Two kinds of 3D coordination frameworks from monometallic to 4d–4f heterometallic: Synthesis, crystal structures, photoluminescence and magnetic properties

• An 3D monometallic complex and the first heterometallic examples based on 2,6-dimethylpyridine-3,5-dicarboxylic acid have been synthesized.
• Two kinds of 3D frameworks feature 5, 6-connected and 3, 4, 5, 6-connected topology, respectively.
• Complexes 1, 3, 5 exhibit characteristic lanthanide-centered luminescence, while compounds 4 and 6 show antiferromagnetic behaviors.

Two kinds of three-dimensional (3D) coordination frameworks from monometallic to heterometallic, including a charming 3D monometallic complex, namely, [Eu2(mpda)3(H2O)4]n (1) and the first series of novel 3D heterometallic 4d–4f coordination frameworks based on 2,6-dimethylpyridine-3,5-dicarboxylic acid, namely, [Ln2Cd2(mpda)2(bdc)2(SO4)2(H2O)6]n [Ln = Sm(2), Eu(3), Gd(4), Tb(5), Dy(6); mpda = 2,6-dimethylpyridine-3,5-dicarboxylic acid; bdc = 1,4-benzenedicarboxylic acid] have been successfully synthesized under hydrothermal conditions and structurally characterized. Crystal 1 is featured by its interesting 3D chain-layer construction which is formed by the alternative arrangement of chains and layers and exhibits 2-nodal 5, 6-connected 3D network with the Schlafli symbol of {33.43.55.64}{36.46.53}. Complexes 2–6 are isostructural and it reveals that these 3D heterometallic compounds are firstly built by H2mpda ligand. What is worth mentioning is that anionic ligand SO42 − plays a crucial function in the construction building. The two-dimensional (2D) lanthanide-transition heterometallic bilayers [Ln2Cd2(mpda)2(bdc)2]n are pillared by SO42 − subunits forming mixed-ligand complexes with a pillared-layer 3D structure. Complexes 2–6 feature 4-nodal 3, 4, 5, 6-connected 3D frameworks with {4.82}{4.84.10}{42.810.102.12}{42.88} topology. All the complexes are characterized by elemental analyses, FT-IR spectroscopy, Powder X-ray diffraction (PXRD) and thermogravimetric analyses (TGA). Furthermore, the luminescence properties of compounds 1, 3, and 5 and the magnetic properties of complexes 4 and 6 were also investigated in detail.

Two kinds of 3D coordination frameworks, containing an interesting 3D monometallic complex and the first series examples of Ln(III)–Cd(II) 4d–4f 3D heterometallic compounds, have been successfully synthesized under hydrothermal conditions based on 2,6-dimethylpyridine-3,5-dicarboxylic acid.Figure optionsDownload as PowerPoint slide