Banca de DEFESA: JORGE ADRIANO ALVES COELHO

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : JORGE ADRIANO ALVES COELHO
DATE: 09/11/2023
TIME: 14:00
LOCAL: Programa de Pós-Graduação em Ciência de Materiais
TITLE:

Theoretical analysis of energy transfer between transition metals and lanthanides in heterometallic complexes

KEY WORDS:

energy transfer, lanthanides, transition metals, heterometallic complexes d-f, phonon assisted energy transfer.

PAGES: 118
BIG AREA: Outra
AREA: Multidisciplinar
SUMMARY:

There is an increasing interest in alternatives to the sensitizers of lanthanides ions (Ln3+) for in vivo usage, especially in bio-optical applications. The transition metals (M) are good candidates as chromophores, due to their high absorption rates, and their emission bands that cover a large range of visible, and Near Infrared spectra. Despite the importance of theoretical models for the design of M-Ln3+ with higher efficiency, few works had dedicated efforts to theoretically elucidate the process of Energy Transfer (ET) between M and Ln3+ ions. In this sense, this work has the goal to adapt and apply the theory of intramolecular energy transfer developed by Malta, and collaborators to treat with ET in M-Ln3+ heterometallic complexes. Additionally, another goal is to evaluate the ET model for isotropic exchange interaction between M, and Ln3+ ions, by investigating the overlap orbital of the valence's subshell of the transition metal with the 4f subshells of the Ln3+. The overlap integrals were calculated by the coefficients of molecular orbitals for the diatomic M-Ln3+, acquired in the DFT calculations. Parameters such as the dipole strength, and the overlap spectral factor (F factor) were calculated based on the spectroscopic data available in the literature for the complexes considered. Moreover, the theoretical intensity parameters (Ωλ) were calculated by using the web application JOYSpectra. The results have shown that the exchange interaction is not relevant for typical intermetallic distances (> 5 Å) in complexes of M-Ln3+. On the other hand, the theoretical estimations of ET rates for the dipole-dipole, and dipole-quadrupole mechanisms were in reasonable agreement with the energy transfer rates observed in the systems evaluated, especially in the cases with spectral resonance (complexes of Cr-Nd, Ru-Nd). For the systems that have low spectral resonance, such as the ones with Cr-Eu, and Cr-Yb, the model was extended to consider the phonon assistance in the energy transfer process, based on the approach of Miyakawa-Dexter. The fit of the experimental data was gained for the typical values of Huang-Rhys factors of the lanthanide and Cr3+ ions. In the current stage, the model provided can be useful to predict and explain photophysical properties driven by the transfer of energy between the Ln3+, and transition metal ions.

COMMITTEE MEMBERS:
Interno - 1129726 - CID BARTOLOMEU DE ARAUJO
Externo à Instituição - HERMI FELINTO DE BRITO - USP
Presidente - 1130924 - OSCAR MANOEL LOUREIRO MALTA
Externo à Instituição - SIDNEY JOSE LIMA RIBEIRO - UNESP
Externo à Instituição - WAGNER DE MENDONCA FAUSTINO - UFPB