Laser investigation of some oxazole and oxadiazole derivatives

Fouassier, Jean‐Pierre; Lougnot, Daniel Joseph; Wieder, Fernand; Fauré, J.

doi:10.1016/0047-2670(77)87002-0

Cited by 28 publications

(19 citation statements)

References 22 publications

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“…Although PBT and PBO can potentially be very important commercial polymers, only a modest number of studies addressing the photophysical and photochemical properties of benzothiazole and benzoxazole have been reported. − It is well established that the benzoxazole group has a considerable chromophoric effect on the fluorescence of conjugated systems because it enhances the emission quantum yield via a decrease in the nonradiative decay rate constant . The chromophoric effect of the benzoxazole group has been used in industrial fluorescers such as optical brighteners, organic scintillators, and laser dyes. ,− The latter applications have shown that 2,6-diphenylbenzo[1,2- d ;4,5- d ‘]bisoxazole ( 1 ) exhibits high photostability in ethanol/dioxane solution …”

Section: Introductionmentioning

confidence: 99%

Synthesis and Photophysical Properties of Some Benzoxazole and Benzothiazole Compounds

et al. 1996

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Several benzoxazole and benzothiazole compounds have been prepared and their extended configurations characterized by optical absorption and emission spectroscopy. In general, solutions of these compounds fluoresce strongly and exhibit emission spectral profiles which mirror their respective excitation spectra. One exception to this correlation results from a chromophore with a nonplanar ground state configuration which disrupts the extended π-network, promoting a strong hypsochromic shift of the absorption spectrum. The absorption, excitation, and emission spectra of these compounds also show a strong vibronic progression of ∼1300 cm-1 in accordance with the energy of ring-stretching modes for aromatic frameworks. This excited state molecular distortion is consistent with the ππ* nature of the optical excitation. Also, the energy gap between excitation and emission 0−0 bands of these benzoxazole and benzothiazole compounds and their polymeric forms are strongly influenced by the minimum allowed intermolecular space. In dilute solutions or for structures with bulky substituents, only small energy differences are observed between excitation and fluorescence 0−0 bands. In contrast, solid state samples devoid of side groups exhibit significantly larger energetic displacements accompanied by a pronounced broadening of both excitation and emission spectral profiles. These results suggest that strong intermolecular π-stacking interactions occur for the planar benzoxazoles and benzothiazoles in the solid state. Excited state lifetime decay measurements for PBO model compounds in toluene are monoexponential with essentially identical lifetimes under evacuated and standard pressure conditions. In the solid state, PBO and PBT model compounds exhibit biexponential luminescence decay lifetimes which were also not significantly affected by the presence of O2. Fibers of PBO and PBT revealed three oxygen independent, but wavelength dependent emitting species. The presence of only one emitting species for these benzoxazole compounds in solution, compared with their multiexponential lifetime behavior in the solid state, further supports strong π-interactions between these molecules in the solid state. This molecular configuration permits benzoxazole and benzothiazole compounds to undergo photoinduced electron transfer in the solid state, which in the presence of oxygen leads to the generation of superoxide.

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Section: Introductionmentioning

confidence: 99%

Synthesis and Photophysical Properties of Some Benzoxazole and Benzothiazole Compounds

et al. 1996

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“…The photosensitizers used in this study as well as isoprene, and in parenthesis, their experimental triplet energies (kJ/mol, in red) and the calculated adiabatic triplet energies (kJ/mol, in blue) at (U)B3LYP-D3/6-311+G(d,p) level. 30,[63][64][65][66] The isoprene dimers formed were characterized by 1 H nuclear magnetic resonance (NMR) and gas chromatography-mass spectrometry (GCMS) analysis (Fig. S6 -S9, ESI †).…”

Section: Figmentioning

confidence: 99%

A Combined Photobiological-Photochemical Route to C10 Cycloalkane Jet Fuels from Carbon Dioxide via Isoprene

Rana¹,

Gomes²,

Rodrigues³

et al. 2022

Preprint

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The hemiterpene isoprene is a volatile C5 hydrocarbon with industrial applications. It is generated today from fossil resources, but can also be made in biological processes. We have utilized engineered photosynthetic cyanobacteria for direct, light-driven production of bio-isoprene from carbon dioxide, and show that isoprene in a subsequent photochemical step, using either near-UV or simulated or natural solar light, can be dimerized into limonene, paradiprene, and isomeric C10H16 hydrocarbons (monoterpenes) in high yields under photosensitized conditions (above 90% after 44 hours with near-UV and 61% with simulated solar light). The optimal sensitizer in our experiments is di(naphth-1-yl)methanone which we use with a loading of merely 0.1 mol%. It can also easily be recycled for subsequent photodimerization cycles. The isoprene dimers generated are a mixture of [2+2], [4+2] and [4+4] cycloadducts, and after hydrogenation this mixture is nearly ideal as a drop-in jet fuel. Importantly the photodimerization can be carried out at ambient conditions. However, the high content of hydrogenated [2+2] dimers in our isoprene dimer mix lowers the flash point below the threshold (38 °C), yet, these dimers can be converted thermally into [4+2] and [4+4] dimers. When hydrogenated these monoterpenoids fully satisfy the criteria for drop-in jet fuels with regard to energy density, flashpoint, kinematic viscosity, density, and freezing point. Life-cycle assessment results show a potential to produce the fuel in an environmentally sustainable way.

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“…Le spectre S*1 ~ S* du B.B.O. avait été mesuré par Fouassier et al [9] en utilisant un laser à colorant synchrone d'un laser à rubis à modes bloqués. Ces auteurs n'avaient pu obtenir que neuf points entre 20 000 et 13 000 çm-1 pour tracer le spectre.…”

Section: Rappel Du Principe De Fonctionnement -unclassified

“…7b). Avec une concentration en oxygène {O2} égale à 2 x 10-3 M/1 [13], on déduit pour ko2 une valeur de 5 x 109 S -1 .I/M parfaitement compatible avec la valeur des constantes d'extinction de ce type de composé [9].…”

Section: Rappel Du Principe De Fonctionnement -unclassified

Réalisation d'un spectromètre d'absorption « picoseconde » monofaisceau. Application à la dynamique des états excités des molécules organiques

Rullière¹,

Declémy²,

Pee³

1983

Rev. Phys. Appl. (Paris)

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2014 Un spectromètre d'absorption résolue en temps et entièrement automatisé a été construit. Il permet d'obtenir des spectres d'absorption et de gain d'états excités de durée de vie 03C4 > 10 ps. Ce spectromètre utilise une impulsion lumineuse d'une durée de 25 ps délivrée par un laser YAG/Nd3+ à modes bloqués. Le faisceau d'analyse est obtenu en focalisant cette impulsion dans une cellule contenant de l'eau lourde D2O (création d'un continuum). Nous avons déterminé des conditions expérimentales pour lesquelles la distribution spectrale de ce faisceau ne varie pas. Dans ces conditions, le même faisceau sert à la fois pour l'analyse et la référence et permet d'utiliser un détecteur monodimensionnel constitué par une barrette de photodiodes. On tire ainsi parti des avantages que présente ce type de détecteur (dynamique de réponse importante, robustesse, faible coût) par rapport aux tubes vidicon plus souvent utilisés. La densité optique minimale mesurable couramment avec notre système est de 0,03 et peut même atteindre la valeur de 0,01 moyennant quelques précautions. Le spectre d'absorption d'une espèce excitée à courte durée de vie dans la gamme spectrale 25 000-10 000 cm-1 est ainsi obtenu en quelques minutes. Quelques exemples d'application (mesure de durée de vie, spectre d'absorption, cinétiques de gain) sont présentés.Abstract. 2014 Picosecond absorption spectrometer has been built Mode locked YAG/Nd3+ laser is used both as an

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Laser investigation of some oxazole and oxadiazole derivatives

Cited by 28 publications

References 22 publications

Synthesis and Photophysical Properties of Some Benzoxazole and Benzothiazole Compounds

Synthesis and Photophysical Properties of Some Benzoxazole and Benzothiazole Compounds

A Combined Photobiological-Photochemical Route to C10 Cycloalkane Jet Fuels from Carbon Dioxide via Isoprene

Réalisation d'un spectromètre d'absorption « picoseconde » monofaisceau. Application à la dynamique des états excités des molécules organiques

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