Proton Transfer and Acidity Constant in the Excited State of Naphthols by Dynamic Analyses*

Tsutsumi, Kinzo; Shizuka, Haruo

doi:10.1524/zpch.1980.122.2.129

Cited by 47 publications

(23 citation statements)

References 27 publications

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“…Notably, the Förster cycle calculation assumes that proton transfer from *ArOH to a solvent molecule is rapid, with the acid–base equilibrium established within the lifetime of the excited states. , Therefore, this method allows for an estimation of p K a * values only. , Using this method, the excited state p K a * values for the OH substituent of both 2-naphthol and 1a are ∼3.4 ± 0.4 (see Section 1, SI, for details). This is in reasonable agreement with the value for 2-naphthol (p K a * ∼ 2.8) calculated from fluorescence titration data . Hence, the CH 2 ON(H)SO 2 CF 3 substituent at the 2-position does not significantly affect the photoacidity of the naphtholic OH.…”

Section: Results and Discussionmentioning

confidence: 99%

Mechanistic Insights into Rapid Generation of Nitroxyl from a Photocaged N-Hydroxysulfonamide Incorporating the (6-Hydroxynaphthalen-2-yl)methyl Chromophore

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Zhou

et al. 2021

J. Org. Chem.

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HNO is a highly reactive molecule that shows promise in treating heart failure. Molecules that rapidly release HNO with precise spatial and temporal control are needed to investigate the biology of this signaling molecule. (Hydroxynaphthalen-2-yl)methylphotocaged N-hydroxysulfonamides are a new class of photoactive HNO generators. Recently, it was shown that a (6-hydroxynaphthalen-2-yl)methyl (6,2-HNM)-photocaged derivative of N-hydroxysulfonamide incorporating the trifluoromethanesulfonamidoxy group (1) quantitatively generates HNO. Mechanistic studies have now been carried out on this system and reveal that the ground state protonation state plays a key role in whether concerted heterolytic C−O/N−S bond cleavage to release HNO occurs versus undesired O−N bond cleavage. N-Deprotonation of 1 can be achieved by adding an aqueous buffer or a carboxylate salt to an aprotic solvent. Evidence is presented for C−O/N−S bond heterolysis occurring directly from the singlet excited state of the N-deprotonated parent molecule on the picosecond time scale, using femtosecond time-resolved transient absorption spectroscopy, to give a carbocation and 1 NO − . This is consistent with the observation of significant fluorescence quenching when HNO is generated. The carbocation intermediate reacts rapidly with nucleophiles including water, MeOH, or even (H)NO in the absence of a molecule that reacts rapidly with (H)NO to give an oxime.

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Section: Results and Discussionmentioning

confidence: 99%

Mechanistic Insights into Rapid Generation of Nitroxyl from a Photocaged N-Hydroxysulfonamide Incorporating the (6-Hydroxynaphthalen-2-yl)methyl Chromophore

Cink

Zhou

et al. 2021

J. Org. Chem.

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“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] In the case of 2-naphthol, the pKa decreases from 9.5 in the ground state to 2.8 in the excited state. 18 In acid solution, the emission is from naphthol, with an emission maximum of 357 nm ( Figure 18.1).…”

Section: L8la Excited-state Ionization Of Naphtholmentioning

confidence: 99%

Excited-State Reactions

Lakowicz

1999

Principles of Fluorescence Spectroscopy

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“…Secondly, the prototropic position in an excited molecule is important for proton-induced quenching (15). When the prototropic reaction takes place at the electrondonating substituent (amino or hydroxy group) of aromatic compounds, proton-induced quenching occurs effectively by electrophilic attack at one of the carbon atoms of the aromatic ring (13,15,(18)(19)(20). That is, effective proton-induced quenching is caused in the case that the electrophilic protonation occurs at a different ~osition from that of the Drototropic reaction.…”

Section: Triplet-triplet Absorbance Titration Curvementioning

confidence: 99%

“…arnines) and dynamic analyses taking into account the protoninduced quenching are, therefore, needed in order to obtain the correct pK,* values (1 7). The dynamic analyses by means of nanosecond time-resolved spectroscopy with fluorimetry were applied to the other aromatic amines (18-20) and naphthols (13). The Stuttgart group (21) has supported our method to determine the pK,* values of naphthylamines.…”

Section: Introductionmentioning

confidence: 99%

Acid–base properties in the triplet state of aromatic ketones studied by nanosecond laser flash photolysis

Shizuka¹,

Kimura²

1984

Can. J. Chem.

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Acid–base properties in the triplet state of aromatic ketones in H2O–CH3CN (4:1) mixtures have been studied by means of nanosecond laser flash photolysis. The acidity constants pKa(T) in the triplet state were determined by the Tn ← T1 absorbance titration curve, the Ware plot, and the Rayner–Wyatt plot. Good agreement among them shows that the acid–base equilibrium in the T1 state of aromatic ketones is established during the triplet lifetime. A linear relation between pKa(T) and the Taft σ* values was obtained for phenyl alkyl ketones.

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Proton Transfer and Acidity Constant in the Excited State of Naphthols by Dynamic Analyses*

Cited by 47 publications

References 27 publications

Mechanistic Insights into Rapid Generation of Nitroxyl from a Photocaged N-Hydroxysulfonamide Incorporating the (6-Hydroxynaphthalen-2-yl)methyl Chromophore

Mechanistic Insights into Rapid Generation of Nitroxyl from a Photocaged N-Hydroxysulfonamide Incorporating the (6-Hydroxynaphthalen-2-yl)methyl Chromophore

Excited-State Reactions

Acid–base properties in the triplet state of aromatic ketones studied by nanosecond laser flash photolysis

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