Synthesis,structural characterization and photophysical properties of highly photoluminescent crystals of Eu(III), Tb(III) and Dy(III) with 2,5-thiophenedicarboxylate

Lanthanide compounds of general formula Ln₂(2,5-tdc)₃(dmf)₂(H₂O)₂]·2dmf·H₂O (Ln = Eu(III) (1), Tb(III) (2), Gd(III) (3) and Dy(III) (4), dmf = N,N′-dimethylformamide and 2,5-tdc^2? = 2,5-thiophedicarboxylate anion) were synthesized and characterized by elemental analysis, X-ray powder diffraction patterns, thermogravimetric analysis and infrared spectroscopy. Phosphorescence data of Gd(III) complex showed that the triplet states (T₁) of 2,5-tdc^2? ligand have higher energy than the main emitting states of Eu(III), Tb(III) and Dy(III), indicating that 2,5-tdc^2? ligand can act as intramolecular energy donor for these metal ions. An energy level diagram was used to establish the most relevant channels involved in the ligand-to-metal energy transfer. The high value of experimental intensity parameter Ω₂ for the Eu(III) complex indicate that the europium ion is in a highly polarizable chemical environment. The emission quantum efficiency (η) of the ⁵D₀ emitting level of Eu(III) was also determined. The complexes act as possible light conversion molecular devices (LCMDs).