Syntheses, structures and magnetic properties of three dinuclear, one-dimensional and two-dimensional dysprosium(iii) complexes based on naphthalene diimide salicylic acid†

Regulation of the complex structure is greatly significant for the preparation of single-molecule magnets (SMMs). In this work, a multidentate ligand of N,N′-bis(3-carboxy-4-hydroxyphenyl)-1,4,5,8-naphthalenetetradicarboximide (H₄NDISA) has been synthesized and reacted with dysprosium(III) salt. By controlling the ratio of metal ions to the ligand and reaction temperature, three new dysprosium(III) complexes are obtained, namely, [Dy₂(H₂NDISA)₃(DMF)₃(H₂O)₁₀]·1.4DMF·2.6H₂O (1), {[Dy(H₂NDISA)_1.5(DMF)(H₂O)₄]·3DMF·4H₂O}_n (2), and {[Dy(HNDISA)(H₂O)₂]·4H₂O}_n (3). Their structures are determined by single crystal X-ray diffraction. Crystallographic data demonstrate that complex 1 is a dinuclear dysprosium(III) complex linked by the bidentate ligand of H₄NDISA. The intramolecular Dy(III)⋯Dy(III) distance is 23.0861(7) Å. In complex 2, the carboxyl group in one of the ligands adopts a μ-η₂:η₁ bridging mode to connect two Dy(III) ions, resulting in a Dy(III)⋯Dy(III) distance of 5.2611(5) Å. The other ligand adopts a tetradentate coordination mode to bridge two Dy(III) ions, forming an infinite one-dimensional chain structure along the c axis. Complex 3 displays a two-dimensional network structure. One carboxyl group in the ligand adopts a μ-η₁:η₁ bridging mode growing along the c axis. Another carboxyl group in the ligand adopts a μ-η₂:η₁ bridging mode. The shortest distance of Dy(III)⋯Dy(III) is 4.6138(5) Å. DC and alternating current (AC) magnetic susceptibilities of complexes 1–3 were measured. AC magnetic susceptibility measurements show that complexes 1–3 exhibit frequency-dependent ac susceptibilities.