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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