Pyrazine-2,3-Carboxylate Based Ag⁺ Homometallic and Ln³⁺–Ag⁺ Heterometallic Coordination Frameworks: Synthesis, Structures, and Magnetic Properties

One Ag+ homometallic complex [Ag4(pzdc)2]·H2O (1), and five Ln–Ag heterometallic complexes, namely, [Gd2Ag6(pzdc)6(H2O)9]·8H2O (2) and [LnAg­(pzdc)2(H2O)2]·2H2O [Ln = Tb (3), Dy (4), Ho (5), Er (6)] based on pyrazine-2,3-dicarboxylate (pzdc2–) have been synthesized under room temperature. Complex 1 exhibits 3D metal–organic framework by Ag2 ions connecting 1D square columns consisting of Ag1 ions and pzdc2– ligands, possessing a unique trinodal net with {42·6}­{43}­{45·64·83·103} topology. Complex 2 displays a 3D heterometal–organic framework with a novel 12-nodal topological net constructed by Gd1 ions linking the adjacent Ag-pzdc2– anion layers. Complexes 3–6 are isostructural 2D Ln–Ag heterometallic coordination frameworks featuring uninodal 4-connected net with {44·62} topology. Magnetic analyses suggest that complexes 4 and 6 exhibit field-dependent slow magnetic relaxation, and complex 6 represents the first slow magnetic relaxation behavior existing in Er3+-based 2D heterometallic coordination framework.