Alkali and alkaline earth coordination polymers constructed from benzene-1,2,4,5-tetracarboxylic acid and flexible dicarboxylate acid ligands: syntheses, structures and spectroscopic and thermal properties.

Two new metal coordination complexes, namely, poly[aqua(μ-benzene-1,2,4,5-tetracarboxylic acid-κO:O,O:O:O:O,O:O)(μ-but-2-enedioato-κO:O)potassium(I)], [K(CHO)(CHO)(HO)] or [K(fum)(Hbtec)(HO)], (1), and poly[aqua(μ-2,5-dicarboxybenzene-1,4-dicarboxylato-κO:O,O:O,O:O:O:O,O:O,O:O)(μ-ethanedioato-κO,O:O,O)strontium(II)], [Sr(CO)(CHO)(HO)] or [Sr(ox)(Hbtec)(HO)], (2) (Hbtec = benzene-1,2,4,5-tetracarboxylic acid, Hbtec = 2,5-dicarboxybenzene-1,4-dicarboxylate, fum = fumarate and ox = oxalate), have been obtained under hydrothermal conditions by reacting the different alkali and alkaline earth metal salts with Hbtec, fumaric acid (Hfum) and oxalic acid (Hox). Complexes (1) and (2) were structurally characterized by single-crystal X-ray diffraction, IR and UV-Vis spectroscopy, powder X-ray diffraction (PXRD) and thermogravimetic analysis-differential scanning calorimetry (TGA-DSC). Complex (1) displays a two-dimensional (2D) layer with the K ion in a distorted pentagonal bipyramidal geometry and exhibits a uninodal 6-connected hxl/Shubnikov plane net (3,6) with {3.4.5} topology. Complex (2) displays a three-dimensional (3D) network structure, in which the Sr ion is in a distorted monocapped square antiprism geometry. The framework possess a binodal (5,8)-connected net with the Schläfli symbol {3.4.5.6.7}{3.4.5}. The 3D Hirshfeld surfaces and 2D fingerprint plots show that the main interactions are the O...H/H...O intermolecular interactions. Moreover, the thermal decompositions of (1) and (2) in the temperature range 303-1273 K revealed that they both decompose in three steps and transform to the corresponding metal oxide.