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Article: Ultrafast time-resolved study of photophysical processes involved in the photodeprotection of p-hydroxyphenacyl caged phototrigger compounds

TitleUltrafast time-resolved study of photophysical processes involved in the photodeprotection of p-hydroxyphenacyl caged phototrigger compounds
Authors
Issue Date2005
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, 2005, v. 127 n. 5, p. 1463-1472 How to Cite?
AbstractA combined femtosecond Kerr gated time-resolved fluorescence (fs-KTRF) and picosecond Kerr gated time-resolved resonance Raman (ps-KTR3) study is reported for two p-hydroxyphenacyl (pHP) caged phototriggers, HPDP and HPA, in neat acetonitrile and water/acetonitrile (1:1 by volume) solvents. Fs-KTRF spectroscopy was employed to characterize the spectral properties and dynamics of the singlet excited states, and the ps-KTR3 was used to monitor the formation and subsequent reaction of triplet state. These results provide important evidence for elucidation of the initial steps for the pHP deprotection mechanism. An improved fs-KTRF setup was developed to extend its detectable spectral range down to the 270 nm UV region while still covering the visible region up to 600 nm. This combined with the advantage of KTRF in directly monitoring the temporal evolution of the overall fluorescence profile enables the first time-resolved observation of dual fluorescence for pHP phototriggers upon 267 nm excitation. The two emitting components were assigned to originate from the 1ππ * (S3) and 1nπ * (S1) states, respectively. This was based on the lifetime, the spectral location, and how these varied with the type of solvent. By correlating the dynamics of the singlet decay with the triplet formation, a direct 1nπ* → 3π * ISC mechanism was found for these compounds with the ISC rate estimated to be ∼5 × 10 11 s-1 in both solvent systems. These photophysical processes were found to be little affected by the kind of leaving group indicating the common local pHP chromophore is largely responsible for the fluorescence and relevant deactivation processes. The triplet lifetime was found to be ∼420 and 2130 ps for HPDP and HPA, respectively, in the mixed solvent compared to 150 and 137 ns, respectively, in neat MeCN. The solvent and leaving group dependent quenching of the triplet is believed to be associated with the pHP deprotection photochemistry and indicates that the triplet is the reactive precursor for pHP photorelease reactions for the compounds examined in this study.
Persistent Identifierhttp://hdl.handle.net/10722/68794
ISSN
2015 Impact Factor: 13.038
2015 SCImago Journal Rankings: 7.123
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorMa, Cen_HK
dc.contributor.authorWai, MKen_HK
dc.contributor.authorWing, SCen_HK
dc.contributor.authorZuo, Pen_HK
dc.contributor.authorKan, JTWen_HK
dc.contributor.authorToy, PHen_HK
dc.contributor.authorPhillips, DLen_HK
dc.date.accessioned2010-09-06T06:07:47Z-
dc.date.available2010-09-06T06:07:47Z-
dc.date.issued2005en_HK
dc.identifier.citationJournal Of The American Chemical Society, 2005, v. 127 n. 5, p. 1463-1472en_HK
dc.identifier.issn0002-7863en_HK
dc.identifier.urihttp://hdl.handle.net/10722/68794-
dc.description.abstractA combined femtosecond Kerr gated time-resolved fluorescence (fs-KTRF) and picosecond Kerr gated time-resolved resonance Raman (ps-KTR3) study is reported for two p-hydroxyphenacyl (pHP) caged phototriggers, HPDP and HPA, in neat acetonitrile and water/acetonitrile (1:1 by volume) solvents. Fs-KTRF spectroscopy was employed to characterize the spectral properties and dynamics of the singlet excited states, and the ps-KTR3 was used to monitor the formation and subsequent reaction of triplet state. These results provide important evidence for elucidation of the initial steps for the pHP deprotection mechanism. An improved fs-KTRF setup was developed to extend its detectable spectral range down to the 270 nm UV region while still covering the visible region up to 600 nm. This combined with the advantage of KTRF in directly monitoring the temporal evolution of the overall fluorescence profile enables the first time-resolved observation of dual fluorescence for pHP phototriggers upon 267 nm excitation. The two emitting components were assigned to originate from the 1ππ * (S3) and 1nπ * (S1) states, respectively. This was based on the lifetime, the spectral location, and how these varied with the type of solvent. By correlating the dynamics of the singlet decay with the triplet formation, a direct 1nπ* → 3π * ISC mechanism was found for these compounds with the ISC rate estimated to be ∼5 × 10 11 s-1 in both solvent systems. These photophysical processes were found to be little affected by the kind of leaving group indicating the common local pHP chromophore is largely responsible for the fluorescence and relevant deactivation processes. The triplet lifetime was found to be ∼420 and 2130 ps for HPDP and HPA, respectively, in the mixed solvent compared to 150 and 137 ns, respectively, in neat MeCN. The solvent and leaving group dependent quenching of the triplet is believed to be associated with the pHP deprotection photochemistry and indicates that the triplet is the reactive precursor for pHP photorelease reactions for the compounds examined in this study.en_HK
dc.languageengen_HK
dc.publisherAmerican Chemical Society. The Journal's web site is located at http://pubs.acs.org/journals/jacsat/index.htmlen_HK
dc.relation.ispartofJournal of the American Chemical Societyen_HK
dc.titleUltrafast time-resolved study of photophysical processes involved in the photodeprotection of p-hydroxyphenacyl caged phototrigger compoundsen_HK
dc.typeArticleen_HK
dc.identifier.openurlhttp://library.hku.hk:4550/resserv?sid=HKU:IR&issn=0002-7863&volume=127&issue=5&spage=1463&epage=1472&date=2005&atitle=Ultrafast+time-resolved+study+of+photophysical+processes+involved+in+the+photodeprotection+of+p-Hydroxyphenacyl+caged+phototrigger+compoundsen_HK
dc.identifier.emailMa, C:macs@hkucc.hku.hken_HK
dc.identifier.emailToy, PH:phtoy@hkucc.hku.hken_HK
dc.identifier.emailPhillips, DL:phillips@hku.hken_HK
dc.identifier.authorityMa, C=rp00758en_HK
dc.identifier.authorityToy, PH=rp00791en_HK
dc.identifier.authorityPhillips, DL=rp00770en_HK
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1021/ja0458524en_HK
dc.identifier.pmid15686379-
dc.identifier.scopuseid_2-s2.0-13444278566en_HK
dc.identifier.hkuros98518en_HK
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-13444278566&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume127en_HK
dc.identifier.issue5en_HK
dc.identifier.spage1463en_HK
dc.identifier.epage1472en_HK
dc.identifier.isiWOS:000226843900039-
dc.publisher.placeUnited Statesen_HK
dc.identifier.scopusauthoridMa, C=7402924979en_HK
dc.identifier.scopusauthoridWai, MK=8761955300en_HK
dc.identifier.scopusauthoridWing, SC=8761955400en_HK
dc.identifier.scopusauthoridZuo, P=35068878800en_HK
dc.identifier.scopusauthoridKan, JTW=8753189200en_HK
dc.identifier.scopusauthoridToy, PH=7006579247en_HK
dc.identifier.scopusauthoridPhillips, DL=7404519365en_HK

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