A new photoluminescent terbium(III) coordination network constructed from 1,2,4,5-benzenetetracarboxylic acid: Synthesis, structural characterization and application as a potential marker for gunshot residues

A novel terbium(III) coordination network (CN) of formula [TbHbtec]n 1, constructed from 1,2,4,5-benzenetetracarboxylic acid (H4Btec) and Tb3+ ions, has been obtained under hydrothermal conditions. Single crystal X-ray diffraction and topological studies revealed the crystal structure of CN 1 involves a cubic primitive network with topology pcu-αPo, uninodal and with point symbol (412. 63). In the crystal structure, the ligand is monoprotonated (Hbtec3−) with six Hbtec3− adopting the monodentate, bidentate chelating and bidentate chelating-bridging coordination modes, leading to the formation of a 3-D coordination network. Solid state luminescence spectrum showed the characteristic 5D4 → 7FJ (J = 6–2) transitions of the Tb3+ ion upon excitation in the Hbtec3− singlet levels, revealing that the ligand Hbtec3− is a good sensitizer for the intense green emission of Tb3+ ions. Thermogravimetric analysis (TGA) showed CN 1 has exceptional thermal stability decomposing at temperatures higher than 470 °C. Taking advantage of its excellent thermal and optical properties, the [TbHbtec]n was tested as luminescent marker for gunshot residues, opening the possibility of using this compound in forensic analysis of crime scenes.