Synthesis, Crystal Structures and Photoluminescent Properties of One-Dimensional Europium(III)- and Terbium(III)-Glutarate Coordination Polymers, and Their Applications for the Sensing of Fe3+ and Nitroaromatics

Two lanthanide-glutarate coordination polymers, viz. : {[Eu(C5H6O4)(H2O)(4)]Cl}(n), (1) and [Tb(C5H7O4)(C5H6O4)(H2O)(2)](n), (2) have been synthesized and characterized by IR spectroscopy, thermogravimetric analysis, and X-ray crystallography. In 1, the Eu(III) ions are coordinated by four O atoms from two bidentate chelating carboxylate groups, one O atom from a bridging carboxylate group and four O atoms from water molecules adopting an EuO9 distorted tri-capped trigonal prismatic coordination geometry. In 2, the Tb(III) ions are coordinated by six O atoms from three bidentate chelating carboxylates, one O atom from a bridging carboxylate and two O atoms from water molecules to generate distorted tri-capped trigonal prismatic TbO9 polyhedron. In both compounds, the metal polyhedra share edges, producing centrosymmetric Ln(2)O(2) diamonds, and are linked into [001] chains by bridging glutarate di-anions. The crystal structures are consolidated by O-H center dot center dot center dot O and O-H center dot center dot center dot Cl hydrogen bonds in 1, and O-H center dot center dot center dot O hydrogen bonds in 2. Compound 1 exhibits a red emission attributed to the D-5(0) -> F-7(J) (J = 1-4) transitions of the Eu(III) ion, whereas 2 displays green emission corresponding to the D-5(4) -> F-7(J) (J = 0-6) transitions of the Tb(III) ion. Both the compounds exhibit high sensitivity and selectivity for Fe3+ ions due to luminescence quenching compared with other metal ions, which include; Na+, Mg2+, Al3+, Cr3+, Mn2+, Fe2+, Co2+, Ni2+, Zn2+ and Cd2+. Compounds 1 and 2 also show high luminescence quenching sensitivity for 4-nitrophenol over the other aromatic and nitroaromatic compounds, namely; bromobenzene, 1,3-dimethylbenzene, nitrobenzene, 4-nitrotolune, 4-nitrophenol, 2,6-dinitrophenol and 2,4,6-trinitrophenol.