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Brandl, Fabian ; Bergwinkl, Sebastian ; Allacher, Carina ; Dick, Bernhard

Consecutive photoinduced electron transfer (conPET): The mechanism of the photocatalyst rhodamine-6G

Brandl, Fabian, Bergwinkl, Sebastian, Allacher, Carina und Dick, Bernhard (2020) Consecutive photoinduced electron transfer (conPET): The mechanism of the photocatalyst rhodamine-6G. Chemistry - A European Journal 26, S. 7946-7954.

Veröffentlichungsdatum dieses Volltextes: 22 Jan 2021 08:43
Artikel
DOI zum Zitieren dieses Dokuments: 10.5283/epub.44560


Zusammenfassung

The dye rhodamine 6G can act as a photocatalyst through photoinduced electron transfer. After electronic excitation with green light, rhodamine 6G takes an electron from an electron donor, such as N,N-diisopropylethylamine, and forms the rhodamine 6G radical. This radical has a reduction potential of around -0.90 V and can split phenyl iodide into iodine anions and phenyl radicals. Recently, it ...

The dye rhodamine 6G can act as a photocatalyst through photoinduced electron transfer. After electronic excitation with green light, rhodamine 6G takes an electron from an electron donor, such as N,N-diisopropylethylamine, and forms the rhodamine 6G radical. This radical has a reduction potential of around -0.90 V and can split phenyl iodide into iodine anions and phenyl radicals. Recently, it has been reported that photoexcitation of the radical at 420 nm splits aryl bromides into bromide anions and aryl radicals. This requires an increase in reduction potential, hence the electronically excited rhodamine 6G radical was proposed as the reducing agent. Here, we present a study of the mechanism of the formation and photoreactions of the rhodamine 6G radical by transient absorption spectroscopy in the time range from femtoseconds to minutes in combination with quantum chemical calculations. We conclude that one photon of 540 nm light produces two rhodamine 6G radicals. The lifetime of the photoexcited radicals of around 350 fs is too short to allow diffusion-controlled interaction with a substrate. A fraction of the excited radicals ionize spontaneously, presumably producing solvated electrons. This decay produces hot rhodamine 6G and hot rhodamine 6G radicals, which cool with a time constant of around 10 ps. In the absence of a substrate, the ejected electrons recombine with rhodamine 6G and recover the radical on a timescale of nanoseconds. Photocatalytic reactions occur only upon excitation of the rhodamine 6G radical, and due to its short excited-state lifetime, the electron transfer to the substrate probably takes place through the generation of solvated electrons as an additional step in the proposed photochemical mechanism.



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Details

DokumentenartArtikel
Titel eines Journals oder einer ZeitschriftChemistry - A European Journal
Verlag:Wiley
Ort der Veröffentlichung:WEINHEIM
Band:26
Seitenbereich:S. 7946-7954
Datum2020
InstitutionenChemie und Pharmazie > Institut für Physikalische und Theoretische Chemie
Chemie und Pharmazie > Institut für Physikalische und Theoretische Chemie > Chair of Chemistry III - Physical Chemistry (Molecular Spectroscopy and Photochemistry)
Chemie und Pharmazie > Institut für Physikalische und Theoretische Chemie > Chair of Chemistry III - Physical Chemistry (Molecular Spectroscopy and Photochemistry) > Prof. Dr. Bernhard Dick
Identifikationsnummer
WertTyp
10.1002/chem.201905167DOI
Stichwörter / KeywordsHYDRATED ELECTRONS; CATALYTIC CYCLE; LIGHT; ABSORPTION; SPECTROSCOPY; DYES; density functional calculations; electron transfer; photocatalysis; reaction mechanisms; time-resolved spectroscopy
Dewey-Dezimal-Klassifikation500 Naturwissenschaften und Mathematik > 540 Chemie
StatusVeröffentlicht
BegutachtetJa, diese Version wurde begutachtet
An der Universität Regensburg entstandenJa
URN der UB Regensburgurn:nbn:de:bvb:355-epub-445601
Dokumenten-ID44560

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