• Guy Duportail

      Articles written in Journal of Chemical Sciences

    • The spectra, lifetime and laser activity of 2,5-bis-2(l-naphthyl) vinylpyrazine and 2,5-bis-2(2-naphthyl)vinylpyrazine

      Samy A El-Daly El-Zeiny M Ebeid Sadiq M El-Hazmy Abdallah S Babaqi Zenat El-Gohary Guy Duportail

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      Both 2,5-bis-2(l-naphthyl) vinylpyrazine (BNVP) and 2,5-bis-2(2-naphthyl) vinylpyrazine (B2NVP) diolefinic dyes have relatively short excited-state lifetimes, high fluorescence efficiencies and low photochemical quantum yields. BNVP solutions in dimethyl formamide and methylene chloride give amplified spontaneous emission (ASE) with a maximum at 500 nm. The low solubility of B2NVP in organic solvents does not allow the measurement of ASE for this dye. The excited state absorption spectra (ESA) of BNVP show an absorption band around 525 nm which reduces dye laser efficiency.

      Energy transfer from 7-diethylamino-4-methylcoumarin to BNVP and B2NVP has been studied by applying Stern-Volmer plots. The underlying mechanism is a radiative long range energy transfer.

      Both BNVP and B2NVP undergo solubilization in anionic as well as cationic micelles.

    • Effects of polar protic solvents on dual emissions of 3-hydroxychromones

      Andrey S Klymchenko Cyril Kenfack Guy Duportail Yves Mély

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      3-Hydroxychromones (3HC), exhibit dual emissions highly sensitive to solvent properties due to excited state intramolecular proton transfer (ESIPT). Therefore, 3HCs find wide applications as fluorescence probes in biological systems. Here, it is particularly important to understand the fluorescence behaviour of 3HCs in polar environments. Herein, we studied 3-hydroxyflavone, 2-(2-furyl)-3-hydroxychromone and 2-(2-benzofuryl)-3-hydroxychromone in high polarity solvents characterized by different H-bond donor abilities, donor concentrations and acceptor abilities. Our results show that the dual emissions of the dyes are insensitive to solvent basicity but strongly depend on the two other parameters. Moreover, furyl- and benzofuryl-substituted dyes were significantly more sensitive than the 3-hydroxyflavone to H-bond donor ability, while all three dyes showed roughly equivalent high sensitivity to H-bond donor concentration. These results can be explained by different mechanisms. Thus, the sensitivity of all three dyes to increasing concentrations of H-bond donors probably results from increase in the population of solvated dye with disrupted intramolecular H-bonds. Meantime, the sensitivity to Hbond donor ability of the solvent, observed mainly with furyl and benzofuryl dyes, is probably related to the strength of the H-bonds between the solvent and the 4-carbonyl group of the dye with intact intramolecular H-bonds. The present results provide new insights for further applications of 3HC derivatives as environment-sensitive probes and labels of biological molecules.

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