Monosubstituted naphthalenes as quenchers and generators of singlet molecular oxygen

Soltermann, Arnaldo T.; Luiz, Marta; Biasutti, M. Alicia; Carrascoso, María Luisa; Amat‐Guerri, F.; Garcı́a, Norman A.

doi:10.1016/s1010-6030(99)00172-0

Cited by 22 publications

(32 citation statements)

References 31 publications

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“…The behaviors observed in homogeneous media are coincident with those reported for bimolecular reaction between O 2 ( 1 △ g ) with several compounds including phenols and indoles (like Tyr and Trp) . All reactions have being explained through a mechanism involving an excited encounter complex [O 2 ( 1 △ g ) δ‐ … compound δ+ ] with partial charge‐transfer character.…”

Section: Resultssupporting

confidence: 80%

“…The observed photo‐stability of BSA can be attributed to the fact that the exited encounter complex with partial charge‐transfer character between the reactive species, O 2 ( 1 △ g ), and substrates like Tyr and Trp, is affected by the polarity of the micro‐environment. The respective value of k t decreases as the solvent polarity decreases . It is known that the macroscopic dielectric constant in the interior of the water pool in RMs is lower than that of free water and increases with the increase of the W value for the same micellar system .…”

Section: Resultsmentioning

confidence: 95%

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Influence of pH and micellar systems on the sensitized photo‐oxidation of bovine serum albumin

et al. 2019

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Photosensitized oxidation of bovine serum albumin (BSA), by using perinaphtenone as a sensitizer, has been studied at pH 7.4 and 11. The selected sensitizer does not present ground‐state complexation with BSA and ensures that the mechanism is mediated by O2(1△g). Strong dependence between BSA–O2(1△g) photo‐oxidation and the pH of the medium has been found. The relative oxygen uptake rate (v− △ O2) and the total quenching rate constant (kt) values are higher at pH 11 than pH 7.4. The enhancement in the alkaline condition is due to conformational changes in the protein and the reactivity of tyrosinate anion with O2(1△g). Even when the tendency with the pH in the presence of sodium dodecyl sulfate (SDS) micelles is similar to that observed in homogeneous media, an increment on the kt value is detected. This effect may be attributable to the strong interaction of BSA–SDS, which leads to the protein unfolding and could leave more exposed photo‐oxidizable amino acids. A protective effect against the O2(1△g)‐mediated photo‐oxidation was observed in reverse micelles (RMs) of sodium bis(2‐ethylhexyl)sulfosuccinate (AOT) by comparing the kt values obtained at W = 10 with respect to the one obtain in homogeneous media. The latter could be mainly explained by the modification in the solvent polarity. Also, another important observation was found, the internal pH inside RMs of AOT sensed through tyrosine absorption was independent of the one used for the formation of the water pool. Hence, the kt values observed at both pH, are quite similar.

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Section: Resultssupporting

confidence: 80%

Section: Resultsmentioning

confidence: 95%

Influence of pH and micellar systems on the sensitized photo‐oxidation of bovine serum albumin

et al. 2019

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“…In a previous study, 18 we have observed that 1-OHN and 2-OHN were reactive towards O 2 ( 1 ∆ g ) only in their respective naphthoate forms which is a common behaviour also shown by others hydroxyaromatic derivatives such as phenols, polyhydroxybenzenes and hydroxyanthraquinones. [19][20][21][22] For this reason, the present study was developed employing exclusively alkaline media.…”

Section: Resultsmentioning

confidence: 63%

Effect of reverse micelles on the Rose Bengal-sensitized photo-oxidation of 1- and 2-hydroxynaphthalenes

2004

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Benzylhexadecyl dimethylammonium chloride (BHDC) and sodium bis(2-ethylhexyl) sulfosuccinate (AOT) water-in-oil micro-emulsions were employed to study the influence of medium heterogeneity on singlet molecular oxygen [O(2)((1)Delta(g))]-mediated degradation of 1-hydroxynaphthalene (1-OHN) and 2-hydroxynaphthalene (2-OHN) in their naphthoate form. The kinetic study in the micellar system, that was considered as a closer model for the environment of contaminants in natural polluted waters, consisted of a comparative work with the process in homogeneous solution, by varying surfactant structure and water content of the micro-emulsion. While it is known that 1-OHN and 2-OHN are rapidly and efficiently photo-oxidised in aqueous medium, time-resolved phosphorescence detection of O(2)((1)Delta(g)) and stationary photolysis experiments demonstrate that both the values for the overall and reactive rate constants for the quenching of O(2)((1)Delta(g)) and the photo-oxidation efficiencies are lowered in BHDC micelles, whereas the photo-oxidative process in AOT micro-emulsions was totally inhibited. Results are interpreted and discussed on the basis of different locations of the probe in the micellar environment.

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“…Previous studies on naphthalene derivatives demonstrate that this type of compounds is able to generate singlet oxygen, 1 O 2 ( 1 g ), with relatively good yields [55][56][57][58]. We have used time resolved phosphorescence with emission monitored at 1270 nm to determine the singlet oxygen formation quantum yields (˚ ).…”

Section: Singlet Oxygen Measurementsmentioning

confidence: 99%

Photophysical characterization of the plant growth regulator 2-(1-naphthyl) acetamide

Silva

Wong-Wah-Chung

Sarakha

2013

Journal of Photochemistry and Photobiology A: Chemistry

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a b s t r a c tThe photophysical properties of the widely used plant growth regulator 2-(1-naphthyl) acetamide (NAD) were studied in water and representative organic solvents (ethanol, ethylene glycol, acetonitrile, chloroform, 1,4-dioxane) employing steady-state and time-resolved spectroscopy. Quantum yields and lifetimes of fluorescence, phosphorescence and triplet formation and triplet-triplet absorption spectra were obtained. From these, all radiative and radiationless rate constants have been determined, together with singlet and triplet excited state energies (4.00 and 2.69 eV, respectively). The fluorescence quantum yield and lifetime increased on going from water (˚F 0.066, F 35.0 ns) to non-hydrogen bonding solvents (˚F 0.357, F 51.0 ns in 1,4-dioxane), probably due to decreased internal conversion. Fluorescence was quenched by several anions through an electron transfer process. A limit on the reduction potential of 1 NAD* of E 0 2.1 ± 0.2 V was estimated. The attribution of the transient absorption seen in nanosecond laser flash photolysis to 3 NAD* was confirmed by energy transfer and oxygen quenching. Quenching of triplet states leads to singlet oxygen formation, with quantum yields varying from 0.097 in water to 0.396 in chloroform. However, these are lower than the triplet state quantum yields, particularly in water (˚T 0.424), indicating competing quenching pathways, probably involving electron transfer. The relevance of these results to the photoreactivity of NAD under environmental conditions is discussed.

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Monosubstituted naphthalenes as quenchers and generators of singlet molecular oxygen

Cited by 22 publications

References 31 publications

Influence of pH and micellar systems on the sensitized photo‐oxidation of bovine serum albumin

Influence of pH and micellar systems on the sensitized photo‐oxidation of bovine serum albumin

Effect of reverse micelles on the Rose Bengal-sensitized photo-oxidation of 1- and 2-hydroxynaphthalenes

Photophysical characterization of the plant growth regulator 2-(1-naphthyl) acetamide

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