Photoionization of β-carotene via electron transfer from excited states to chlorinated hydrocarbon solvents. A picosecond transient absorption study

This work explores the concept that differential wave function overlap between excited states can be engineered within a molecular chromophore. The aim is to control excited state wave function symmetries, so that symmetry matches or mismatches result in differential orbital overlap and define low-energy trajectories or kinetic barriers within the excited state surface, that drive excited state population toward different reaction pathways. Two donor–acceptor assemblies were explored, where visible light absorption prepares excited states of different wave function symmetry. These states could be resolved using transient absorption spectroscopy, thanks to wave function symmetry-specific photoinduced optical transitions. One of these excited states undergoes energy transfer to the acceptor, while another undertakes a back-electron transfer to restate the ground state. This differential behavior is possible thanks to the presence of kinetic barriers that prevent excited state equilibration. This strategy can be exploited to avoid energy dissipation in energy conversion or photoredox catalytic schemes.

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Subpicosecond transient absorption study of intermolecular electron transfer between solute and electron-donating solvents

The Journal of Physical Chemistry ◽

10.1021/j100199a039 ◽

1992 ◽

Vol 96 (20) ◽

pp. 8042-8048 ◽

Cited By ~ 67

Author(s):

Hideki Kandori ◽

Klaus Kemnitz ◽

Keitaro Yoshihara

Keyword(s):

Electron Transfer ◽

Transient Absorption ◽

Absorption Study ◽

Intermolecular Electron Transfer

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Photoinduced electron transfer from colloidal cadmium sulfide to methylviologen: a picosecond transient absorption study

The Journal of Physical Chemistry ◽

10.1021/j100313a003 ◽

1988 ◽

Vol 92 (2) ◽

pp. 255-256 ◽

Cited By ~ 28

Author(s):

Yoshio Nosaka ◽

Hajime Miyama ◽

Mamoru Terauchi ◽

Takayoshi Kobayashi

Keyword(s):

Electron Transfer ◽

Cadmium Sulfide ◽

Photoinduced Electron Transfer ◽

Transient Absorption ◽

Absorption Study

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Excited-State Dynamics in the RNA Nucleotide Uridine 5’-Monophosphate Investigated by Femtosecond Broadband Transient Absorption Spectroscopy

10.26434/chemrxiv.7860023 ◽

2019 ◽

Author(s):

Matthew M. Brister ◽

Carlos Crespo-Hernández

Keyword(s):

Excited State ◽

Excited States ◽

Ground State ◽

Transient Absorption ◽

Electronic Energy ◽

Transient Absorption Spectroscopy ◽

Electronic Relaxation ◽

Vibrationally Excited ◽

Excited State Dynamics ◽

Π State

Damage to RNA from ultraviolet radiation induce chemical modifications to the nucleobases. Unraveling the excited states involved in these reactions is essential, but investigations aimed at understanding the electronic-energy relaxation pathways of the RNA nucleotide uridine 5’-monophosphate (UMP) have not received enough attention. In this Letter, the excited-state dynamics of UMP is investigated in aqueous solution. Excitation at 267 nm results in a trifurcation event that leads to the simultaneous population of the vibrationally-excited ground state, a longlived 1nOπ* state, and a receiver triplet state within 200 fs. The receiver state internally convert to the long-lived 3ππ* state in an ultrafast time scale. The results elucidate the electronic relaxation pathways and clarify earlier transient absorption experiments performed for uracil derivatives in solution. This mechanistic information is important because long-lived nπ* and ππ* excited states of both singlet and triplet multiplicities are thought to lead to the formation of harmful photoproducts.

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