Crystal-to-crystal investigations of highly thermally stable three-dimensional coordination polymer based on sodium(I) ions and 4,4’-stilbenedicarboxylic acid

Abstract

The new three-dimensional coordination polymer termed {[Na<sub>2</sub>SDC(H<sub>2</sub>O)]}<sub>n</sub> (SDC<sup>2-</sup>= C<sub>16</sub>H<sub>10</sub>O<sub>4</sub><sup>2-</sup>) has been synthesized using workstation Easymax 102 while controlling the conditions and monitoring in-situ reagents. The metal complex was obtained in the reaction of sodium hydroxide with a suspension of 4,4’-stilbenedicarboxylic acid in aqueous medium. The compound was characterized by elemental analysis, single crystal, and powder X-ray diffraction methods, ATR-FTIR spectroscopy, SEM and optical microscopy, TG-DSC and TG-FTIR thermal analysis in air and nitrogen atmosphere. In the crystal structure of {[Na<sub>2</sub>SDC(H<sub>2</sub>O)]}<sub>n</sub> appears penta- and hexacoordinated sodium atoms joined by octa- and decadentate SDC2- linkers. Aqua ligand acts as bridge between Na1 and Na2 atoms. The as-synthesized sodium complex is thermally stable up to 86<sup>o</sup>C whereas its dehydrated form has extreme stability up to 491<sup>o</sup>C. Removal of water molecule leads to the crystal-to-crystal transformation yielded changes in coordination modes of COO groups. Reversibility of the hydration process in the studied complex was also examined.