Efficient Ground-State Recovery of UV-Photoexcited p-Nitrophenol in Aqueous Solution by Direct and Multistep Pathways DOI Creative Commons
Deborin Ghosh, K. Eryn Spinlove, Hallam J. M. Greene

et al.

Journal of the American Chemical Society, Journal Year: 2024, Volume and Issue: 146(44), P. 30443 - 30454

Published: Oct. 25, 2024

Nitroaromatic compounds are found in brown carbon aerosols emitted to the Earth's atmosphere by biomass burning, and important organic chromophores for absorption of solar radiation. Here, transient spectroscopy spanning 100 fs–8 μs is used explore pH-dependent photochemical pathways aqueous solutions p-nitrophenol, chosen as a representative nitroaromatic compound. Broadband ultrafast UV–visible infrared probes characterize excited states intermediate species involved multistep photochemistry, determine their lifetimes under different pH conditions. The assignment bands, dynamical interpretation our experimental measurements supported computational calculations. After 320 nm photoexcitation first bright state, which has 1ππ* character Franck–Condon region, (∼200 fs) structural relaxation adiabatic S1 state region with 1nπ* electronic character, p-nitrophenol population decays on time scale ∼12 ps. This decay involves competition between direct internal conversion S0 (∼40%) rapid intersystem crossing triplet manifold (∼60%). Population T1-state excited-state proton transfer (ESPT) surrounding water resulting triplet-state p-nitrophenolate anion its ground ∼5 ns. Reprotonation S0-state recovers state. Overall recovery via these competing close 100% efficient. observations help explain why such resist photo-oxidative degradation environment.

Language: Английский

Efficient Ground-State Recovery of UV-Photoexcited p-Nitrophenol in Aqueous Solution by Direct and Multistep Pathways DOI Creative Commons
Deborin Ghosh, K. Eryn Spinlove, Hallam J. M. Greene

et al.

Journal of the American Chemical Society, Journal Year: 2024, Volume and Issue: 146(44), P. 30443 - 30454

Published: Oct. 25, 2024

Nitroaromatic compounds are found in brown carbon aerosols emitted to the Earth's atmosphere by biomass burning, and important organic chromophores for absorption of solar radiation. Here, transient spectroscopy spanning 100 fs–8 μs is used explore pH-dependent photochemical pathways aqueous solutions p-nitrophenol, chosen as a representative nitroaromatic compound. Broadband ultrafast UV–visible infrared probes characterize excited states intermediate species involved multistep photochemistry, determine their lifetimes under different pH conditions. The assignment bands, dynamical interpretation our experimental measurements supported computational calculations. After 320 nm photoexcitation first bright state, which has 1ππ* character Franck–Condon region, (∼200 fs) structural relaxation adiabatic S1 state region with 1nπ* electronic character, p-nitrophenol population decays on time scale ∼12 ps. This decay involves competition between direct internal conversion S0 (∼40%) rapid intersystem crossing triplet manifold (∼60%). Population T1-state excited-state proton transfer (ESPT) surrounding water resulting triplet-state p-nitrophenolate anion its ground ∼5 ns. Reprotonation S0-state recovers state. Overall recovery via these competing close 100% efficient. observations help explain why such resist photo-oxidative degradation environment.

Language: Английский

Citations

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