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

Abstract

A pair of homochiral β-diketonate ligands (+)-3-trifluoroacetyl)­camphor (<i>d</i>-Htfc) and (−)-3-trifluoroacetyl)­camphor (<i>l</i>-Htfc) were used to construct two enantiomeric pairs of Dy­(III) single-ion magnets [Dy­(<i>d</i>-tfc)₃(bpy)]₂ (<i>d</i>-<b>1</b>)/[Dy­(<i>l</i>-tfc)₃(bpy)]₂ (<i>l</i>-<b>1</b>) (bpy = 2,2′-bipyridine) and [Dy­(<i>d</i>-tfc)₃(phen)]·2H₂O (<i>d</i>-<b>2</b>)/[Dy­(<i>l</i>-tfc)₃(phen)] (<i>l</i>-<b>2</b>) (phen = 1,10-phenanthroline). The capping aromatic <i>N</i>,<i>N</i>′-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 <i>d</i>-<b>1</b> (36.5 and 46.1 K) are slightly smaller than those of <i>l</i>-<b>1</b> (37.0 and 49.3 K), while <i>d</i>-<b>2</b> has a larger energy barrier (30.5 K) with respect to <i>l</i>-<b>2</b> (25.1 K)