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Article: A theoretical investigation of p-hydroxyphenacyl caged phototrigger compounds: An examination of the excited state photochemistry of p-hydroxyphenacyl acetate

TitleA theoretical investigation of p-hydroxyphenacyl caged phototrigger compounds: An examination of the excited state photochemistry of p-hydroxyphenacyl acetate
Authors
Issue Date2006
PublisherAmerican Chemical Society. The Journal's web site is located at http://pubs.acs.org/jpca
Citation
Journal Of Physical Chemistry A, 2006, v. 110 n. 45, p. 12406-12413 How to Cite?
AbstractAb initio and density functional theory methods were employed to study the excited states and potential energy surfaces of the p-hydoxyphenacyl acetate (HPA) phototrigger compound. Complete active space (CAS) ab initio calculations predicted adiabatic electronic transition energies for the HPA-T 1( 3nπ*), HPA-T 2( 3ππ*), HPA-S 1( 1nπ*), HPA-T 3( 3nπ*), HPA-S 2( 1nπ*), HPA-S 3( 1ππ*) ← HPA-S 0 transitions that were similar to and in agreement with those found experimentally for closely related aromatic ketones such as p-hydroxyacetophenone and results from similar calculations for other related aromatic carbonyl systems. The α or β bond cleavage reactions from the S 1 excited state were both found to have relatively high barriers to reaction, and the S 1, T 1, and T 2 states are close in energy with the three S 1( 1nπ*), T 1( 3nπ*), and T 2( 3ππ*) surfaces intersecting at the same region. The calculations suggest that intersystem crossing (ISC) can occur very fast from the S 1 state to the nearby triplet states. This is consistent with results from ultrafast spectroscopy experiments that observe the S 1 state ISC occurs within about 1-2 ps to produce a triplet state for HPA and related pHP compounds. The α and β bond cleavage reactions for the T 1 state of HPA are both predicted to have fairly high barriers and compete with one another. However, this is not completely consistent with experiments that observe the photodeprotection reactions (e.g. the β bond cleavage) of HPA and some other pHP phototriggers in largely water containing solvents are predominant and occur very fast to release the leaving group. Comparison of the computational results with experimental results for HPA and related pHP compounds suggests that water molecules likely play an important part in changing the triplet state β bond cleavage so that it becomes the predominant pathway and occurs very fast to give an efficient deprotection reaction. The results reported here provide new insight into the photophysics, reaction pathways, and photochemistry of the p-hydoxyphenacyl acetate and related pHP caged phototrigger compounds and also provide a benchmark for further and more sophisticated investigations in the future. © 2006 American Chemical Society.
Persistent Identifierhttp://hdl.handle.net/10722/168070
ISSN
2015 Impact Factor: 2.883
2015 SCImago Journal Rankings: 1.231
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorChen, Xen_US
dc.contributor.authorMa, Cen_US
dc.contributor.authorKwok, WMen_US
dc.contributor.authorGuan, Xen_US
dc.contributor.authorDu, Yen_US
dc.contributor.authorPhillips, DLen_US
dc.date.accessioned2012-10-08T03:14:47Z-
dc.date.available2012-10-08T03:14:47Z-
dc.date.issued2006en_US
dc.identifier.citationJournal Of Physical Chemistry A, 2006, v. 110 n. 45, p. 12406-12413en_US
dc.identifier.issn1089-5639en_US
dc.identifier.urihttp://hdl.handle.net/10722/168070-
dc.description.abstractAb initio and density functional theory methods were employed to study the excited states and potential energy surfaces of the p-hydoxyphenacyl acetate (HPA) phototrigger compound. Complete active space (CAS) ab initio calculations predicted adiabatic electronic transition energies for the HPA-T 1( 3nπ*), HPA-T 2( 3ππ*), HPA-S 1( 1nπ*), HPA-T 3( 3nπ*), HPA-S 2( 1nπ*), HPA-S 3( 1ππ*) ← HPA-S 0 transitions that were similar to and in agreement with those found experimentally for closely related aromatic ketones such as p-hydroxyacetophenone and results from similar calculations for other related aromatic carbonyl systems. The α or β bond cleavage reactions from the S 1 excited state were both found to have relatively high barriers to reaction, and the S 1, T 1, and T 2 states are close in energy with the three S 1( 1nπ*), T 1( 3nπ*), and T 2( 3ππ*) surfaces intersecting at the same region. The calculations suggest that intersystem crossing (ISC) can occur very fast from the S 1 state to the nearby triplet states. This is consistent with results from ultrafast spectroscopy experiments that observe the S 1 state ISC occurs within about 1-2 ps to produce a triplet state for HPA and related pHP compounds. The α and β bond cleavage reactions for the T 1 state of HPA are both predicted to have fairly high barriers and compete with one another. However, this is not completely consistent with experiments that observe the photodeprotection reactions (e.g. the β bond cleavage) of HPA and some other pHP phototriggers in largely water containing solvents are predominant and occur very fast to release the leaving group. Comparison of the computational results with experimental results for HPA and related pHP compounds suggests that water molecules likely play an important part in changing the triplet state β bond cleavage so that it becomes the predominant pathway and occurs very fast to give an efficient deprotection reaction. The results reported here provide new insight into the photophysics, reaction pathways, and photochemistry of the p-hydoxyphenacyl acetate and related pHP caged phototrigger compounds and also provide a benchmark for further and more sophisticated investigations in the future. © 2006 American Chemical Society.en_US
dc.languageengen_US
dc.publisherAmerican Chemical Society. The Journal's web site is located at http://pubs.acs.org/jpcaen_US
dc.relation.ispartofJournal of Physical Chemistry Aen_US
dc.subject.meshAcetates - Chemistryen_US
dc.subject.meshAcetophenones - Chemistryen_US
dc.subject.meshModels, Chemicalen_US
dc.subject.meshPhosphoric Acid Esters - Chemistryen_US
dc.subject.meshPhotochemistryen_US
dc.subject.meshQuantum Theoryen_US
dc.titleA theoretical investigation of p-hydroxyphenacyl caged phototrigger compounds: An examination of the excited state photochemistry of p-hydroxyphenacyl acetateen_US
dc.typeArticleen_US
dc.identifier.emailMa, C:macs@hkucc.hku.hken_US
dc.identifier.emailPhillips, DL:phillips@hku.hken_US
dc.identifier.authorityMa, C=rp00758en_US
dc.identifier.authorityPhillips, DL=rp00770en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.doi10.1021/jp064490een_US
dc.identifier.pmid17091942-
dc.identifier.scopuseid_2-s2.0-33751215842en_US
dc.identifier.hkuros131825-
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-33751215842&selection=ref&src=s&origin=recordpageen_US
dc.identifier.volume110en_US
dc.identifier.issue45en_US
dc.identifier.spage12406en_US
dc.identifier.epage12413en_US
dc.identifier.isiWOS:000241893900008-
dc.publisher.placeUnited Statesen_US
dc.identifier.scopusauthoridChen, X=9279664000en_US
dc.identifier.scopusauthoridMa, C=7402924979en_US
dc.identifier.scopusauthoridKwok, WM=7103129332en_US
dc.identifier.scopusauthoridGuan, X=8313149700en_US
dc.identifier.scopusauthoridDu, Y=35310175500en_US
dc.identifier.scopusauthoridPhillips, DL=7404519365en_US

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