Novel Ba2+ and Pb2+ metal-organic frameworks based on a semi-rigid tetracarboxylic acid: syntheses, structures, topologies and luminescence properties

摘要

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-mu-aqua-diaqua(dimethylformamide)[mu(7)-5,5 '-methylenebis(2,4,6-trimethylbenzene-1,3-dicarboxyl-ato)]dibarium(II)] trihydrate], {[Ba-2(C23H20O8)(C3H7NO)(H2O)(4)]center dot 3H(2)O}(n) or {[Ba-2(BTMIPA)(DMF)(H2O)(4)]center dot 3H(2)O}(n) (1), and poly[[diaqua[mu(6)-5,5 '-methylenebis(2,4,6-trimethylbenzene-1,3-dicarboxylato)]dilead(II)] 2.5-hydrate], {[Pb-2-(C23H20O8)(H2O)(2)]center dot 2.5H(2)O}(n) or {[Pb-2(BTMIPA)(H2O)2]center dot 2.5H(2)O}(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 onedimensional metal chains. The BTMIPA(4-) 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.