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

Abstract

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.