Estudo sistemático da transferência de energia e de espectros de absorção em complexos de európio(III): aplicações da TDDFT e análise quimiométrica

Abstract

In this work, the performance of different TDDFT(Time-dependent density-functional theory) functionals in describing absorption spectra and energy transfer (ET) in Eu3+ complexes was evaluated. Initially, three β-diketonate complexes were studied: [Eu(DPTB)3(H2O)2] (Eu-1), [Eu(DPTB)3(BathPhen)] (Eu-2), and [Eu(hfaa)3(Nap-TerPyr)] (Eu-3), modeled using the DFT PBE0/TZVP/MWB52 method. TDDFT CAM-B3LYP results satisfactorily reproduced the experimental spectra of Eu-1 and Eu-2, with absorption dominated by β-diketonate ligands. ET occurred mainly through the T1→5D0 and T1→5D1 channels, with rates on the order of 107 s -1 . The higher sensitization efficiency of Eu-1 (η = 52.6%; exp.: 56.3%) compared to Eu-2 (η = 45.0%; exp.: 44.5%) was attributed to a lower T1→S0 deactivation rate. For Eu-3, Principal Component Analysis (PCA) grouped the functionals into three distinct clusters. The spectra predicted by PBE0, B1P, X3LYP, B1LYP, REVPBE0, TPSS0, PW1PW, mPW1PW, and mPW1LYP showed better agreement with experiment. The INDO/S-CIS method reproduced the spectrum well but significantly underestimated the T1 energy. TDDFT results indicated a relevant contribution of the neutral ligand to electronic absorption and of the β-diketonate ligands to ET via T1→Eu3+, with a calculated yield of 52.8% (exp.: 48.8%). Subsequently, the influence of methodological parameters on TDDFT spectra was investigated. PCA clustering of 122 experimental spectra revealed three distinct groups. The projection of theoretical spectra in PCA space, combined with Mahalanobis distances, indicated that the B3LYP functional is the most globally consistent among those studied. Therefore, it was adopted for the factorial design parameter study. The fractional factorial design (25-2 ) showed that the effects of basis set, number of excited states, use of TDA, implicit solvent, and dispersion depend on the spectral cluster: in group 1, effects were minimally relevant; in group 2, the absence of TDA improved agreement; and in group 3, dispersion corrections and absence of TDA were decisive for better reproduction of experimental profiles.