Determination of rate constants of reaction and lifetimes of singlet oxygen in solution by a flash photolysis technique

Abstract

A flash photolysis technique, employing a dye-laser as the flash excitation source, was developed to determine, directly, the rate constant of decay (kd) of singlet oxygen (02' 8) and rate constant of reaction (ktx) between singlet oxygen and 1,3-diphenylisobenzofuran, DPBF, in a variety of solvents. Some results are the following: methanol, kd = (9.0 ± 0.6) X 101 *34 sec-1, k,x = (1.3 ± 0.1) X 109 sec-1 M-1, kdjk,x = 7.2 X 10-5 M; «-butyl alcohol, kd = (5.2 ± 0.8) X 104 sec-1, kIX = (0.80 ± 0.2) X Í09 sec-1 M-1, kdjk,x = 6.5 X 10-6 M; tertbutyl alcohol, kd = (3.0 ± 0.4) X 104sec-1, kTX = (0.57 ± 0.08) 109 sec-1 M-1, kdjktx = 5.3 X 10-6 M. Values in benzene: methanol (4:1), bromobenzene: methanol (4:1), pyridine, dioxane, methanol: water (1:1), methanol: glycol (1 :1), and glycol were also obtained. The resulting ß values (kdlkIX) are in good agreement with ß values determined in other ways. The technique was also shown useful for determination of absolute rate constants of reaction with or quenching of singlet oxygen by compounds such as 2,5-diphenylfuran and MV-dimethylaniline.

Singlet oxygen scavenging by leaf flavonoids contributes to sunlight acclimation in Tilia platyphyllos

“…Measurements were based on the leaf extract's ability to scavenge 1 O 2 and therefore prevent 32 the oxidation of 1,3-diphenylisobenzofuran (DPBF) dye (Young et al 1973 which is the natural environment of these leaves Y(II) decreased to nearly zero at the expense 5 of Y(NPQ) and all absorbed energy was dissipated (see upper row in Fig.1B). On the other 6 hand, when shade leaves were subjected to high PAR, Y(NPQ) pathways were not capable of 7 balancing the decrease in Y(II) and non regulated quenching increased (lower row in Fig.1B).…”

Palladium Complexes of Azomethine Derivatives of Porphyrins as Potential Photosensitizers

“…[23,24] 1,3-Diphenylisobenzofuran (DPIBF), the interaction of which with singlet oxygen takes place quantitatively with formation of colorless 1,2-dibenzoylbenzene product, was used as a chemical trap. [25] For the determination of quantum yields of singlet oxygen generation mixed solutions of the investigated compounds and DPIBF were prepared in a fixed volume of solvent. Measurements were performed in square quartz fluorescence cuvettes with optical path length 1 cm.…”

Fluorescein-Photosensitized Furan Oxidation in Methanolic and Reversed Micellar Solutions, Part I. Effects of Amines

“…DF has been used as effective scavenger for singlet oxygen in various oxidation reaction systems involving singlet oxygen by many workers [1][2][3][4]. DF oxidation reactions by singlet oxygen have been investigated in various homogeneous and micellar solutions [5][6][7], employing pyrene, thiazine dyes (methylene blue and thionine) and xanthene dyes (F, eosin Y, erythrosine B and rose bengal) as photosensitizer [2,3,[8][9][10].…”

“…DF oxidation reactions by singlet oxygen have been investigated in various homogeneous and micellar solutions [5][6][7], employing pyrene, thiazine dyes (methylene blue and thionine) and xanthene dyes (F, eosin Y, erythrosine B and rose bengal) as photosensitizer [2,3,[8][9][10].…”