Geminate recombination of proton transfer reactions: time-resolved fluorescence study of 1-naphthol-3,6-disulfonate

Masad, Asnat; Huppert, Dan

doi:10.1016/0009-2614(91)85141-i

Cited by 17 publications

(11 citation statements)

References 15 publications

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“…The kinetic scheme should then include a geminate recombination process , as the first reverse step in the excited state and, at pH ≤ 3.0, a diffusional reprotonation as the second reverse step. It is noteworthy that geminate recombination was shown to occur after deprotonation of the parent compound 1-naphthol-3,6-disulfonate (Chart ). The kinetic analysis should then require us to take into account the time-dependent diffusion equation .…”

Section: Resultsmentioning

confidence: 99%

“…It is noteworthy that geminate recombination was shown to occur after deprotonation of the parent compound 1-naphthol-3,6-disulfonate (Chart ). The kinetic analysis should then require us to take into account the time-dependent diffusion equation . This aspect will be the subject of a further investigation.…”

Section: Resultsmentioning

confidence: 99%

“…The kinetic analysis should then require us to take into account the time-dependent diffusion equation. 25 This aspect will be the subject of a further investigation.…”

Section: Chart 4 Schemementioning

confidence: 98%

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Photoinduced Proton and Charge Transfers in a Dihydroxynaphthalene Derivative: Chromotropic Acid

et al. 2001

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Chromotropic acid (4,5-dihydroxynaphthalene-2,7-disulfonic acid) is a chelating agent whose fluorogenic character has never been explained yet. The excited-state behavior of chromotropic acid itself has never been reported, despite its relationship with naphthols that are well-known photoacids. The present paper is accordingly devoted to a thorough investigation of chromotropic acid emission in aqueous solutions, which revealed its excited-state prototropic behavior in relation with the key role of the ground-state internal H-bond between the two -OH groups (displayed by the very different pKvalues, 5.4 and 15.6). Experiments were carried out in the whole acidity range (8 M HClO 4 to 10 M NaOH) using steady-state and time-resolved fluorimetry. In concentrated HClO 4 , competitive quenching processes occurred, due to HClO 4 itself and to water, respectively, but no photoinduced deprotonation was observed. The former quenching was confirmed by studying the emission of 2,6-naphthalenedisulfonic acid in the same media. Photoinduced deprotonation from the first -OH group was only observed in diluted acidic solutions ([HClO 4 ] e 1 M), within 500 ps, leading to an intermediate species IS*, which in turn leads to the monoprotonated form HCA 3-* within ≈230 ps. The structure of HCA 3-* is resonance stabilized by an internal charge transfer. The lifetime of HCA 3-* is 2.1 ns. The structure of IS* was tentatively proposed to be an ion pair between H + and the hydroxylate form of HCA 3-*. The pK* value of the first -OH group (≈1.8) was deduced from the rate constants. A moderate photoacidity (∆pK ≈ -3.6 pK units on excitation) is then displayed. Regarding the second -OH group, its photoinduced deprotonation was never observed, even in strongly basic solutions (1 M e [NaOH] e 10 M), which points out the outstanding stability of HCA 3-*. The lifetime of the fully deprotonated form (1.76 ns) could only be measured after direct excitation in 10 M NaOH.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Photoinduced Proton and Charge Transfers in a Dihydroxynaphthalene Derivative: Chromotropic Acid

et al. 2001

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“…The influence of water structure on the PTTS kinetics is most conspicuous in the investigation of proton transfer in mixed water/organic solvents. Protolytic photodissociation of various hydroxyaromatic compounds was studied in series of mixtures of water with alcohols [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] and other solvents. 14,19,20 In all cases PTTS rates were found to decrease with decreasing molar fraction of water in the mixture.…”

Section: Introductionmentioning

confidence: 99%

Photochemistry of “Super” Photoacids. 2. Excited-State Proton Transfer in Methanol/Water Mixtures

et al. 2000

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Excited-state proton transfer to solvent (PTTS) of 5-cyano-2-naphthol was investigated in methanol/water mixtures. We have found that the time-resolved fluorescence data fit the solution of the Debye−Smoluchowski equation for the reversible geminate recombination of ions over the whole range of methanol/water concentration ratios. The rate constants of the elementary protolytic photochemical processes and their isotope effects were determined by a simultaneous analysis of the time-resolved fluorescence of the photoacid and its conjugated anion. The competition between adiabatic protonation and quenching of the excited naphtholate anion by the geminate proton was observed to diminish sharply near pure methanol. The dissociation rate coefficient near pure methanol depends on a power of the water concentration, which appears to decrease from 2 (for “ordinary” photoacids) to below 1 for “super” photoacids.

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“…Proton transfer dynamics of photoacids to the solvent have thus, being reversible in nature, been modelled using the Debye-von Smoluchowski equation for diffusion-assisted reaction dynamics in a large body of experimental work on HPTS [84][85][86][87] and naphthols [88][89][90][91][92], with additional studies on the temperature dependence [93][94][95][96][97][98], and the pressure dependence [99][100][101], as well as the effects of special media such as reverse micelles [102] or chiral environments [103]. Moreover, results modelled with the Debye-von Smoluchowski approach have also been reported for proton acceptors triggered by optical excitation (photobases) [104,105], and for molecular compounds with both photoacid and photobase functionalities, such as 10-hydroxycamptothecin [106] and coumarin 4 [107].…”

Section: Proton Recombination and Acid-base Neutralizationmentioning

confidence: 99%

Bimolecular Proton Transfer in Solution

Nibbering

Pines

2006

Hydrogen‐Transfer Reactions

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Geminate recombination of proton transfer reactions: time-resolved fluorescence study of 1-naphthol-3,6-disulfonate

Cited by 17 publications

References 15 publications

Photoinduced Proton and Charge Transfers in a Dihydroxynaphthalene Derivative: Chromotropic Acid

Photoinduced Proton and Charge Transfers in a Dihydroxynaphthalene Derivative: Chromotropic Acid

Photochemistry of “Super” Photoacids. 2. Excited-State Proton Transfer in Methanol/Water Mixtures

Bimolecular Proton Transfer in Solution

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