abstract
Luminescent trivalent lanthanide (Ln(3+)) complexes are compounds of technological interest due to their unique photophysical properties, particularly anionic tetrakis complexes, given their higher stability and emission quantum yields. However, structural studies on the cation-anion interaction in these complexes and the relation of such to luminescence are still lacking. Herein, the cation-anion interactions in two luminescent anionic tetrakis(2-thenoyltrifluoroacetonato)europate(III) complexes with alkylimidazolium cations, specifically 1-ethyl-3-methylimidazolium and 1-butyl-3-methylimidazolium are investigated. The Eu3+ complexes were synthesized and characterized by elemental analysis, mass spectrometry, and single-crystal X-ray crystallography, and their luminescence spectra were recorded at 77 K. Quantum chemical calculations were also performed. X-ray crystallography revealed hydrogen bonds between the enolate ligands and imidazolium ring hydrogens. The 1-butyl-3-methylimidazolium complex had two crystallographic Eu3+ sites, also confirmed by luminescence spectroscopy. The 1-ethyl-3-methylimidazolium complex exhibited an unusual 300 cm(-1) splitting in the D-5(0) -> F-7(1) transition, as reproduced by ligand field calculations, suggesting a stronger hydrogen bonding due to the smaller substituent. We hypothesize that this strong bonding likely causes angular distortions, resulting in high ligand field splittings.
keywords
INTRAMOLECULAR ENERGY-TRANSFER; BETA-DIKETONATE COMPLEX; CRYSTAL-FIELD; SPECTROSCOPIC PROPERTIES; PHOTOPHYSICAL PROPERTIES; 4F-4F TRANSITIONS; BASIS-SETS; LANTHANIDE; SPECTRA; LUMINESCENCE
subject category
Chemistry
authors
Blois, L; Costa, IF; Honorato, J; de Araújo, AS; Ando, RA; Neto, ANC; Suta, M; Malta, OL; Brito, HF
our authors
Albano Neto Carneiro Neto
Junior Researcheracknowledgements
The Article Processing Charge for the publication of this research was funded by the Coordination for the Improvement of Higher Education Personnel- CAPES (ROR identifier: 00x0ma614).