Propriedades estruturais e luminescentes de novos compostos carboxilatos e β-dicetonatos de íons lantanídeos

Abstract

In this research, two independent studies were conducted to investigate new lanthanide ion based compounds using carboxylate and β-diketonate ligands as luminescence sensitizers. In the first class, two different types of systems were explored: N-phthaloylglycine (phtgly) with N-(2-carboxybenzoyl) glycine (cbgly) or terephthalic acid (1,4-bdc), resulting in the formation of coordination polymers (CPs) with general formulas: {{[Ln2(phthgly)6(H2O)2]⋅(H2O)2}, {[Ln(phthgly)(cbgly)(H2O)2].(H2O)}, and {[Ln2(phthgly)4(bdc)(H2O)6](H2O)4}∞, as well as doped systems {[EuxTb1-x(phthgly)(cbgly)(H2O)2].(H2O)} (x= 0.25, 0.50, 0.75). On the other hand, the class of β-diketonate was used with auxiliary ligands, resulting in the formation of coordination compounds with general formulas [Ln(dbm)2(NO3)(L)2] and [Ln(dpm)(NO3)2(tchpo)2], where Ln: Eu3+, Tb3+, and Gd3+ and β-diketonate is represented by dbm: 2-diphenylmethane, dpm: dipivaloylmethane. The auxiliary ligands L include: tchpo (tricyclohexylphosphine oxide), topo (trioctylphosphine oxide), and tpAsO (triphenylarsine oxide). The synthesized systems were characterized using elemental microanalysis of C, H, and N, infrared absorption spectroscopy (FT-IR), diffuse reflectance, thermogravimetric analysis and nuclear magnetic resonance spectroscopy (NMR). Furthermore, the complexes {[Ln2(phthgly)6(H2O)2]⋅(H2O)2}, {[Ln2(phthgly)4(bdc)(H2O)6](H2O)4}∞, [Ln(dbm)2(NO3)(L)2] and [Ln(dpm)(NO3)2(tchpo)2] were obtained as single crystals, allowing their structures resolution by the single-crystal X-ray diffraction method. The luminescent properties were experimentally investigated based on spectral data of excitation, emission, and lifetime decay curves of the 5D0 emitting state and intrinsic quantum yield (𝑄𝐿𝑛𝐿𝑛). The spectra of the system {[Eu2(phthgly)4(bdc)(H2O)6](H2O)4}∞ showed that the intramolecular energy transfer processes are minimally operative, circumvented by the doping process with Tb3+ ions. Meanwhile, in the [Eu(dpm)(NO3)2(tchpo)2] system, very low luminescence intensity was observed due to an efficient luminescent quenching process via ligand-to-metal charge transfer (LMCT). Additionally, theoretical studies based on the Time-Dependent Density Functional Theory (TD-DFT) calculations, using the CAM-B3LYP functional and DKH2 relativistic Hamiltonian, together with results obtained from calculations using the JOYSpectra platform corroborated the experimental results. Based on these findings, new heteronuclear compounds of lanthanide ions with different carboxylate and β-diketonate ligands present potential for various applications.