Field-Induced Single-Ion Magnets Based on Enantiopure Chiral β‑Diketonate Ligands

A pair of homochiral β-diketonate
ligands (+)-3-trifluoroacetyl)­camphor (d-Htfc) and
(−)-3-trifluoroacetyl)­camphor (l-Htfc) were
used to construct two enantiomeric pairs of Dy­(III) single-ion magnets
[Dy­(d-tfc)3(bpy)]2 (d-1)/[Dy­(l-tfc)3(bpy)]2 (l-1) (bpy = 2,2′-bipyridine)
and [Dy­(d-tfc)3(phen)]·2H2O (d-2)/[Dy­(l-tfc)3(phen)] (l-2) (phen = 1,10-phenanthroline).
The capping aromatic N,N′-donors
have a dramatic influence on the structural and magnetic characteristics
of the Dy­(III) β-diketonate enantiomeric pairs: the cocrystal
of two homochiral Dy­(III) β-diketonate stereoisomers with the
2,2′-bipyridine ligand was formed, showing field-induced single-ion
magnet behaviors with a two-step relaxation process, while no stereoisomerization
happened for the homochiral Dy­(III) β-diketonate with the 1,10-phenanthroline
coligand, exhibiting a single relaxation process of the magnetization
only. The anisotropy barriers of d-1 (36.5 and 46.1 K) are slightly smaller than those of l-1 (37.0 and 49.3 K), while d-2 has a larger energy barrier (30.5 K) with respect to l-2 (25.1 K).