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

•Reaction between 2,5-tdc ligand and lanthanide ions afforded luminescent crystals.•PXRD patterns reveals that Dy(III) compound exhibits a different crystal packing.•2,5-tdc2− ligand triplet states energy is above lanthanide ions energy levels.•Judd–Ofelt experimental intensity parameters for Eu(III) complex were calculated.•Optical properties showed that these complexes are potential emitters in photonics.

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-tdc2− = 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-tdc2− ligand have higher energy than the main emitting states of Eu(III), Tb(III) and Dy(III), indicating that 2,5-tdc2− 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).

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