Multidentate carboxylate ligands have been widely used in the construction of metal-organic frameworks (MOFs) owing to the rich variety of their coordination modes, which can lead to crystalline products with interesting structures and properties. Two new main-group MOFs, namely, poly[[di-μ-aqua-diaqua(dimethylformamide)[μ7-5,5'-methylenebis(2,4,6-trimethylbenzene-1,3-dicarboxylato)]dibarium(II)] trihydrate], {[Ba2(C23H20O8)(C3H7NO)(H2O)4]·3H2O}n or {[Ba2(BTMIPA)(DMF)(H2O)4]·3H2O}n (1), and poly[[diaqua[μ6-5,5'-methylenebis(2,4,6-trimethylbenzene-1,3-dicarboxylato)]dilead(II)] 2.5-hydrate], {[Pb2(C23H20O8)(H2O)2]·2.5H2O}n or {[Pb2(BTMIPA)(H2O)2]·2.5H2O}n (2), were prepared by the self-assembly of metal salts with the semi-rigid tetracarboxylic acid ligand 5,5'-methylenebis(2,4,6-trimethylisophthalic acid) (H4BTMIPA). Both structures were characterized by elemental analysis (EA), single-crystal X-ray diffraction, powder X-ray diffraction (PXRD), IR spectroscopy and thermogravimetric analysis (TGA). Complex 1 reveals a three-dimensional (3D) flu network formed via bridging tetranuclear secondary building units (SBUs) and complex 2 displays a 3D framework with an sqp topology based on one-dimensional metal chains. The BTMIPA4- ligands adopt a rare coordination mode in 2, although the ligands in both 1 and 2 are X-shaped. The luminescence properties of both complexes were investigated in the solid state.
Keywords: MOF; crystal structure; fluorescence properties; metal-organic framework; semi-rigid tetracarboxylic acid; topological analysis.