Novos compostos bis-dipivaloilmetanato de íons lantanídeos trivalentes: síntese, caracterização e transferência de energia

Abstract

This work reports the synthesis, characterization and the investigation of photoluminescence properties of systems [Ln(DPM)2(NO3)(L)2] and [Ln(L)3(NO3)3] (where L = THPO or TPPO and Ln3+ = Tb3+, Gd3+ or Eu3+), and the dimeric compounds [Eu2(DPM)6] and [Tb2(DPM)6]. The compounds were characterized by elemental analysis of CHN, vibrational spectroscopy in the infrared region, thermogravimetric analysis and their spectroscopic properties were investigated by molecular diffuse reflectance, excitation and emission as well as decay times of emitting states. The experimental data of CHN analysis and complexometric titrations of the synthesized complexes are in agreement with theoretical data for their respective formulas. The absorption spectra in the infrared region show that the coordination of β-diketonate and phosphine oxide ligands to the Ln3+ ions occurs by the oxygen atoms of carbonyl groups and P=O, respectively. The structural behavior of complexes [Eu(DPM)2(NO3)(TPPO)2] and [Tb (DPM)2(NO3)(TPPO)2] is significantly different from those dimeric ones [Eu2(DPM)6] and [Tb2(DPM)6]. In addition, the complex [Tb(DPM)2(NO3)(TPPO)2] presented fractoluminescence phenomenon, emitting green light when its crystals are broken. The presence of metal ligand charge transfer state (TCLM) of low energy in compounds of Eu3+ was also investigated. The luminescent properties studies showed that the bis-DPM systems Eu3+, an increase occurs in the energy state of TCLM, contributing to an increase in luminescence intensity of these compounds, when compared with dimeric complexes. This observation is evidenced by the luminescence at room temperature observed for the first compound, which is not observed for the second. The geometries of complexes [Ln2(DPM)6] and [Ln(DPM)2(NO3)(L)2] with Ln = Tb3+ or Eu3+ were optimized using SPARKLE/RM1 method, the first having a coordination polyhedron described by a monocapped trigonal prism trigonal and the second as distorted dodecahedron.