First Eu3+, Gd3+ and Tb3+ complexes containing the non-steroidal anti-inflammatory drug ketoprofen and N,N-donors ligands: Synthesis, solid state characterization and photoluminescence studies

Reports on lanthanide complexes derived from non-steroidal anti-inflammatory drug molecules are still quite scarce in the literature, despite the potential properties of these molecules as therapeutic agents and biological markers. The current literature reports only lanthanide compounds containing the ketoprofenate ligand, most of the time containing coordination water molecules, which causes serious luminescence suppression. This study reports three new classes of highly photoluminescent lanthanide ketoprofenates with general formulas [Ln2(keto)6(bpy)2] (1)–(3), [Ln2(keto)6(phen)2] (4)–(6) and [Ln2(keto)6(4,4′-dmbpy)2] (7)–(9) (where: Ln = Eu3+, Gd3+ e Tb3+; keto = ketoprofenate anion, bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline and 4,4′-dmbpy = 4,4′-dimethyl-2,2′-bipyridine). These nine complexes were fully characterized and the photophysical studies were carried out in detail. Furthermore, the energy transfer mechanism was completely elucidated with the aid of theoretical calculations using the Sparkle/RM1 method, closely related to the nature of the employed ancillary ligand. The calculated luminescence spectroscopic parameters are in excellent agreement with those obtained experimentally, reinforcing the homobimetallic structure for these complexes. With the highest values of quantum efficiencies ( %η) ever reported for lanthanide ketoprofenates, these compounds comprise potential molecules for use as biological markers or anti-inflammatory agents.