Synthesis, Crystal Structures and Photoluminescent Properties of One-Dimensional Europium(III)- and Terbium(III)-Glutarate Coordination Polymers, and Their Applications for the Sensing of Fe(3+) and Nitroaromatics

Two lanthanide–glutarate coordination polymers, viz. : {[Eu(C(5)H(6)O(4))(H(2)O)(4)]Cl}(n), (1) and [Tb(C(5)H(7)O(4))(C(5)H(6)O(4))(H(2)O)(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 EuO(9) 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 TbO(9) 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···O and O–H···Cl hydrogen bonds in 1, and O–H···O hydrogen bonds in 2. Compound 1 exhibits a red emission attributed to the (5)D(0) → (7)F(J) (J = 1–4) transitions of the Eu(III) ion, whereas 2 displays green emission corresponding to the (5)D(4) → (7)F(J) (J = 0–6) transitions of the Tb(III) ion. Both the compounds exhibit high sensitivity and selectivity for Fe(3+) ions due to luminescence quenching compared with other metal ions, which include; Na(+), Mg(2+), Al(3+), Cr(3+), Mn(2+), Fe(2+), Co(2+), Ni(2+), Zn(2+) and Cd(2+). 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.