Crystallization and single molecule magnetic behavior of quadruple-stranded helicates: tuning the anisotropic axes

It has been successfully proven that the bis-β-diketone ligands with proper lengths and flexibility are essential for the construction of multiple-stranded helicates, where two Dy 3+ centers in subtly different environments allow the tuning of the anisotropic axes. Based on our previous work, we have designed a flexible bis-β-diketone ligand BTT (BTT = 3,3′′-bis(4,4,4-trifluoro-1,3-dioxobutyl)- m -terphenyl), which is successfully utilized to construct quadruple-stranded helicates with the formula of [C 6 H 16 N] 2 [Ln 2 (BTT) 4 ]·2CH 2 Cl 2 ·4CH 3 OH [Ln = Ce ( 1 ), Dy ( 2 )]. Structural analysis indicates that they crystallize in the tetragonal space group P 4/ n , and each Ln 3+ center is chelated by four diketonate moieties from four ligands, giving rise to a dinuclear quadruple-stranded helicate. Magnetic measurements show that 2 displays single molecular magnet behavior under an applied DC field of 2000 Oe. Further investigations indicate that the anisotropic axes of the Dy 3+ centers can be tuned depending on the bis-β-diketonate ligands used to assemble the Dy helicates. Two quadruple-stranded helicates have been prepared, and their unique coordination environment of dinuclear helicates can provide a way to tune the alignment of the anisotropic axes.