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Article: How and When Does an Unusual and Efficient Photoredox Reaction of 2-(1-Hydroxyethyl) 9,10-Anthraquinone Occur? A Combined Time-Resolved Spectroscopic and DFT Study

TitleHow and When Does an Unusual and Efficient Photoredox Reaction of 2-(1-Hydroxyethyl) 9,10-Anthraquinone Occur? A Combined Time-Resolved Spectroscopic and DFT Study
Authors
Issue Date2012
PublisherAmerican Chemical Society. The Journal's web site is located at http://pubs.acs.org/journals/jacsat/index.html
Citation
Journal of the American Chemical Society, 2012, v. 134 n. 36, p. 14858-14868 How to Cite?
AbstractThe photophysics and photochemical reactions of 2-(1-hydroxyethyl) 9,10-anthroquinone (2-HEAQ) were studied using femtosecond transient absorption (fs-TA), nanosecond transient absorption (ns-TA), and nanosecond time-resolved resonance Raman (ns-TR(3)) spectroscopy techniques and density functional theory (DFT) calculations. In acetonitrile, 2-HEAQ underwent efficient intersystem crossing to the triplet excited state ((2-HEAQ)(3)). A typical photoreduction reaction for aromatic ketones took place via production of a ketyl radical intermediate for 2-HEAQ in isopropanol. In water-containing solutions with pH values between 2 and 10, an unusual photoredox reaction reported by Wan and co-workers was detected and characterized. Observation of the protonated species in neutral and acidic aqueous solutions by fs-TA spectra indicated the carbonyl oxygen of (2-HEAQ)(3) was protonated initially and acted as a precursor of the photoredox reaction. The preference of the photoredox reaction to occur under moderate acidic conditions compared to neutral condition observed using ns-TR(3) spectroscopy was consistent with results from DFT calculations, which suggested protonation of the carbonyl group was the rate-determining step. Under stronger acidic conditions (pH 0), although the protonated (2-HEAQ)(3) was formed, the predominant reaction was the photohydration reaction instead of the photoredox reaction. In stronger basic solutions (pH 12), (2-HEAQ)(3) decayed with no obvious photochemical reactions detected by time-resolved spectroscopic experiments. Reaction mechanisms and key reactive intermediates for the unusual photoredox reaction were elucidated from time-resolved spectroscopy and DFT results. A brief discussion is given of when photoredox reactions may likely take place in the photochemistry of aromatic carbonyl-containing compounds and possible implications for using BP and AQ scaffolds for phototrigger compounds.
Persistent Identifierhttp://hdl.handle.net/10722/188227
ISSN
2015 Impact Factor: 13.038
2015 SCImago Journal Rankings: 7.123
ISI Accession Number ID

 

DC FieldValueLanguage
dc.contributor.authorMa, J-
dc.contributor.authorSu, T-
dc.contributor.authorLi, MD-
dc.contributor.authorDu, W-
dc.contributor.authorHuang, J-
dc.contributor.authorGuan, X-
dc.contributor.authorPhillips, DL-
dc.date.accessioned2013-08-23T03:13:15Z-
dc.date.available2013-08-23T03:13:15Z-
dc.date.issued2012-
dc.identifier.citationJournal of the American Chemical Society, 2012, v. 134 n. 36, p. 14858-14868-
dc.identifier.issn0002-7863-
dc.identifier.urihttp://hdl.handle.net/10722/188227-
dc.description.abstractThe photophysics and photochemical reactions of 2-(1-hydroxyethyl) 9,10-anthroquinone (2-HEAQ) were studied using femtosecond transient absorption (fs-TA), nanosecond transient absorption (ns-TA), and nanosecond time-resolved resonance Raman (ns-TR(3)) spectroscopy techniques and density functional theory (DFT) calculations. In acetonitrile, 2-HEAQ underwent efficient intersystem crossing to the triplet excited state ((2-HEAQ)(3)). A typical photoreduction reaction for aromatic ketones took place via production of a ketyl radical intermediate for 2-HEAQ in isopropanol. In water-containing solutions with pH values between 2 and 10, an unusual photoredox reaction reported by Wan and co-workers was detected and characterized. Observation of the protonated species in neutral and acidic aqueous solutions by fs-TA spectra indicated the carbonyl oxygen of (2-HEAQ)(3) was protonated initially and acted as a precursor of the photoredox reaction. The preference of the photoredox reaction to occur under moderate acidic conditions compared to neutral condition observed using ns-TR(3) spectroscopy was consistent with results from DFT calculations, which suggested protonation of the carbonyl group was the rate-determining step. Under stronger acidic conditions (pH 0), although the protonated (2-HEAQ)(3) was formed, the predominant reaction was the photohydration reaction instead of the photoredox reaction. In stronger basic solutions (pH 12), (2-HEAQ)(3) decayed with no obvious photochemical reactions detected by time-resolved spectroscopic experiments. Reaction mechanisms and key reactive intermediates for the unusual photoredox reaction were elucidated from time-resolved spectroscopy and DFT results. A brief discussion is given of when photoredox reactions may likely take place in the photochemistry of aromatic carbonyl-containing compounds and possible implications for using BP and AQ scaffolds for phototrigger compounds.-
dc.languageeng-
dc.publisherAmerican Chemical Society. The Journal's web site is located at http://pubs.acs.org/journals/jacsat/index.html-
dc.relation.ispartofJournal of the American Chemical Society-
dc.subject.meshAnthraquinones - chemical synthesis - chemistry-
dc.subject.meshMolecular Structure-
dc.subject.meshOxidation-Reduction-
dc.subject.meshPhotochemical Processes-
dc.subject.meshQuantum Theory-
dc.titleHow and When Does an Unusual and Efficient Photoredox Reaction of 2-(1-Hydroxyethyl) 9,10-Anthraquinone Occur? A Combined Time-Resolved Spectroscopic and DFT Studyen_US
dc.typeArticleen_US
dc.identifier.emailPhillips, DL: phillips@hku.hk-
dc.identifier.doi10.1021/ja304441n-
dc.identifier.pmid22909212-
dc.identifier.hkuros220087-
dc.identifier.volume134-
dc.identifier.issue36-
dc.identifier.spage14858-
dc.identifier.epage14868-
dc.identifier.isiWOS:000308574800044-
dc.publisher.placeUnited States-

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