Molecular Magnets Based on Homometallic Hexanuclear Lanthanide(III) Complexes

The reaction of lanthanide­(III) chloride salts (Gd­(III), Dy­(III), Tb­(III), and Ho­(III)) with the hetero donor chelating ligand <i>N</i>′-(2-hydroxy-3-methoxybenzylidene)-6-(hydroxymethyl)­picolinohydrazide (LH₃) in the presence of triethylamine afforded the hexanuclear Ln­(III) complexes [{Ln₆(L)₂(LH)₂}­(μ₃-OH)₄]­[MeOH]_<i>p</i>[H₂O]_<i>q</i>[Cl]₄·<i>x</i>H₂O·<i>y</i>CH₃OH (<b>1</b>, Ln = Gd­(III), <i>p</i> = 4, <i>q</i> = 4, <i>x</i> = 8, <i>y</i> = 2; <b>2</b>, Ln = Dy­(III), <i>p</i> = 2, <i>q</i> = 6, <i>x</i> = 8, <i>y</i> = 4; <b>3</b>, Ln = Tb­(III), <i>p</i> = 2, <i>q</i> = 6, <i>x</i> = 10, <i>y</i> = 4; <b>4</b>, Ln = Ho­(III), <i>p</i> = 2, <i>q</i> = 6, <i>x</i> = 10, <i>y</i> = 2). X-ray diffraction studies revealed that these compounds possess a hexanuclear [Ln₆(OH)₄]¹⁴⁺ core consisting of four fused [Ln₃(OH)]⁸⁺ subunits. Both static (dc) and dynamic (ac) magnetic properties of <b>1</b>–<b>4</b> have been studied. Single-molecule magnetic behavior has been observed in compound <b>2</b> with an effective energy barrier and relaxation time pre-exponential parameters of Δ/<i>k</i>_B = 46.2 K and τ₀ = 2.85 × 10^–7 s, respectively