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Photoreduction of triplet thioxanthone derivative by azolium tetraphenylborate: a way to photogenerate N-heterocyclic carbenes

dc.rights.licenseopen
hal.structure.identifierInstitut de Science des Matériaux de Mulhouse [IS2M]
hal.structure.identifierUniversité de Strasbourg [UNISTRA]
dc.contributor.authorTRINH, Thi Kim Hoang
hal.structure.identifierInstitut de Science des Matériaux de Mulhouse [IS2M]
hal.structure.identifierUniversité de Strasbourg [UNISTRA]
dc.contributor.authorMORLET-SAVARY, Fabrice
hal.structure.identifierInstitut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier [ICGM ICMMM]
dc.contributor.authorPINAUD, Julien
hal.structure.identifierInstitut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier [ICGM ICMMM]
dc.contributor.authorLACROIX-DESMAZES, Patrick
hal.structure.identifierInstitut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier [ICGM ICMMM]
dc.contributor.authorREIBEL, Corine
hal.structure.identifierLaboratoire d'innovation moléculaire et applications [LIMA]
dc.contributor.authorJOYEUX, Cécile
hal.structure.identifierLaboratoire d'innovation moléculaire et applications [LIMA]
dc.contributor.authorLE NOUEN, Didier
hal.structure.identifierLaboratoire de Photophysique et Photochimie Supramoléculaires et Macromoléculaires [PPSM]
dc.contributor.authorMÉTIVIER, Rémi
hal.structure.identifierLaboratoire de Photophysique et Photochimie Supramoléculaires et Macromoléculaires [PPSM]
dc.contributor.authorBROSSEAU, Arnaud
hal.structure.identifierLaboratoire de Chimie des Polymères Organiques [LCPO]
hal.structure.identifierTeam 1 LCPO : Polymerization Catalyses & Engineering
dc.contributor.authorHÉROGUEZ, Valérie
hal.structure.identifierInstitut de Science des Matériaux de Mulhouse [IS2M]
hal.structure.identifierUniversité de Strasbourg [UNISTRA]
dc.contributor.authorCHEMTOB, Abraham
dc.date.accessioned2020
dc.date.available2020
dc.date.issued2019
dc.identifier.issn1463-9076
dc.identifier.urihttps://oskar-bordeaux.fr/handle/20.500.12278/19760
dc.description.abstractEnAlthough N-heterocyclic carbenes (NHCs) have brought profound changes in catalytic organic synthesis, their generation generally requires an inert atmosphere and harsh conditions. To overcome these limitations, an air-stable NHC photogenerator has been developed involving two mild components: 1,3-bis(mesityl)imidazolium tetraphenylborate (IMesH+BPh4−) and electronically excited isopropylthioxanthone (ITX). In this study, the photochemical mechanism is investigated via the accurate identification of the transient species and photoproducts. Electron transfer reaction between the excited triplet state of ITX and BPh4− is demonstrated as being the primary photochemical step. Nanosecond laser spectroscopy shows an efficient quenching and the formation of the expected ITX radical anion. The oxidized borane species is not observed, suggesting that this short-lived species could dissociate very rapidly to give the phenyl radical – successfully identified using electron paramagnetic resonance – and triphenylborane. As regards the final photoproducts, 1H and 13C NMR spectroscopies support the formation of the targeted NHC, 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes), suggesting the occurrence of a subsequent proton transfer reaction between ITX radical anion and imidazolium cation (IMesH+). Gas chromatography-mass spectrometry reveals three other products: biphenyl, isopropylthioxanthene and ITX. Their formation can be reconciled with a 2-step mechanism of photoinduced electron/proton transfer reactions. 11B NMR spectroscopy demonstrates that the main organoboron photoproduct is diphenylborinic acid formed by oxidation of BPh3. Due to its Lewis acidity, Ph2BOH can react with IMes to yield an NHC–boron adduct.
dc.description.sponsorshipCarbènes N-hétérocycliques photolatents pour la polymérisation par ouverture de cycle différée - ANR-16-CE07-0016
dc.language.isoen
dc.publisherRoyal Society of Chemistry
dc.title.enPhotoreduction of triplet thioxanthone derivative by azolium tetraphenylborate: a way to photogenerate N-heterocyclic carbenes
dc.typeArticle de revue
dc.identifier.doi10.1039/c9cp03098k
dc.subject.halChimie
bordeaux.journalPhysical Chemistry Chemical Physics
bordeaux.page17036-17046
bordeaux.volume21
bordeaux.hal.laboratoriesLaboratoire de Chimie des Polymères Organiques (LCPO) - UMR 5629*
bordeaux.issue31
bordeaux.institutionBordeaux INP
bordeaux.institutionUniversité de Bordeaux
bordeaux.peerReviewedoui
hal.identifierhal-02285796
hal.version1
hal.origin.linkhttps://hal.archives-ouvertes.fr//hal-02285796v1
bordeaux.COinSctx_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:journal&rft.jtitle=Physical%20Chemistry%20Chemical%20Physics&rft.date=2019&rft.volume=21&rft.issue=31&rft.spage=17036-17046&rft.epage=17036-17046&rft.eissn=1463-9076&rft.issn=1463-9076&rft.au=TRINH,%20Thi%20Kim%20Hoang&MORLET-SAVARY,%20Fabrice&PINAUD,%20Julien&LACROIX-DESMAZES,%20Patrick&REIBEL,%20Corine&rft.genre=article


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