A reatividade do estado excitado triplete de 1,3-indanodiona em benzeno

Santos, Frances R. dos; Silva, Mônica T. da; Netto‐Ferreira, José Carlos; Lucas, Nanci C. de

doi:10.1590/s0100-40422007000400025

Cited by 3 publications

(3 citation statements)

References 19 publications

(21 reference statements)

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“…The stabilizers were chosen such that the triplet energies of the additives were lower than the triplet energy of PyP, but higher than the 22 kcal mol )1 needed to generate 1 O 2 from ground state triplet oxygen. Even though PyP's exact triplet energy is not known, we believe that the value should be close to that of 1,3indandione which is reported to be ca 52 kcal mol )1 (40). The triplet energies of the chosen triplet sensitizers (perylene, COT and trans-stilbene) are 40, 45.8 and 49 kcal mol )1 , respectively (41).…”

Section: Resultsmentioning

confidence: 61%

Pyrophthalones as Blue Wavelength Absorbers in Thermoplastic Media

Natarajan

Burns

Takemori

et al. 2011

Photochem & Photobiology

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We have explored the utility of pyrophthalones as violet-blue light filtering dyes in polymer matrices for wavelengths below 450 nm. Further, we have investigated the photodegradation of these molecules in thermoplastic media and the mechanisms behind their degradation. Finally, a range of additives have been explored to improve the photostability of these molecules to achieve the desired performance.

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Section: Resultsmentioning

confidence: 61%

Pyrophthalones as Blue Wavelength Absorbers in Thermoplastic Media

Natarajan

Burns

Takemori

et al. 2011

Photochem & Photobiology

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“…The maximum chemical yield (93%, HPLC; 81%, isolated) was obtained at 85% conversion of 10 (10% of unreacted starting material was recovered). At higher conversions, the yield began to decrease because of secondary photoreactions, as has been observed in the photochemistry of other phenyl ketone derivatives. , …”

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confidence: 73%

Electronic-State Switching Strategy in the Photochemical Synthesis of Indanones from o-Methyl Phenacyl Epoxides

Štacko

Šolomek²,

Klán³

2011

Org. Lett.

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An electronic excited-state switching strategy has been utilized to control the selectivity of a key photochemical step in the total synthesis of indanorine. The excited-state character of 4,5-dimethoxy-2-methylphenacyl epoxide was changed from an unfavorable (3)π,π* state to a productive (3)n,π* state by a temporary structural modification, resulting in a relatively efficient and high-yielding formation of an indanone derivative. The corresponding structural modification was selected on the basis of quantum chemical calculations prior to the synthesis.

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“…20 O caráter triplete dos transientes mostrados nas Figuras 1 e 2 foi confirmado por estudos de supressão empregando-se β-caroteno (E T = 19,0 kcal mol -1 ; φ ces =0; λ max triplete = 520 nm). [28][29][30] Para ambos os transientes a constante de velocidade de supressão observada correspondeu à constante de velocidade de difusão, tendo sido observada nos dois casos a formação do triplete de β-caroteno, resultante de um processo de transferência de energia triplete-triplete.…”

Section: Resultsunclassified

Estudo da reatividade do estado excitado triplete de 1,4-diaza-9-fluorenonas frente a doadores de hidrogênio e de elétron

Takaizumi¹,

Santos²,

Silva³

et al. 2009

Quím. Nova

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Recebido em 20/8/08; aceito em 18/3/09; publicado na web em 10/8/09 THE REACTIVITY OF THE TRIPLET EXCITED STATE OF 1,4-DIAZA-9-FLUORENONES TOWARDS HYDROGEN AND ELECTRON DONORS. The effect of the introduction of nitrogen atoms upon the triplet excited state reactivity of 1,4-diaza-9-fluorenone (1) and 1,4-diaza-9-benz[b]fluorenone (2), in acetonitrile, was investigated employing the nanosecond laser flash photolysis technique. The intersystem crossing quantum yield (φ ces ) for 1 and 2 was determined using 9-fluorenone as a secondary standard (φ ces = 0.48, in acetonitrile) and for both diazafluorenones a value of φ ces = 0.28 was found. Quenching rate constants ranged from 8.17x10 4 L mol -1 s -1 (2-propanol) to 1.02x10 10 L mol -1 s -1 (DABCO) for 1,4-diaza-9-fluorenone and from 6.95x10 5 L mol -1 s -1 (2-propanol) to 5.94x10 9 L mol -1 s -1 (DABCO) for 1,4-diaza-9-benz[b]fluorenone, depending if the quenching process involves energy, hydrogen or electron transfer. A comparison between quenching rate constants for both diazaflurenones and the parent compound, i.e. 9-fluorenone, a ketone with lowest triple state of ππ* configuration, lead to the conclusion that the reactive triplet excited state for 1,4-diaza-9-fluorenone and 1,4-diaza-9-benz[b]fluorenone has ππ* configuration.Keywords: fluorenones; laser flash photolysis; triplet excited state. INTRODUÇÃOA fotofísica e a fotoquímica de piridil cetonas dependem tanto da posição do nitrogênio no anel quanto do solvente, com ambos os efeitos cooperando na determinação das propriedades do estado excitado destes compostos.1-5 A posição do nitrogênio afeta a densidade de carga do carbono da carbonila e dos átomos de carbono do anel e, assim, determina não somente a característica do estado excitado triplete n,π* da carbonila, mas também a possibilidade destas moléculas reagirem tanto no estado excitado singlete quanto no triplete. A alta reatividade observada em reações de abstração de hidrogênio para o triplete de diversas dipiridil cetonas, comparado a benzofenona, é consequência do efeito retirador de elétrons do átomo de nitrogênio.1-5 Este comportamento foi observado para outras piridilcetonas, como piridilfenilcetona e seus derivados contendo substituintes polares.Efeito semelhante pode ser observado quando se comparam as propriedades fotoquímicas de xantona e 1-aza-xantona. Xantona possui alta reatividade para o estado triplete n,π* somente em meio apolar, como em alcanos. Por outro lado, em meio polar, hidroxílico ou não, 6 ou em sistemas supramoleculares como micelas, ciclodextrinas ou zeólitas, 7 xantona possui estado triplete de energia mais baixa com caráter π,π*, o qual apresenta pouca tendência para abstrair hidrogênio. Em contraste, 1-aza-xantona apresenta estado excitado triplete com configuração n,π* tanto em solvente polar quanto apolar, com a sua reatividade frente à reação de abstração de hidrogênio superando a de benzofenona em cerca de uma ordem de grandeza. 8,9 Esta característica é provavelmente um reflexo da alta energia de excitação da 1-aza...

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A reatividade do estado excitado triplete de 1,3-indanodiona em benzeno

Cited by 3 publications

References 19 publications

Pyrophthalones as Blue Wavelength Absorbers in Thermoplastic Media

Pyrophthalones as Blue Wavelength Absorbers in Thermoplastic Media

Electronic-State Switching Strategy in the Photochemical Synthesis of Indanones from o-Methyl Phenacyl Epoxides

Estudo da reatividade do estado excitado triplete de 1,4-diaza-9-fluorenonas frente a doadores de hidrogênio e de elétron

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