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One 2D Gd(III)-based polymer with trans -aconitate ligand was synthesized solvothermally and displays a large cryogenic MCE with the maximum −ΔS m value of 35.89 J kg−1 K−1 at 2 K and Δ H =7 T. • The first Gd(III) polymer based on trans -aconitate ligand was prepared solvothermally. • The polymer owns a 2D layer structure with a metal skeleton of co-edge parallelogram. • The polymer displays a significant MCE of −Δ S m = 35.89 J kg−1 K−1. One two-dimensional Gd(III) coordination polymer based on trans -aconitic acid (H 3 ANA) ligand, [Gd(ANA)(DMF)(H 2 O) 2 ] n (1), was prepared solvothermally and characterized structurally. Single crystal X-ray diffraction analysis reveals that complex 1 crystallizes in monoclinic P 2 1 /c space group and possesses a 2D layer structure containing 3-connected Gd(III) ion and tridentate ANA3− ligand. The 2D structure owns a metal skeleton of co-edge parallelogram with the Gd⋯Gd distances of 8.36 (1) Å × 9.48 (1) Å. Magnetic studies demonstrate that 1 displays weak ferromagnetic interaction between the neighboring Gd(III) ions from the adjacent 2D layers, and has a large cryogenic magnetocaloric effect with the maximum − ΔS m value of 35.89 J kg−1 K−1 at 2 K and Δ H = 7 T. [ABSTRACT FROM AUTHOR]

Two series of lanthanide complexes based on 4-chlorophenylacetic acid (HCPA), dinuclear [Ln 2 (CPA) 6 (DMF) 2 (H 2 O) 2 ] (Ln = Eu (1); Gd (2); Tb (3); Dy (4)) and one-dimensional (1D) linear [Ln 2 (CPA) 6 (H 2 O)] n (Ln = Eu (5); Gd (6); Tb (7); Dy (8)), were prepared, which are sensitive to the pH value. The dinuclear structure can be obtained when the pH value was controlled to be about 4.2, while the 1D structure can be formed when the pH value is ca. 5.1. The structure transformation of the dinuclear to 1D analogue at different pH values indicates that the CPA− ligand has a better affinity to replace the H 2 O/DMF molecule to bridge the neighboring Ln3+ ions to form the 1D structure at a higher pH value (∼5.1). The magnetic studies show that complexes 2 and 6 with isotropic Gd3+ ion display significant cryogenic magnetocaloric effect with a maximum −ΔS m value of 20.27 J kg−1 K−1 at 3 K and 7 T and 22.50 J kg−1 K−1 at 2 K and 7 T, respectively. Furthermore, the solid-state photophysical properties of 1 / 5 and 3 / 7 were studied and respectively exhibit strong characteristic emission peaks of Eu3+ and Tb3+ ions in the visible region, indicating that Eu- and Tb-based luminescences are sensitized effectively by the energy transfe from the ligand to the spin centers. Two series of dinuclear and 1D lanthanide complexes have been successfully prepared with HCPA, and are sensitive to pH value. The Gd-containing complexes display significant MCE, and the Eu- and Tb-based polymers exhibit strong characteristic lanthanide luminescence. Image 1 • Two series of lanthanide complexes were obtained solvothermally. • The dinuclear or 1D complexes are sensitive to the pH value. • The Gd-based complexes display significant MCE. • The Eu- and Tb-based complexes display characteristic Eu3+/Tb3+ luminescence. [ABSTRACT FROM AUTHOR]