Synthesis, characterization and spectroscopic studies of binuclear lanthanide complexes containing the anti-inflammatory drug Ibuprofen and CH3-disubstituted bipyridine ligands: Influence of methyl group position in the photoluminescence.

The synthesis, solid state characterization, theoretical and experimental photoluminescence studies of two new important classes of binuclear lanthanide complexes: [Ln 2 (Ibf) 6 (4,4'-dmbpy) 2 ] Eu = 1 , Gd = 2 and Tb = 3 ) and [Ln 2 (Ibf) 6 (5,5'-dmbpy) 2 ] Eu = 4 , Gd = 5 and Tb = 6 ) (where: Ibf = non – steroidal anti – inflammatory drug (NSAID) Ibuprofen, 4,4'-dmbpy and 5,5'-dmbpy are 4,4'-dimethyl-2,2'-bipyridine and 5,5'-dimethyl-2,2'-bipyridine , respectively) are reported in this work. The analytical and spectroscopic data suggest the formation of binuclear compounds. The RM1 model was used to obtain the molecular structures of the Eu III complexes and its optimized ground state geometries were used to calculated all details involved in the energy transfer process and compared with experimental data, being in an optimal agreement. The lowest ligand triplet state (T 1 ) in these systems were obtained through of the time – resolved phosphorescence spectra, proving that the intramolecular energy transfer is responsible by high photoluminescence in these compounds. Still, the values of energy of the centroid of the 5 D 0 → 7 F 0 transition for the Eu III complexes, indicate an increase in the covalence degree for the Eu – L bonds, which is due to inductive effect (+I) of the –CH 3 groups in the ancillary ligands, when compared with those [Eu 2 (Ibf) 6 (bpy) 2 ] recently published. The high values of quantum efficiency and solubility in common organic solvents can opens the possibility to test this binuclear compounds in the field of efficient luminescent devices and biomarkers. [ABSTRACT FROM AUTHOR]