13ª Semana Integrada do Instituto de Física de São Carlos

Investigating optical non-linearities and triplet quantum yield in porphyrins-chalcone structures

21 de ago. de 2023 10:30

1h 30m

Salão de Eventos USP

Normal 10h30 - 12h00

Descrição

Porphyrin's molecular structure confers the ability to efficiently generate singlet oxygen, which is the primary cytotoxic agent responsible for the elimination of cancer cells, and this efficiency is related to the formation of molecules at the triplet long lifetime excited state. (1) Organic molecules exhibiting nonlinear optical responses have key advantages because of their potentially increasing depth of light penetration in tissue. (2) In this work, to complement the triplet study, we report on the study of two-photon absorption (TPA) spectra of a series of tetraphenyl porphyrin with chalcone derivatives groups in its neutral and cationic forms. It was expected that the electronic nature of porphyrins leads to a significant change in two-photon absorption cross-sections due to different electron-accepting groups and symmetry changes, influencing the TPA magnitude with distinct chalcone derivatives, which is extremely important in applications such as fluorescent bioprobes. (3) As it is known, so far, in the literature a few works report measurements on TPA cross-sections in porphyrins molecules, which is known to be difficult because of the easy aggregation of those at low molar concentrations. Thus, to circumvent this problem, we have set up a technique based on monitoring the fluorescence induced by a two-photon absorption that can be used for solutions at very low concentrations, avoiding aggregation.

Referências

1 MOURA, N. M. M. et al. A new synthetic approach to benzoporphyrins and Kröhnke type porphyrin-2-ylpyridines. Chemical Communications. v. 48, n. 49, p. 6142-6144, June 2012.

2 SRIVATSAN A. et al. Porphyrin-based photosensitizers and the corresponding multifunctional nanoplatforms for cancer-imaging and phototherapy. Journal of Porphyrins Phthalocyanines, v. 19, n. 1-3, p. 109-134, 2015.

3 LADEIRA, B. M. F. et al. Cationic pyrrolidine/pyrroline-substituted porphyrins as efficient photosensitizers against E. coli. Molecules, v. 26, n. 2, p. 464-1-464-17, Jan. 2021.