Heterometallic coordination polymers based on Cu^II/Ln^III cations. Solid-state and magnetic characterization

Novel heterometallic three-dimensional coordination polymers {[Cu^II₂Ln^IIICl₂(HIA)₄(NO₃)(DMF)₂]∙(2DMF)∙(H₂O)}_n based on Ce (1), Eu (2) or Gd (3) and imidazole-4-acrylic acid (H₂IA), were successfully synthesized using the sonochemical method. All attempts to obtain the compound using other synthetic methods were unsuccessful. The heterometallic polymers are isostructural, crystallizing in the chiral P3₂21 trigonal space group. The crystal structures correspond to an intricated 3D framework where the Cu(HIA)₂ fragments generate two interpenetrated copper (II) networks, [Cu(HIA)₂]_n. The Ln^III cations that interact with these Cu^II-networks through the carboxylate group belonging to the organic ligand confer a higher complexity to the 3D network. Additionally, the coordination environment around the copper (II) cations is responsible for the chirality of the structures, making these even more exciting. The three-dimensional polymers were also characterized from a magnetic point of view, obtaining for (1) and (2) antiferromagnetic interactions, while for (3) a ferromagnetic interaction was observed. Furthermore, to the best of our knowledge, these coordination polymers are the first heterometallic compounds based on 3d/4f cations, assembled by the ligand imidazole-4-acrylate (HIA⁻).