Síntese, caracterização e estudo fotofísico de complexos de lantanídeos contendo ligantes cromóforos com potencial aplicação em dispositivos luminescentes

Abstract

In this work, new lanthanide complexes containing dicarboxylate ligands and neutral nitrogen ligands, as well as Eu(III) complexes containing β-diketone ligands and neutral nitrogen ligands, were synthesized and characterized for use in Light-Converting Molecular Devices (LCMDs). The complexes were characterized, and their luminescent properties were studied. These complexes exhibited distinct chemical structures with general formulas of [Ln(Furan)(44Dmbpy)(NO₃)]·2H₂O, [Ln₂(Biq)₃(DMF)₃(H₂O)]·DMF·2H₂O (Ln = Eu(III), Tb(III), and Gd(III), 44Dmbpy = 4,4’-dimethyl-2,2’-bipyridine, Furan = 2,5-furandicarboxylic acid, Biq = 2,2’-biquinoline-4,4’-dicarboxylic acid), and [Sm(Phen)(Chelo)(NO₃)(H₂O)] (Phen = phenanthroline, Chelo = chelidonic acid) for the dicarboxylates. For the β-diketonates, the complexes had the following formulas: [Eu(TFB)355Dmbpy], [Eu(TTA)355Dmbpy], [Eu₂(TTA)₈]²⁻·TMDP²⁺, [Eu(TTA)₃TMDP], [Eu(TFB)₃TMDP], [Eu(TFB)₄]⁻·(66Dmbpy)⁺, [Eu(TFB)₃Bato], and [Eu₂(TTA)₆Pyra] (TFB = 4,4,4-trifluoro-1-phenyl-1,3-butanedione, TTA = 2-thenoyltrifluoroacetone, 55Dmbpy = 5,5’-dimethyl-2,2’-bipyridine, TMDP = 4,4'- trimethylenedipyridine, 66Dmbpy = 6,6’-dimethyl-2,2’-bipyridine, Bato = bathophenanthroline, Pyra = pyrazinecarboxamide). The energy transfer process between the ligand→Ln(III) was studied through photoluminescent analyses, and the quantum efficiency (η) was calculated for the Eu(III) complexes. The β-diketonate complexes exhibited high quantum efficiency, with [Eu(TFB)355Dmbpy] achieving the highest quantum efficiency of 68.92%. Due to their high luminescence, the complexes [Eu(TFB)355Dmbpy] and [Eu(TTA)355Dmbpy] were used in OLEDs (organic light-emitting diodes) with different architectures, resulting in devices with high color purity and luminance. The most efficient OLEDs showed luminance of 883 and 2291 cd/m² for complexes [Eu(TFB)355Dmbpy] e [Eu(TTA)355Dmbpy], respectively. The [Eu(TFB)₄]⁻·(66Dmbpy)⁺ complex, having an ionic character, was used in the fabrication of LECs (light-emitting electrochemical cells), exhibiting luminescent properties. However, the emission was imperceptible to the human eye due to the low efficiency of the device.