Preparation and properties of a series of discrete zinc-rare earth heterometallic complexes based on 2,4-dichlorobenzoate and 2,2′-bipyridine

Abstract

By using 2,4-dichlorobenzoic acid (2,4-HDCB) and 2,2′-bipyridine (2,2′-bpy) as mixed ligands, a series of Zn(II)-Ln(III) heterometallic complexes were successfully prepared by solvothermal method, namely [Ln₂Zn₂(2,4-DCB)₁₀(2,2′-bpy)₂] [Ln = Nd (1), Sm (2), Eu (3), Gd (4), Tb (5), Dy (6), Er (7) and Yb (8)]. Complexes 1–8 were characterized by single crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD), elemental analysis (EA), Fourier transform infrared (FT-IR) spectroscopy as well as thermogravimetric analysis (TGA) and differential thermoanalysis (DTA). These eight complexes are isomorphic. They possess discrete linear tetranuclear cluster structures formed by the 2,4-DCB anions bridging the Zn(II) and Ln(III) ions. The adjacent tetranuclear clusters can be connected through the π–π interactions into a two-dimensional (2D) supramolecular layer. The photoluminescent properties of 2, 3, 5 and 6 as well as the magnetic properties of 1 and 4–8 were investigated in detail. The characteristic luminescences of Ln(III) for 2, 3, 5 and 6 as well as the ferromagnetic couplings between the Ln(III) ions for 4–7 were observed. Complex 6 exhibits a slow magnetic relaxation behavior.