Four one-dimensional lanthanide–phenylacetate polymers exhibiting luminescence and magnetic cooling/spin-glass behavior

Four isostructural lanthanide coordination polymers with a phenylacetate (PAA^-) ligand, [Ln(PAA)₃(H₂O)]_n (Ln = Eu (1); Gd (2); Tb (3); Dy (4)), were synthesized under hydrothermal conditions. Complexes 1-4 display a one-dimensional (1D) wave chain structure bridged by the carboxylate of the PAA^- ligand, which was generated via the in situ decarboxylation of phenylmalonic acid. Magnetic studies suggest the presence of ferromagnetic LnLn coupling in the 1D chain of 1-4. Meanwhile, 2 has a significant cryogenic magnetocaloric effect with the maximum -ΔS_m of 26.73 at 3 K and 7 T, and 3 and 4 show interesting spin-glass behavior, which is rarely reported for Ln-containing complexes. Additionally, the solid-state photophysical properties of 1 and 3 display strong characteristic Eu³⁺ and Tb³⁺ photoluminescence emission in the visible region, indicating that Eu- and Tb-based luminescence are sensitized by the effective energy transfer from the ligand to the metal centers.