Synthesis, crystal structures and magnetic properties of two heterometallic {Ln8Cr4} (Ln = Gd3+ and Tb3+) complexes with one-dimensional wave chain structure

Abstract

Two isomorphic heterometallic 3d–4f cluster-based materials, formulated [Gd₈Cr₄(IN)₁₈(μ₃-O)₂(μ₃-OH)₆(μ₄-O)₄(H₂O)₁₀]·13H₂O (1) and [Tb₈Cr₄(IN)₁₈(μ₃-O)₂(μ₃-OH)₆(μ₄-O)₄(H₂O)₁₀]·13H₂O (2) (abbreviation: {Ln₈Cr₄}: Ln = Gd³⁺ (1); Tb³⁺ (2); HIN = isonicotinic acid), were achieved by hydro-/solvothermal method through using the ligand HIN. X-ray diffraction analysis illustrates eight lanthanide ions (Ln = Gd³⁺, Tb³⁺) and four transition-metal ions (Cr³⁺) of {Ln₈Cr₄} were constructed from two classical “drum-like” {Ln₄Cr₂} structures associated by organic ligands HIN, displaying a one-dimensional wave chain structure, which is rare. The magnetic properties of {Gd₈Cr₄} were inspected and showed the existence of antiferromagnetic coupling interactions between contiguous metal ions. On top of this, the magnetic entropy change of ΔS_m can attain 23.40 J kg⁻¹ K⁻¹ (44.90 mJ cm⁻³ K⁻¹) at about 3 K and ΔH = 7 T. Besides, fluorescence measurements of {Tb₈Cr₄} display typical characteristic Tb-based luminescence.