Syntheses of three new isostructural lanthanide coordination polymers with tunable emission colours through bimetallic doping, and their luminescence sensing properties

Abstract

Tuning the emissive color changes of lanthanide (Ln) complexes is an important and appealing project for promoting the applications of Ln-complexes. A solvothermal reaction of 4-cyano-3-methylbenzoic acid (HL) and Ln(NO₃)₃·6H₂O affords three isostructural Ln-complexes [Eu(L)₃(H₂O)₂]_n (1-Ln) (Ln = Eu, Gd and Tb) with one-dimensional chain structures. 1-Eu and 1-Tb show bright red and green emissions with absolute quantum yields of 3.06% and 11.96%, respectively, and the energy transfer was analyzed in detail through combined calculations. Interestingly, a series of heterometallic doped 1-Tb_xEu_1−x coordination polymers were also obtained by mixing different ratios of Eu³⁺ and Tb³⁺ ions, which possess continuous luminescent color changes from green to yellow, orange and red. In addition, 1-Eu exhibits high quenching efficiency and low detection limit (∼10⁻⁴ M) for the simultaneous sensing of MnO₄⁻, CrO₄²⁻ and Cr₂O₇²⁻ ions in water.