Substitution Effects Regulate the Formation of Butterfly-Shaped Tetranuclear Dy(III) Cluster and Dy-Based Hydrogen-Bonded Helix Frameworks: Structure and Magnetic Properties

The generation of two types of complexes with different topological connections and completely different structural types merely via the substitution effect is extremely rare, especially for −CH3 and −C2H5 substituents with similar physical and chemical properties. Herein, we used 3-methoxysalicylaldehyde, 1,2-cyclohexanediamine, and Dy­(NO3)3·6H2O to react under solvothermal conditions (CH3OH:CH3CN = 1:1) at 80 °C to obtain the butterfly-shaped tetranuclear DyIII cluster [Dy4(L 1 )4(μ3-O)2(NO3)2] (Dy 4 , H2 L 1 = 6,6′-((1E,1′E)-(cyclohexane-1,3-diylbis­(azanylylidene))­bis­(methanylylidene))­bis­(2-methoxyphenol)). The ligand H2 L 1 was obtained by the Schiff base in situ reaction of 3-methoxysalicylaldehyde and 1,2-cyclohexanediamine. In the Dy 4 structure, (L 1 )2– has two different coordination modes: μ2-η1:η2:η1:η1 and μ4-η1:η2:η1:η1:η2:η1. The four DyIII ions are in two coordination environments: N2O6 (Dy1) and O9 (Dy2). The magnetic testing of cluster Dy 4 without the addition of an external field revealed that it exhibited a clear frequency-dependent behavior. We changed 3-methoxysalicylaldehyde to 3-ethoxysalicylaldehyde and obtained one case of a hydrogen-bonded helix framework, [DyL 2 (NO3)3] n ·2CH3CN (Dy-HHFs, H2 L 2 = 6,6′-((1E,1′E)-(cyclohexane-1,3-diylbis­(azanylylidene))­bis­(methanylylidene))­bis­(2-ethoxyphenol)), under the same reaction conditions. The ligand H2 L 2 was formed by the Schiff base in situ reaction of 3-ethoxysalicylaldehyde and 1,2-cyclohexanediamine. All DyIII ions in the Dy-HHFs structure are in the same coordination environment (O9). The twisted S-shaped (L 2 )2– ligand is linked by a Dy­(III) ion to form a spiral chain. The spiral chain is one of the independent units that is interconnected to form Dy-HHFs through three strong hydrogen-bonding interactions. Magnetic studies show that Dy-HHFs exhibits single-ion-magnet behavior (U eff = 68.59 K and τ0 = 1.10 × 10–7 s, 0 Oe DC field; U eff = 131.5 K and τ0 = 1.22 × 10–7 s, 800 Oe DC field). Ab initio calculations were performed to interpret the dynamic magnetic performance of Dy-HHFs, and a satisfactory consistency between theory and experiment exists.