Electronic Absorption and Fluorescence Spectra of Indole . Derivatives. Quantitative Treatment of the Substituent Effects and a Theoretical Study

The room-temperature absorption spectra of nine substituted indoles containing the acetyl, bromo, carboxy, cyano, formyl, methoxy, methyl, and nitro substituents have been measured in cyclohexane, methanol, ethanol, ethanol-water (1 : 9, vol.), and in 0.1 .M NaOH ethanolic solution. The room-temperature excitation and emission fluo.rescence spectra of these compounds have been obtained in cyclohexane and ethanol. Satisfactory linear Hammett correlations have been established for the electronic absorption and fluorescence maxima wavenumbers of most of the indoles. PPP quantum-chemical calculations indicate a good agreement between the experimental and calculated electronic transitions and provide information about the distribution of Jt-electrons in the ground and the lowest excited singlet states of indole derivatives

Effect of electron donating substituents on the electronic absorption and fluorescence spectra of coumarin derivatives

Bull. Chem. Soc. Ethiop. 1996, 10(1), 33-38

Effect of electron donating substituents on the electronic absorption and fluorescence spectra of coumarin derivatives

Bull. Chem. Soc. Ethiop. 1996, 10(1), 33-38

The effect of pH on the electronic absorption, fluorescence and phosphorescence spectra of purines and pyrimidines. Determination of the lowest excited singlet and triplet state ionization constants

Room-temperature electronic absorption, fluorescence emission spectra, and low-temperature (77 K) phosphorescence spectra of sixteen purines and pyrimidines have been determined in aqueous solutions of different pH (range : — 7.6 — 14). Significant shifts of the long-wavelength absorption maxima and of the short-wavelength fluorescence maxima, respectively from 1,500 to 4,000 cm-1 and from 400 to 21,000 cm-1, occur upon protonation and deprotonation. pH-related shifts of the O-O band of phosphorescence range between 100 and 2,000 cm-1, according to the compound. Lowest excited singlet (pKSa) and triplet-state ionization constants (pKTa), have been calculated from these spectral shifts. pKSa and pKTa values are found to be significantly different from the corresponding ground-state pKa values, differences ranging respectively from 0.2 to 10 and from 0.2 to 4.5 log units. In the equilibria between cation and neutral species, the basicity of most of the purines and pyrimidines is increased in the excited singlet and triplet-state compared to the ground-state. In the equilibria between neutral and anion species, all purines and pyrimidines are more acidic in the excited singlet-state. The same behaviour is observed in the triplet-state, except for 6-mercaptopurine, uric acid, uracil and 5-fluorouracil which are significantly more basic, probably because of the increase of p-electron density at the NH group, in the triplet-state compared to the ground-state. The substituent effects upon the pKSa and pKTa are discussed

Direct Spectrofluorimetric Method for the Analysis of Carbofuran and Fluometuron in Senegalese Natural Waters

International audienc

Fluorescence quenching of two coumarin-3-carboxylic acids by trivalent lanthanide ions

International audienc

Solvolysis kinetic study and direct spectrofluorimetric analysis of the fungicide benomyl in natural waters

International audienceA direct spectrofluorimetric method for the quantitative analysis of benomyl in natural waters is described. Benomyl is an instable, fluorescent fungicide that mainly decomposes into carbendazim and n-butyl-isocyanate in organic and aqueous solutions. The kinetics of benomyl solvolysis reactions were investigated in organic solvents (methanol and acetonitrile) and in aqueous solvent systems, including β–cyclodextrin (β-CD), sodium dodecyl sulfate (SDS), dodecyltrimethylammonium chloride (DTAC), cetyltrimethylammonium chloride (CTAC), cetyltrimethylammonium hydroxide (CTAOH), Brij-700, Triton X-100 and water, at different pH and/or NaOH concentrations. The benomyl fluorescence signal was found to be quasi-completely stable in 10-2 M NaOH aqueous solution, various alkaline (10-2 M NaOH) organized media, β-CD neutral solution and Triton X-100 aqueous solutions of different pH. Based on these results, a direct spectrofluorimetric analytical method was developed for the determination of benomyl in 10-2 M NaOH aqueous solution and Triton X-100 solutions (pH7 and 10-2 M NaOH), with wide linear dynamic range (LDR) values of two to three orders of magnitude, very low limit of detection (LOD) and limit of quantification (LOQ) values of, respectively, 0.002-0.5 ng/mL and 0.007-2.0 ng/mL, and small relative standard deviation (RSD) values of 0.2-1.7 %, according to the medium. This direct spectrofluorimetric method was applied to the evaluation of benomyl residues in natural waters, with satisfactory recovery values (87-94%).</p

Determination of Agmatine Rate by Spectrofluorimetric Method in Alkaline Medium: Optimization and Application on Shrimp.

International audienc

Light effects on Carbofuran and Fluometuron: Impact on natural waters. Spectrophotometric study

International audienc