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Article: Direct Spectroscopic Observation of Closed-Shell Singlet, Open-Shell Singlet, and Triplet p-Biphenylyloxenium Ion

TitleDirect Spectroscopic Observation of Closed-Shell Singlet, Open-Shell Singlet, and Triplet p-Biphenylyloxenium Ion
Authors
Issue Date2014
PublisherACS. The Journal's web site is located at http://pubs.acs.org/journals/jacsat/index.html
Citation
Journal of the American Chemical Society, 2014, v. 136, p. 12364-12370 How to Cite?
AbstractThe photophysics and photochemistry of p-biphenylyl hydroxylamine hydrochloride was studied using laser flash photolysis ranging from the femtosecond to the microsecond time scale. The singlet excited state of this photoprecursor is formed within 350 fs and partitions into three different transients that are assigned to the p-biphenyloxy radical, the open-shell singlet p-biphenylyloxenium ion and the triplet p-biphenylyloxenium ion, having lifetimes of 40 μs, 45 ps, and 1.6 ns, respectively, in CH3CN. The open-shell singlet p-biphenylyloxenium ion predominantly undergoes internal conversion to produce the closed-shell singlet p-biphenylyloxenium ion, which has a lifetime of 5-20 ns. The longer-lived radical is unambiguously assigned by nanosecond time-resolved resonance Raman (ns-TR3) spectroscopy, and the assignment of the short-lived singlet and triplet oxenium ion transient absorptions are supported by matching time-dependent density functional theory (TD-DFT) predictions of the absorptions of these species, as well as by product studies that implicate the intermediacy of charged electrophilic intermediates. Product studies from photolysis give p-biphenylol as the major product and a chloride adduct as the major product when NaCl is added as a trap. Thermolysis studies give p-biphenylol as a major product, as well as water, ammonium, and chloro adducts. These studies provide a rare direct look at a discrete oxenium ion intermediate and the first detection of open-shell singlet and triplet configurations of an oxenium ion, as well as providing an intriguing example of the importance of excited state dynamics in governing the electronic state population of reactive intermediates. Direct Spectroscopic Observation of Closed-Shell Singlet, Open-Shell Singlet, and Triplet p-Biphenylyloxenium Ion. Available from: http://www.researchgate.net/publication/264742316_Direct_Spectroscopic_Observation_of_Closed-Shell_Singlet_Open-Shell_Singlet_and_Triplet_p-Biphenylyloxenium_Ion [accessed Jul 2, 2015].
Persistent Identifierhttp://hdl.handle.net/10722/211709

 

DC FieldValueLanguage
dc.contributor.authorLi, M-
dc.contributor.authorHanway, PJ-
dc.contributor.authorAlbright, TR-
dc.contributor.authorWinter, AH-
dc.contributor.authorPhillips, DL-
dc.date.accessioned2015-07-21T02:08:36Z-
dc.date.available2015-07-21T02:08:36Z-
dc.date.issued2014-
dc.identifier.citationJournal of the American Chemical Society, 2014, v. 136, p. 12364-12370-
dc.identifier.urihttp://hdl.handle.net/10722/211709-
dc.description.abstractThe photophysics and photochemistry of p-biphenylyl hydroxylamine hydrochloride was studied using laser flash photolysis ranging from the femtosecond to the microsecond time scale. The singlet excited state of this photoprecursor is formed within 350 fs and partitions into three different transients that are assigned to the p-biphenyloxy radical, the open-shell singlet p-biphenylyloxenium ion and the triplet p-biphenylyloxenium ion, having lifetimes of 40 μs, 45 ps, and 1.6 ns, respectively, in CH3CN. The open-shell singlet p-biphenylyloxenium ion predominantly undergoes internal conversion to produce the closed-shell singlet p-biphenylyloxenium ion, which has a lifetime of 5-20 ns. The longer-lived radical is unambiguously assigned by nanosecond time-resolved resonance Raman (ns-TR3) spectroscopy, and the assignment of the short-lived singlet and triplet oxenium ion transient absorptions are supported by matching time-dependent density functional theory (TD-DFT) predictions of the absorptions of these species, as well as by product studies that implicate the intermediacy of charged electrophilic intermediates. Product studies from photolysis give p-biphenylol as the major product and a chloride adduct as the major product when NaCl is added as a trap. Thermolysis studies give p-biphenylol as a major product, as well as water, ammonium, and chloro adducts. These studies provide a rare direct look at a discrete oxenium ion intermediate and the first detection of open-shell singlet and triplet configurations of an oxenium ion, as well as providing an intriguing example of the importance of excited state dynamics in governing the electronic state population of reactive intermediates. Direct Spectroscopic Observation of Closed-Shell Singlet, Open-Shell Singlet, and Triplet p-Biphenylyloxenium Ion. Available from: http://www.researchgate.net/publication/264742316_Direct_Spectroscopic_Observation_of_Closed-Shell_Singlet_Open-Shell_Singlet_and_Triplet_p-Biphenylyloxenium_Ion [accessed Jul 2, 2015].-
dc.languageeng-
dc.publisherACS. 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.titleDirect Spectroscopic Observation of Closed-Shell Singlet, Open-Shell Singlet, and Triplet p-Biphenylyloxenium Ion-
dc.typeArticle-
dc.identifier.emailLi, M: mdli@hku.hk-
dc.identifier.emailPhillips, DL: phillips@hku.hk-
dc.identifier.authorityPhillips, DL=rp00770-
dc.identifier.doi10.1021/ja505447q-
dc.identifier.hkuros244757-
dc.identifier.volume136-
dc.identifier.spage12364-
dc.identifier.epage12370-
dc.publisher.placeUSA-

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