A computational study of the vibronic effects on the electronic spectra and the photophysics of aza[7]helicene

2021 ◽  
Author(s):  
Yanli Liu ◽  
Daniel Aranda ◽  
Fabrizio Santoro
Keyword(s):  
Ground State ◽  
Electronic Spectra ◽  
Computational Study ◽  
High Fluorescence ◽  
Vibronic Effects ◽  
Photoinduced Processes

We report a computational study on vibronic effects in the spectroscopy, photoinduced processes and decay back to the ground state of aza[7]helicene, a helicene with an unusually high fluorescence quantum...

scholarly journals Photoprotective Properties of Eumelanin: Computational Insights into the Photophysics of a Catechol:Quinone Heterodimer Model System

Photochem ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 26-37
Author(s):  
Victoria C. Frederick ◽  
Thomas A. Ashy ◽  
Barbara Marchetti ◽  
Michael N. R. Ashfold ◽  
Tolga N. V. Karsili
Keyword(s):  
Ground State ◽  
Sandwich Structure ◽  
Computational Study ◽  
Minimum Energy ◽  
Carbonyl Oxygen ◽  
Model System ◽  
Molecular Structures ◽  
Uv Damage ◽  
Chromosomal Dna ◽  
Relevant Model

Melanins are skin-centered molecular structures that block harmful UV radiation from the sun and help protect chromosomal DNA from UV damage. Understanding the photodynamics of the chromophores that make up eumelanin is therefore paramount. This manuscript presents a multi-reference computational study of the mechanisms responsible for the experimentally observed photostability of a melanin-relevant model heterodimer comprising a catechol (C)–benzoquinone (Q) pair. The present results validate a recently proposed photoinduced intermolecular transfer of an H atom from an OH moiety of C to a carbonyl-oxygen atom of the Q. Photoexcitation of the ground state C:Q heterodimer (which has a π-stacked “sandwich” structure) results in population of a locally excited ππ* state (on Q), which develops increasing charge-transfer (biradical) character as it evolves to a “hinged” minimum energy geometry and drives proton transfer (i.e., net H atom transfer) from C to Q. The study provides further insights into excited state decay mechanisms that could contribute to the photostability afforded by the bulk polymeric structure of eumelanin.

scholarly journals Two-dimensional electronic spectroscopy as a tool for tracking molecular conformations in DNA/RNA aggregates

2018 ◽  
Vol 207 ◽  
pp. 233-250 ◽  
Author(s):  
Javier Segarra-Martí ◽  
Vishal K. Jaiswal ◽  
Ana Julieta Pepino ◽  
Angelo Giussani ◽  
Artur Nenov ◽  
...  
Keyword(s):  
Nucleic Acid ◽  
Ground State ◽  
Electronic Spectra ◽  
Crucial Role ◽  
Electronic Spectroscopy ◽  
Two Dimensional ◽  
Molecular Conformations ◽  
Computational Strategy

A computational strategy to simulate two-dimensional electronic spectra (2DES) is introduced, which allows characterising ground state conformations of flexible nucleobase aggregates that play a crucial role in nucleic acid photochemistry.

The electronic spectra of phenyl radicals

1965 ◽  
Vol 287 (1411) ◽  
pp. 457-470 ◽  
Keyword(s):  
Absorption Spectrum ◽  
Electronic Absorption Spectrum ◽  
Electronic Absorption ◽  
Ground State ◽  
Electronic Spectra ◽  
Flash Photolysis ◽  
Visible Region ◽  
Electronic Configuration ◽  
Vibrational Structure ◽  
Fundamental Frequencies

An electronic absorption spectrum, attributed to phenyl, has been observed in the visible region with origin at 18 908 cm -1 after flash photolysis of benzene and halogenobenzenes. Similar spectra of fluoro, chloro and bromo phenyl are observed after flash photolysis of disubstituted benzenes. The vibrational structure of the phenyl spectrum has been analysed in terms of two fundamental frequencies at 571 and 896 cm -1 which correspond to the e 2 g and a 1 g frequencies of the B 2 u state of benzene. The ground state of phenyl has a π 6 n electronic configuration and the observed transition is interpreted as 2 A 1 → 2 B 1 resulting from a π → n excitation.

scholarly journals Photoluminescence in m-carborane–anthracene triads: a combined experimental and computational study

2018 ◽  
Vol 6 (42) ◽  
pp. 11336-11347 ◽  
Author(s):  
Mahdi Chaari ◽  
Zsolt Kelemen ◽  
José Giner Planas ◽  
Francesc Teixidor ◽  
Duane Choquesillo-Lazarte ◽  
...  
Keyword(s):  
Computational Study ◽  
Fluorescence Emission ◽  
Fluorescence Properties ◽  
Quantum Yields ◽  
Aggregate State ◽  
Fluorescence Quantum Yields ◽  
High Fluorescence

m-Carborane has demonstrated to be a perfect platform to boost the fluorescence properties of anthracene, giving rise to high fluorescence quantum yields in solution and also retaining fluorescence emission in the aggregate state.

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