Banca de QUALIFICAÇÃO: JORGE ADRIANO ALVES COELHO

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : JORGE ADRIANO ALVES COELHO
DATE: 26/08/2021
LOCAL: Programa de Pós-Graduação em Ciência de Materiais (on-line)
TITLE:

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

KEY WORDS:

energy transfer, lanthanides, transition metals, d-f heterometallic complexes

PAGES: 103
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUMMARY:

There is a growing interest in alternatives to lanthanide ions (Ln³⁺) luminescence sensitizing chromophores for in vivo usage, mainly in the optical biological windows. Transition metals (M) are good candidates as chromophores as they have high absorption rates and emission bands covering a wide range of visible to near-infrared spectrum. However, despite the importance of theoretical models for the development of more efficient M-Ln³⁺ complexes, few works have been devoted efforts to elucidating the energy transfer process (ET) between the M and Ln³⁺ ions. In this context, this work aims to adapt and apply the intramolecular energy transfer theories developed by Malta and collaborators to treat ET between M–Ln³⁺ in heterometallic complexes. As an example, the new model can estimate the ET rates between Cr³⁺ and Ln³⁺ ions. The work also aims to verify whether the ET model for isotropic exchange interaction can be used between the M and Ln³⁺ ions, by investigating the orbital overlap between the valence subshells of the transition metal and the 4f  subshell of the Ln³⁺ ions. DFT-based calculations of overlap integrals associated with the diatomic-like pairs M-Ln³⁺ are presented. Parameters such as dipole strength (S_D) and spectral overlap factor (F) were calculated from the spectroscopic data available in the literature for the studied data and the theoretical intensity parameters (Ω_λ)  were calculated with the JOYSpectra program. The estimated values for the ET rates with the proposed model were compared with the experimental results available for several complexes M-Ln³⁺, such as containing Cr³⁺ and Ln³⁺ ions. The results showed that the exchange interaction is negligible for the typical intermetallic distances (> 5 Å) in M-Ln³⁺ complexes. On the other hand, the results for theoretical estimates of ET, considering the dipole-dipole and dipole-multipole mechanisms, in general, are in agreement with the experimental data available for the studied cases, mainly in situations where the donor and acceptor states are resonant. Under low resonance conditions, such as the Cr-Yb case, the models were extended to consider phonon assistance in ET. The fit of the model to the experimental data was obtained for Huang-Rhys factor values within the typical ranges expected for lanthanides and for the Cr³⁺ ion. At the present stage, the proposed model can be useful to predict and explain photophysical properties guided by the energy transfer between the transition metal and the Ln³⁺ ion.

BANKING MEMBERS:
Presidente - 2376051 - EDILSON LUCENA FALCAO FILHO
Externo à Instituição - ADELMO SATURNINO DE SOUZA
Externo à Instituição - RENALDO TENORIO DE MOURA JUNIOR - UFPB