2D lanthanide coordination polymers constructed from a semi-rigid tricarboxylic acid ligand: crystal structure, luminescence sensing and color tuning

Abstract

Three lanthanide polymers {[Ln(TMCA)(DEF)(H₂O)]·(CH₃CN)}_n (Ln = Eu 1; Tb 2; Gd 3; H₃TMCA = 4′,4′,4′-[(trimethylamino)]-tris[(1,1′-biphenyl)-2-carboxylic acid]) were synthesized under solvothermal conditions. The coordination polymers were characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis and single-crystal X-ray diffraction. Single crystal X-ray diffraction analyses showed that the complexes 1, 2 and 3 are isostructural 2D coordination networks with a point symbol of {4⁴·6²}. Complexes 1 and 2 exhibit red and green emission, assigned to the ⁵D₀ → ⁷F_J (J = 0–4) transitions of the Eu³⁺ ion and ⁵D₄ → ⁷F_J (J = 6–2) transitions of the Tb³⁺ ion, respectively. The luminescence explorations reveal that the Eu-MOF possesses favorable selectivity and sensitivity for testing Fe³⁺ in CH₃OH solutions. Additionally, color tuning was easily achieved by varying the europium : terbium metal ratios in the reaction mixtures.