Influence of electron-withdrawing groups in two-photon absorption of imidazopyridines derivatives
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2021
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This work investigates the influence of different electron-withdrawing groups (Cl, Br, fluorobenzonitrile), on the two-photon absorption cross-section of six imidazo[4,5-b]pyridine derivatives. The two-photon absorption cross-section spectra were obtained by ultra-fast Z-scan technique from 470 nm up to 700 nm. The Sum-Over-States approach was applied to model the two-photon absorption spectra, using a three-level energy system. Photophysical properties, such as transition dipole moment, the difference of permanent dipole moments, and anisotropy coefficient were determined through the analysis of one-photon absorption spectra, solvatochromism, and fluorescence anisotropy, respectively. Besides, the excited state absorption spectra were measured through ultra-fast transient absorption, allowing the excited state lifetime and spectral position determination. Two-photon absorption cross-sections of about 160 GM were observed when two electron-withdrawing groups are linked to the imidazo[4,5-b]pyridine core, elucidating a path to achieve high optical nonlinearities in imidazopyridine derivatives. Furthermore, a increase in the two-photon cross-section was observed when chloride is linked at the C-6 position (90 GM) instead of the C-5 position (50 GM), which is related to the proximity of a higher excited state.
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Imidazo[4,5-b]pyridines, Two-photon absorption, SOS model, Ultrafast transient absorption, Electron-withdrawing groups
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PELOSI, André Gasparotto et al. Influence of electron-withdrawing groups in two-photon absorption of imidazopyridines derivatives. Dyes and Pigments, Amsterdam, v. 198, e109972, 2021. DOI: 10.1016/j.dyepig.2021.109972. Disponível em: https://www.sciencedirect.com/science/article/pii/S014372082100838X. Acesso em: 29 fev. 2024.