Mechanism and solvent dependence of the solvent-catalysed pseudo-intramolecular proton transfer of 7-hydroxyquinoline in the first electronically excited singlet state and in the ground state of its tautomer

Konijnenberg, Jan; Ekelmans, Gerben B.; Huizer, A. Herbert; Varma, Cyril A. G. O.

doi:10.1039/f29898500039

Cited by 90 publications

(172 citation statements)

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“…13,14 The excited-state proton-transfer reaction is a very fast process, and molecules experiencing this photoreaction may be switched in a picosecond time scale. 1e, 8,9 The advantages of such a device would be the high speed and selectivity of data transfer as the process is photocontrolled at a molecular level.…”

Section: Potential Perspectives Of 7hq In Molecular Assemblies Biolomentioning

confidence: 99%

Room-Temperature Proton Switching of 7-Hydroxyquinoline Dissolved in Rigid Hydroxylic and Carboxylic Polymeric Matrices

1996

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Room-temperature absorption and fluorescence spectra of 7-hydroxyquinoline in hydroxylic and carboxylic matrices show the coexistence of free, monobonded (bridged and unbridged), dibonded (bridged and unbridged), and keto forms of this dye in these media. In both matrices, the ground-state keto tautomer is stable. The bridged enol forms (λ em ) 380-400 nm) can undergo an excited-state (double or triple) proton-switching reaction, leading to the keto tautomer (λ em ) 500-520 nm) through an energy barrier. The reverse process does not occur upon excitation of the keto tautomer due to the greater stabilization (79 kJ mol -1 ) of this tautomer relative to that of the enol species in the excited state. Irradiation of the enol forms leads to stable keto tautomers in the ground state, and this opens the way for storing information at a molecular level.

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Section: Potential Perspectives Of 7hq In Molecular Assemblies Biolomentioning

confidence: 99%

Room-Temperature Proton Switching of 7-Hydroxyquinoline Dissolved in Rigid Hydroxylic and Carboxylic Polymeric Matrices

1996

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“…[8][9][10][11][12][13][14][15][16][17][18] Four prototropic species of 7-HQ are equilibrated in aqueous solution: a normal molecule (7-HQ(N)), an imine-protonated cation (7-HQ(C)), an enol-deprotonated anion (7-HQ(A)), and an enol-deprotonated imine-protonated tautomer (7-HQ(T)). 8 The pK a of the phenolic moiety of 7-HQ has been reported to be 9.0.…”

Section: Introductionmentioning

confidence: 99%

Resonance Raman Characterization of Different Forms of Ground-State 8-Bromo-7-hydroxyquinoline Caged Acetate in Aqueous Solutions

Nganga

et al. 2009

J. Phys. Chem. A

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The 8-bromo-7-hydroxyquinolinyl group (BHQ) is a derivative of 7-hydroxyquinoline (7-HQ) and BHQ molecules coexisting as different forms in aqueous solution. Absorption and resonance Raman spectroscopic methods were used to examine 8-bromo-7-hydroxyquinoline protected acetate (BHQ-OAc) in acetonitrile (MeCN), H(2)O/MeCN (60:40, v/v, pH 6 approximately 7), and NaOH-H(2)O/MeCN (60:40, v/v, pH 11 approximately 12) to obtain a better characterization of the forms of the ground-state species of BHQ-OAc in aqueous solutions and to examine their properties. The absorption spectra of BHQ-OAc in water show no absorption bands of the tautomeric species unlike the strong band at about 400 nm observed for the tautomeric form in 7-HQ aqueous solution. The resonance Raman spectra in conjunction with Raman spectra predicted from density functional theory (DFT) calculations reveal the observation of a double Raman band system characteristic of the neutral form (the nominal C=C ring stretching, C-N stretching, and O-H bending modes at 1564 and 1607 cm(-1)) and a single Raman band diagnostic of the enol-deprotonated anionic form (the nominal C=C ring, C-N, and C-O(-) stretching modes in the 1593 cm(-1) region). These results suggest that the neutral form of BHQ-OAc is the major species in neutral aqueous solution. There is a modest increase in the amount of the anionic form and a big decrease in the amount of the tautomeric form of the molecules for BHQ-OAc compared to 7-HQ in neutral aqueous solution. The presence of the 8-bromo group and/or competitive hydrogen bonding that hinder the formation and transfer process of a BHQ-OAc-water cyclic complex may be responsible for this large substituent effect.

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“…Besides 7AI , 7-hydroxyquinolines [68][69][70][71][72][73][74][75][76], b-carbolines [77][78][79][80][81] and pyrrole-containing heteroaromatics [82][83][84][85][86] are other prototypes where the ESPT tautomerism is mediated either by self-association or by adding guest molecules (including solvents) forming host/guest types of HB complex. From the structural viewpoint, the proton-donating and proton-accepting sites can be adjacent to each other, such that a complex possessing intact dual hydrogen bonds is formed through a perfectly fitted 1:1 (host:guest) stoichiometric ratio in the ground state.…”

Section: Catalytic Versus Non-catalytic Proton Transfermentioning

confidence: 99%

Excited‐State Proton Transfer via Hydrogen‐Bonded Dimers and Complexes in Condensed Phase

Hsieh

Jiang

Chou

2010

Hydrogen Bonding and Transfer in the Excited State

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Proton transfer represents one of the most fundamental processes involved in chemical reactions as well as in living systems [1]. Vast numbers of scientists have been participating in relevant research, leading to thousands upon thousands of publications and numerous books on the topic. Accordingly, various types of proton transfer reaction, depending on, for example, the reaction in the ground or excited state, adiabatic versus non-adiabatic, strong and weak hydrogen bonding, acidity (proton donor) and basicity (proton acceptor), have been identified [2][3][4][5][6][7][8]. At this time, proton transfer reactions seem to have the potential for unlimited extensions and aspects in terms of fundamentals and applications. Thus, to cover the broad spectrum of proton transfer research within a limited number of pages seems to be an unachievable task. Rather than trying to achieve the impossible, this chapter focuses mainly on areas related to excited-state proton transfer (ESPT) [9] with pre-existing intramolecular hydrogen bonds. Under this constraint, the photoinduced process involving excited-state proton dissociation and/or protonation in bulk solvents or clusters, also a currently active topic that has received considerable attention [10][11][12][13][14], unfortunately cannot be addressed in this chapter.One particular focus of this chapter is bifunctional molecules possessing a proton donor group and a proton acceptor group, such that ESPT takes place via self-associated hydrogen-bonded (HB) dimers and/or solvent bridge relay. In spite of numerous explorations and elegant research on guest-molecule-assisted ESPT reactions, the results of which have provided great insight into the fundamentals as well as perspectives in applications,

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Mechanism and solvent dependence of the solvent-catalysed pseudo-intramolecular proton transfer of 7-hydroxyquinoline in the first electronically excited singlet state and in the ground state of its tautomer

Cited by 90 publications

References 0 publications

Room-Temperature Proton Switching of 7-Hydroxyquinoline Dissolved in Rigid Hydroxylic and Carboxylic Polymeric Matrices

Room-Temperature Proton Switching of 7-Hydroxyquinoline Dissolved in Rigid Hydroxylic and Carboxylic Polymeric Matrices

Resonance Raman Characterization of Different Forms of Ground-State 8-Bromo-7-hydroxyquinoline Caged Acetate in Aqueous Solutions

Excited‐State Proton Transfer via Hydrogen‐Bonded Dimers and Complexes in Condensed Phase

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