Toward a Rational Design of 3d-4f Heterometallic Coordination Polymers based on Mixed Valence Copper Centers

In the present work, we report two new Cu-I/Cu-II-Gd-III mixed valence heterometallic coordination polymers (HCP), [Gd(H2O)(4)(CuCuI)-Cu-II(IDC)(2)] (1) and [Gd-2(H2O)(2)(C2O4)(2)Cu-II(IDC)(2)Cu-2(I)(4,4'-bipy)]-4.SH2O (2) obtained under solvothermal synthesis using 1H-imidazole-4,5-dicarboxylic acid (H3IDC) as a principal N,O-bifunctional organic linker. In both compounds, the stabilization of the Cu-I cations is achieved only by the coordination of N-atoms belonging to the organic ligands. While 1 presents a two-dimensional honeycomb network obtained by the coordination of single organic linker (IDC3-), 2 contains three different organic ligands (IDC3-, C2O42-, and 4,4'-bipy), which allow the construction of a three-dimensional network. From a magnetic point of view, 1 and 2 behave as simple paramagnets at high temperature, presenting ferromagnetic interactions below 50 K, and a positive magnetic coupling constant of J = 0.60 cm(-1) and J = 0.22 cm(-1) was obtained for 1 and 2 respectively. To the best our knowledge, 1 and 2 correspond to the second and third reported examples containing a Cu-I/Cu-II mixed valence system assembled with Gd-III cations, thus enriching the chemistry involved in 3d-4f metal-organic materials.