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Novel laser-induced luminescence resulting from benzophenone/O-propylated p-tert-butylcalix[4]arene complexes: a diffuse reflectance study

2003-08-06Journal article Restricted access
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dc.contributor.authorFerreira, Luis F. Vieira
dc.contributor.authorFerreira, Margarida R. Vieira
dc.contributor.authorSilva, José P. da
dc.contributor.authorMachado, Isabel Ferreira
dc.contributor.authorOliveira, Anabela S.
dc.contributor.authorPrata, José V.
dc.date.accessioned2020-06-09T17:27:56Z
dc.date.available2020-06-09T17:27:56Z
dc.date.issued2003-08-06
dc.description.abstractLaser-induced room temperature luminescence of air-equilibrated benzophenone/O-propylated p-tert-butylcalix[4]arene solid powdered samples revealed the existence of a novel emission, in contrast with benzophenone/p-tertbutylcalix[4]arene complexes, where only benzophenone emits. This novel emission was identified as phosphorescence of 1-phenyl-1,2-propanedione, which is formed as the result of an hydrogen atom abstraction reaction of the triplet excited benzophenone from the propoxy substituents of the calixarene. Room temperature phosphorescence was obtained in air-equilibrated samples in all propylated hosts. The decay times of the benzophenone emission vary greatly with the degree of propylation, the shortest lifetimes being obtained in the tri- and tetrapropylated calixarenes. Triplet–triplet absorption of benzophenone was detected in all cases, and is the predominant absorption in the p-tert-butylcalix[4]arene case, where an endo-calix complex is formed. Benzophenone ketyl radical formation occurs with the O-propylated p-tert-butylcalix[4]arenes hosts, suggesting a different type of host/guest molecular arrangement. Diffuse reflectance laser flash photolysis and gas chromatography–mass spectrometry techniques provided complementary information, the former about transient species and the latter regarding the final products formed after light absorption. Product analysis and identification clearly show that the two main degradation photoproducts following laser excitation in the propylated substrates are 1-phenyl1,2-propanedione and 2-hydroxybenzophenone, although several other minor photodegradation products were identified. A detailed mechanistic analysis is proposed. While the solution photochemistry of benzophenone is dominated by the hydrogen abstraction reaction from suitable hydrogen donors, in these solid powdered samples, the α-cleavage reaction also plays an important role. This finding occurs even with one single laser pulse which lasts only a few nanoseconds, and is apparently related to the fact that scattered radiation exists, due to multiple internal reflections possibly trapping light within non-absorbing microcrystals in the sample, and is detected until at least 20 µs after the laser pulse. This could explain how photoproducts thus formed could also be excited with only one laser pulse.pt_PT
dc.description.versioninfo:eu-repo/semantics/publishedVersionpt_PT
dc.identifier.citationFERREIRA, Luís F. Vieira; [et al] – Novel laser-induced luminescence resulting from benzophenone/O-propylated p-tert-butylcalix[4]arene complexes. A diffuse reflectance study. Photochemical & Photobiological Sciences. ISSN 1474-905X. Vol. 2, N.º 10 (2003), pp. 1002-1010pt_PT
dc.identifier.doi10.1039/b306582pt_PT
dc.identifier.issn1474-905X
dc.identifier.urihttp://hdl.handle.net/10400.21/11813
dc.language.isoengpt_PT
dc.peerreviewedyespt_PT
dc.publisherRoyal Society of Chemistrypt_PT
dc.relationSFRH/BPD/36500/2000 - FCTpt_PT
dc.relationSFRH/BPD/15589/2001 - FCTpt_PT
dc.relation.publisherversionhttps://pubs.rsc.org/en/content/articlepdf/2003/pp/b306582kpt_PT
dc.subjectLaser-inducedpt_PT
dc.subjectLuminescencept_PT
dc.subjectPhosphorescencept_PT
dc.subjectCalixarenept_PT
dc.titleNovel laser-induced luminescence resulting from benzophenone/O-propylated p-tert-butylcalix[4]arene complexes: a diffuse reflectance studypt_PT
dc.typejournal article
dspace.entity.typePublication
oaire.citation.endPage1010pt_PT
oaire.citation.issue10pt_PT
oaire.citation.startPage1002pt_PT
oaire.citation.titlePhotochemical & Photobiological Sciences Photochemical and Photobiological Sciencespt_PT
oaire.citation.volume2pt_PT
person.familyNamePrata
person.givenNameJosé Virgílio
person.identifier191765
person.identifier.ciencia-idC11A-9130-8981
person.identifier.orcid0000-0002-9068-2847
person.identifier.ridB-7214-2008
person.identifier.scopus-author-id9276778400
rcaap.rightsclosedAccesspt_PT
rcaap.typearticlept_PT
relation.isAuthorOfPublication15e229f3-a619-4931-87eb-799091dc1601
relation.isAuthorOfPublication.latestForDiscovery15e229f3-a619-4931-87eb-799091dc1601

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