H(2)O (3, Salcy = N,N'-(1,2-cyclohexanediylethylene)bis(salicylideneiminato) dianion), [(L-OEt)Dy((S,S)-5-Cl-Salcy)]center dot CH3OH center dot 1/8H(2)O (4), [(L-OEt)Tb((R,R)-5-Cl-Salcy)]center dot CH3OH center dot 1/8H(2)O (5), [(L-OEt)Tb((S,S)-5-Cl-Salcy)]center dot CH3OH center dot 1/8H(2)O (6), [(L-OEt)Ho((R,R)-5-Cl-Salcy)]center dot CH3OH center dot 1/8H(2)O (7) and [(L-OEt)Ho((S,S)-5-Cl-Salcy)]center dot CH3OH center dot 1/8H(2)O (8), have been successfully synthesized by using tetradentate chiral salen-type ligands and the Klaui's tripodal ligand of LOEt. Structural analyses reveal that all compounds have a typical double-decker sandwich structure, and the Ln(III) ions exhibit a rare seven-coordinated mode, situating in a distorted monocapped triangular prism polyhedron. Circular dichroism (CD) spectra confirm the enantiomeric nature of the optically active complexes and demonstrate that the chirality is successfully transferred from the ligand to the coordination environment of the Ln(III) ions. Field-induced slow relaxation of the magnetization is observed for complexes 1-4, suggesting that they can be rare chiral single-ion magnets (SIMs) based on the seven-coordinated lanthanide ions.