A laser flash photolysis study of the behaviour of polyfluorophenyl ketones in solution

Boate, D. R.; Johnston, Linda; Scaiano, J. C.

doi:10.1139/v89-142

Cited by 25 publications

(17 citation statements)

References 16 publications

(26 reference statements)

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“…[c] From Boate et al [38] ChemPhysChem 2010, 11, 2108 -2117 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim www.chemphyschem.org groups that could stabilize the incipient negative partial charge on the acceptor by delocalization are present in the compound. An opposite influence is observed when the electron-donating methoxy group is present.…”

Section: Quenching In Non-protic Solvents: Energetic Aspectsmentioning

confidence: 99%

“…[41] This even holds for the quenching of decafluorobenzophenone in ACN, despite the close to diffusion-controlled quenching rate constant. [38] 2.5. Quenching in Protic Solvents: Free Radical Ion Formation…”

mentioning

confidence: 99%

“…Filled symbols: this work; open symbol: literature data. [38] , namely the anisole cation radical and the BP radical anion. Instead, the transients are assigned as the anisole cation radical (l max = 430 nm) [42] and the BP ketyl radical (l max = 540 nm).…”

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confidence: 99%

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Efficient Photochemical Oxidation of Anisole in Protic Solvents: Electron Transfer driven by Specific Solvent–Solute Interactions

et al. 2010

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The dynamics of the bimolecular quenching of triplet excited benzophenone by anisole was studied by nanosecond flash photolysis. We carried out a detailed study of the solvent dependence of the reaction rates and efficiencies in a number of protic and non-protic solvents. These studies were augmented by theoretical modelling and experimental investigation of solute/solvent interactions in the triplet excited and the ground state, respectively. The triplet quenching that follows Stern-Volmer kinetics in all cases is profoundly dependent on the nature of the solvent, with the highest reactivity being consistently found in protic solvents. The results in non-protic solvents are compatible with unproductive quenching via a charge-transfer state, whereas the generally fast quenching in protic solvents is accompanied by efficient formation of free-radical products. Analysis of the solvent dependence in terms of Marcus theory reveals the impact of specific solvation of benzophenone by protic solvents on the ET driving force and kinetics. Specific solvation is found to support efficient free radical ion formation in media of moderate and low polarity as well.

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Section: Quenching In Non-protic Solvents: Energetic Aspectsmentioning

confidence: 99%

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confidence: 99%

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Efficient Photochemical Oxidation of Anisole in Protic Solvents: Electron Transfer driven by Specific Solvent–Solute Interactions

et al. 2010

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“…Contrariamente a 12, a alta instabilidade fotoquímica apresentada pelos compostos 10, 11 e 13, levando a produtos de polimerização e/ou decomposição, com a destruição completa de sua forma cristalina, possivelmente reflete a alta reatividade apresentada por compostos polifluorados, como demonstrado para a decafluorbenzofenona 30,31 .…”

Section: -Difluorchalcona (6); (B) 25-difluorchalcona (7); (C) 26-dunclassified

Fotoquímica de chalconas fluoradas no estado sólido

Cesarín-Sobrinho¹,

Netto‐Ferreira²

2002

Quím. Nova

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Recebido em 14/3/01; aceito em 20/6/01 PHOTOCHEMISTRY OF FLUORINATED CHALCONES IN THE SOLID STATE. Chalcone and its fluorinated derivatives were synthesized and photolyzed in the solid state. UV irradiation of chalcone and its monosubstituted fluorine derivatives (3-and 4-fluorchalcone) resulted in a mixture of anti-head-head (g-truxinic), sin-head-tail (a-truxilic) and anti-head-tail (e-truxilic) dimers. On the other hand, upon irradiation of 3,4-and 3,5-difluorchalcone a stereoselective formation of the a-truxilic photodimer was observed, whereas for 2-substituted chalcones (2,3-difluorchalcone, 2,5-difluorchalcone, 2,6-difluorchalcone and 2,3,4-trifluorchalcone) the b-truxilic dimer was stereoselectively obtained. 2',3',4',5',6'-pentafluorchalcone was the less reactive of all chalcones studied and at least one of the possible photodimers, i.e the anti-head-head isomer, was identified. Irradiation of polyfluorinated chalcones such as 2, 3,5,6-tetrafluor-, 2,3,4,5,6-pentafluor-, and 2,2',3,3',4,4',5,5',6,6'-decafluorchalcone led only to polymerization and/or decomposition products.Keywords: chalcone; photodimerization; solid state. INTRODUÇÃOAs fotorreações no estado cristalino têm sido estudadas desde o final do século XIX e vários trabalhos de revisão podem ser encontrados sobre o assunto 1,2 . Os trabalhos pioneiros nessa área tiveram início com Liebermann, em 1889, que estudou a dimerização de olefinas no estado cristalino 3,4 . Durante a primeira parte do século XX, vários pesquisadores iniciaram a sistematização dos resultados da dimerização no estado cristalino a partir do estudo da fotoquímica de ácido cinâmico e derivados. Somente após os anos 60, com o aparecimento de técnicas de difração de raios-X, foi possível a Schmidt e colaboradores avançarem no entendimento dos processos de fotodimerização no estado cristalino, para os quais foram estabelcidas regras importantes, denominadas de regras topológicas [5][6][7][8] . De acordo com os princípios topoquímicos, as reações no estado sólido se processam com um mínimo de movimento atômico, o que implica que só serão esperadas reações de dimerização em compostos apresentando ligações olefínicas se as ligações duplas estiverem paralelas e orientadas de forma correta sob o ponto de vista estereoquímico.Algumas reações no estado sólido aparentemente não seguem as regras topológicas e procedem ou através de defeitos ou em superfí-cies ou sítios onde o empacotamento cristalino é desordenado [9][10][11] . Mais recentemente, e visando um melhor entendimento das fotorreações no estado cristalino, foi introduzido o conceito de cavidade reacional 12 , que representa qualitativamente o espaço ocupado pelo reagente. Assim, os movimentos atômicos que se seguem durante uma determinada reação exercem pressão sobre as paredes da cavidade, a qual torna-se distorcida, limitando tanto os movimentos de deslocamento molecular quanto as mudanças conformacionais que são permitidas durante a reação 12 . A nível molecular, tem sido mostrado que as reações no estado sólido somente p...

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“…The DFBP triplet state is known to undergo hydrogen abstraction much more rapidly than BP [7][8][9]. Thus, one expects that DFBP can effectively abstract a hydrogen atom from DMSO and produce predominantly 'CH2SOCH3 .…”

Section: Confirmation Of Reaction Scheme Via Photochemical Reactions mentioning

confidence: 99%

Application of benzophenones to elucidate the photochemical reaction pathways of hydrogen peroxide with dimethylsulfoxide

et al. 2000

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Benzophenone ((C 6 H5),CO) and decafluorobenzophenone ((C 6Fs ) 2 CO) were applied to elucidate the photochemical reaction pathway of hydrogen peroxide (H,0 2) with dimethylsulfoxide (DMSO). When a solution of benzophenone in DMSO was excited with the 355 nm laser light, three transient species were observed in the time-resolved electron paramagnetic resonance spectra: benzophenone ketyl (C6H5)2COH', methyl 'CH 3 , and methylsulfinic methyl 'CH2SOCH3 radicals. However, when decafluorobenzophenone was used with DMSO, only ketyl and methylsulfinic methyl radicals were observed under the same experimental conditions. When the reaction of benzophenone and DMSO was carried out in the presence of H 2 02, different time profiles of 'CH 3 radicals were observed. In the reaction of decafluorobenzophenone-DMSO-H 20 2, the time profiles of the radicals were not affected by the presence of H 2 0,. Thus, these results verify that 'CH 3 radicals are regenerated in a cyclic pathway, in which 'CH, radicals attack H202 . The regeneration pathway allows us to observe f-pair polarization throughout the lifetime of 'CH 3 radicals, which last several microseconds, an order of magnitude longer than the T, relaxation time of 'CH3 radicals.

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A laser flash photolysis study of the behaviour of polyfluorophenyl ketones in solution

Cited by 25 publications

References 16 publications

Efficient Photochemical Oxidation of Anisole in Protic Solvents: Electron Transfer driven by Specific Solvent–Solute Interactions

Efficient Photochemical Oxidation of Anisole in Protic Solvents: Electron Transfer driven by Specific Solvent–Solute Interactions

Fotoquímica de chalconas fluoradas no estado sólido

Application of benzophenones to elucidate the photochemical reaction pathways of hydrogen peroxide with dimethylsulfoxide

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