Synthesis, structure and properties of a new Sm(III) rare-earth metal coordination complex with 2,5-dihydroxy-terephthalic acid ligand

A new Sm(III) coordination complex, [Sm(DHTA)4(H2O)3]n, was synthesized with 2,5-dihydroxyterephthalic acid (H2DHTA) as ligand. The crystal structure and properties were characterized by single crystal X-ray diffraction, IR, elemental analysis and TGA analysis. The single-crystal X-ray diffraction analysis showed that Sm(III) ion is nine-coordinate with six oxygen atoms of four DHTA ligands and three oxygen atoms of three H2O molecules, forming a tri-capped trigonal-prism configuration. The adjacent units of the complex are extended into a 3 D supramolecular network. In the IR spectrum of the complex, there are asymmetric and symmetric stretching vibrations of C = O of the carboxyl group. The complex has two weight loss steps in the TG plot. The complex’s UV-Vis absorptions at 400 and 261 nm are attributed to the DHTA. Furthermore, there is a fluorescent maximum emission at 476 nm, which is derived from the ligand. The fluorescence is attributed to the ligand-ligand charge transfer of the complex.