Unveiling Single-Ion Magnetism in Lanthanide-Coumarin Carboxylate Coordination Polymers

Abstract

Three new coordination polymers, [Ln(3-CCA)₃(H₂O)₂·2H₂O]ₙ (Ln = Gd (1), Tb (2), Dy (3)), were synthesized through the reaction between the above-mentioned lanthanide ions and the coumarin-3-carboxylic acid (3-CCA). Single-crystal and powder X-ray diffraction analyses revealed that complex 1 exhibits a nona-coordination, whereas complexes 2 and 3 adopt an octa-coordinated geometry. The chemical composition of the complexes was confirmed by FTIR and CHN analyses, while their phase purity was verified by powder X-ray diffraction. DC magnetic measurements revealed the presence of weak ferromagnetic interactions between the Ln ions in 1. Moreover, the magnetocaloric properties of this compound were investigated, and its performance was evaluated using the Temperature-Averaged Entropy Change (TEC) parameter. Additionally, AC magnetic susceptibility measurements revealed field-induced single-ion magnet (SIM) behavior at low temperatures for complexes 2 and 3.