Four unprecedented cobalt(II) and cadmium(II) metal-organic frameworks based on a rigid tricarboxylate ligand: Synthesis, crystal structures, magnetic and fluorescence properties

A Co(II) MOF {[Co3(L)2(H2O)4](DMF)2}n (1) and three Cd(II) MOFs [Cd3(L)2(H2O)7]n (2), [Cd3(L)2(H2O)11]n (3) and [Cd3(L)2(DMF)2(H2O)]n (4) are synthesized based on the promising multifunctional tricarboxylate ligand 6-(3, 5-dicarboxyl phenyl) nicotinic acid (H3L). 1 exhibits a 3D framework with 1D channels which contains opposite-handedness helical chains based on the trinuclear Co(II) clusters. 2-4 are obtained depend on different reaction conditions. 2 displays a 3D framework, which is composed of two kinds of 2D layers linked with each other. 3 shows a rare tongue-and-groove-type bilayer structure. And 4 is an interesting 3D framework containing infinite 1D inorganic CdOCd chains. In these MOFs, the H3L ligand shows the versatile coordination modes and strong coordination ability. Furthermore, the magnetic and solid-state luminescent properties of the MOFs have been investigated.