Excited-state dynamics of 3,3′-dihydroxyisorenieratene and (3R,3′R)-zeaxanthin: Observation of vibrationally hot S0 species
Autor: | Florian Ehlers, Mirko Scholz, Kawon Oum, Thomas Lenzer |
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Rok vydání: | 2018 |
Předmět: |
Materials science
Biophysics Time constant Substituent Quantum yield 02 engineering and technology 010402 general chemistry 021001 nanoscience & nanotechnology Photochemistry Internal conversion (chemistry) 01 natural sciences Biochemistry 0104 chemical sciences 3. Good health chemistry.chemical_compound chemistry Excited state Ultrafast laser spectroscopy Molecule Absorption (chemistry) 0210 nano-technology Molecular Biology |
Zdroj: | Archives of Biochemistry and Biophysics. 646:137-144 |
ISSN: | 0003-9861 |
Popis: | We report on an ultrafast transient absorption study of all-trans-3,3′-dihydroxyisorenieratene (“DHIR”) and all-trans-(3R,3′R)-zeaxanthin in organic solvents covering the wavelength range 350–770 nm. The lifetime of the S2 state in both carotenoids is 160–170 fs. Upon internal conversion (IC) non-equilibrated S1 molecules are formed which internally relax on a 300–400 fs time scale. The time constant for IC from S1 depends on the type of terminal substituent: Replacement of the two terminal β-ionone rings of zeaxanthin by two aryl rings in DHIR results in an increase from 9.5 to 10.9 ps in THF. This suggests a mild decrease in the effective conjugation length of DHIR. IC to the ground electronic state prepares vibrationally hot S0* molecules which exhibit characteristic bleach and absorption bands. These are typically denoted as “S* features”. Collisional cooling of S0* happens with a time constant of 15 ps. Based on our results and the findings from previous studies for other carotenoids, such as macro-β-carotenes, β-carotenes and long-chain apocarotenals, we conclude that S0* spectral features are ubiquitous in carotenoid photophysics: They are particularly easy to observe in systems with a very short S1 lifetime and a high quantum yield for IC to the ground electronic state. |
Databáze: | OpenAIRE |
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