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dc.contributor.authorSiskos, M. G.en
dc.contributor.authorZarkadis, A. K.en
dc.contributor.authorSteenken, S.en
dc.contributor.authorKarakostas, N.en
dc.contributor.authorGaras, S. K.en
dc.date.accessioned2015-11-24T16:44:47Z-
dc.date.available2015-11-24T16:44:47Z-
dc.identifier.issn0022-3263-
dc.identifier.urihttps://olympias.lib.uoi.gr/jspui/handle/123456789/8834-
dc.rightsDefault Licence-
dc.subjectbond-dissociation energiesen
dc.subjectcontact ion-pairsen
dc.subjectexcited diphenylmethyl radicalsen
dc.subjectphotoinduced electron-transferen
dc.subjectstable free-radicalsen
dc.subjectpicosecond dynamicsen
dc.subjectarylmethyl radicalsen
dc.subjectaqueous-solutionen
dc.subjecttriphenylmethyl radicalsen
dc.subjectbimolecular formationen
dc.titlePhotodissociation of N-(triphenylmethyl)anilines: A laser flash photolysis, ESR, and product analysis studyen
heal.typejournalArticle-
heal.type.enJournal articleen
heal.type.elΆρθρο Περιοδικούel
heal.identifier.primaryDoi 10.1021/Jo9719261-
heal.identifier.secondary<Go to ISI>://000073769600019-
heal.identifier.secondaryhttp://pubs.acs.org/doi/pdfplus/10.1021/jo9719261-
heal.languageen-
heal.accesscampus-
heal.recordProviderΠανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείαςel
heal.publicationDate1998-
heal.abstractN-(Triphenylmethyl)anilines (Ph3C-NHPh-R, R = H, o-Me, m-Me, p-Me, p-CPh3), upon photolysis with 248- and 308-nm laser light, as well as by lamp irradiation with 254-nm light in acetonitrile and hexane solutions, undergo exclusively C-N bond homolysis to give the triphenylmethyl radical in a monophotonic process. Product analysis gives as main products Ph3CH, 9-Ph-fluorene, and PhNH2. The quantum yields for the formation of Ph3C. are high (0.6-0.8, 248-nm excitation) and independent of the solvent. This effective homolytic dissociation results from the low electronegativity difference between the carbon and nitrogen atoms constituting the bond to be broken, the low bond dissociation enthalpy of the C-N bond, the high excitation energy of the local chromophore (aniline), and probably from a favorable alignment of the C-N bond in a plane perpendicular to the anilino chromophore (due to the large steric requirements of the trityl group), thus enabling an effective hyperconjugative interaction with it. The above dissociation competes effectively with heterolytic cleavage, which is the pathway dominating, e.g., in the photolysis of Ph3C-Cl in MeCN under the same conditions. At high pulse intensities the trityl radicals formed above are excited by a second photon leading to either electrocyclization to 4a,4b-dihydro-9-phenylfluorenyl radical (DHPF.), or photoionization to PhaC(+), the latter only in MeCN and only on 248-nm photolysis. A new intermediate (9-Ph-4aH-fluorene) on the way to the final product 9-Ph-fluorene is identified resulting from electrocyclization, supporting a mechanism proposed earlier. The optical measurements are supported by ESR studies (irradiation with 254-nm light).en
heal.publisherAmerican Chemical Societyen
heal.journalNameJournal of Organic Chemistryen
heal.journalTypepeer reviewed-
heal.fullTextAvailabilityTRUE-
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