Sobre as diferenças nas propriedades fotoluminescentes dos complexos mononucleares e binucleares Eu/Tb-2-Hidroxibenzoato com 1,10-Fenantrolina : um estudo teórico-experimental

Abstract

This study presents a comprehensive investigation into the structural and luminescent properties of lanthanide 2-hydroxybenzoate compounds, focusing on Eu3+ and Tb3+ ions in both single and mixed systems. The X-ray structures of binuclear compound and mononuclearcompound were determined, both showing distinct triclinic crystal structures and coordinationgeometry. A comparative analysis of luminescent properties between these compounds unveiled significant differences in the nonradiative decay rates of the 5D0 level of Eu3+ ions, suggesting potential luminescence suppression channels. The investigation extended to mixed Eu3+-Tb3+ systems, demonstrating efficient Tb3+ to Eu3+ energy transfer, especially at room temperature. Three models, including two novel ones proposed in this study, were considered to model energy transfer in mixed systems. Our theoretical-experimental investigation reveals that variations in lifetimes of the emitting level 5D0 of Eu-2-OHBz mononuclear and binuclearcomplexes, or mixed Eu/Tb-2-OHBz complexes, with 1,10-phenanthrolines, primarily result from multiphonon decay processes. However, low-energy ligand-to-metal charge transfer (LMCT) states play a key role in suppressing luminescence in the binuclear Eu3+ complexes and Eu/Tb mixtures, compared to mononuclear analogues. Furthermore, the models also involve a rate equation, providing the theoretical absolute and intrinsic quantum yield, the latter showing discrepancy with experimentally measured data for the binuclear Eu3+ compound and excellent agreement for the mononuclear Eu3+, both at room temperature and at liquid nitrogen temperature.