Time-resolved fluorescence and absorption spectra and two-step laser excitation fluorescence of the excited-state proton transfer in the methanol solution of 7-hydroxyquinoline

Itoh, Michiya; Adachi, Takayuki; Tokumura, Kunihiro

doi:10.1021/ja00316a004

Cited by 108 publications

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“…The geometries are similar to those reported in previous studies. [8,16] The H-bond between O and O1 in the reactant seems to be stronger than the others in both the reactant and product. Judging from the donor-acceptor distances (2.8-2.9 Å for the oxygen-oxygen pairs and 2.9-3.0 Å for the nitrogen-oxygen pairs), all the H-bonds are medium rather than shortstrong in both the reactant and product.…”

Section: Methodsmentioning

confidence: 98%

“…Data for other isotopomers b Experimental value for isolated cluster in supersonic jet. [8] FIGURE 3 Distributions of population-weighted transmission probability, P(E), with respect to the energy relative to the E VAG of the reactant, E -E VAG reac , for the (A) HHH, (B) DHH, (C) HDH, and (D) DDD isotopomers at 298 K. The right end of the curve corresponds to the barrier top, at which E is equal to the maximum value of E VAG are shown in Figure S2. The plot is linear even for k SCT values, which include contribution from the tunneling.…”

Section: Rate Constants and Kinetic Isotope Effectsmentioning

confidence: 99%

“…Because of the high complexity of such systems, simple models have been extensively studied to understand the mechanism and dynamics of multiple PT in various environments at the molecular level. For example, 7-azaindole [1][2][3][4][5][6] and 7-hydroxyquinoline (7HQ) [7][8][9][10][11][12][13][14][15][16] have been investigated, both experimentally and theoretically, as biomimetic models. When excited by UV irradiation, these compounds are converted to their tautomers via multiple PT mediated by protic molecules such as H 2 O, alcohol, and NH 3 .…”

Section: Introductionmentioning

confidence: 99%

“…[7] Since then, the ESPT of 7HQ has been extensively studied in various environments such as supersonic jets, [8] alcohol solutions, [9][10][11] alcoholhydrocarbon mixed solutions, [9,10,12] and water nanopools in reverse micelles. [13] The precursor of alcohol-mediated ESPT is a cyclic H-bonded complex, 7HQ·(alcohol) 2 , in which one 7HQ and 2 alcohol molecules are connected by 3 H-bonds, as shown in Scheme 1.…”

Section: Introductionmentioning

confidence: 99%

“…Although 7HQ·(MeOH) 2 cluster has been observed with spectroscopic methods such as laser-induced fluorescence, hole-burning, and fluorescence-detected IR absorption in supersonic jets, [8] no ESPT occurs, and hence the tautomeric (ie, keto form) cluster cannot be generated in such cold-beam experiments. [8] Multiple PT reactions along cyclic H-bonds are interesting from the viewpoint of reaction mechanisms, and it has been often discussed whether a reaction is concerted or stepwise. In experimental studies, the primary KIE provides valuable information on the ratedetermining step.…”

Section: Introductionmentioning

confidence: 99%

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Reaction pathway and H/D kinetic isotope effects of the triple proton transfer in a 7‐hydroxyquinoline‐methanol complex in the ground state: A computational approach

Mori

2017

J of Physical Organic Chem

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Multiple proton transfer (PT) is an essential process in long-range proton transport such as proton relay in enzymes. 7-Hydroxyquinoline (7HQ) undergoes alcohol-mediated PT in both the excited and ground states, and this system has been investigated as a biomimetic model. In the present study, the reaction pathway of triple PT in a 7HQ-methanol cluster, 7HQ·(MeOH) 2 , in the ground state has been investigated using density functional theory calculations to clarify the reaction mechanism and the origin of the experimentally observed kinetic isotope effect (KIE). The PT takes place in an asynchronous concerted fashion, in which the oxygen atom in 7HQ first accepts a proton from the directly hydrogen-bonded MeOH. The rate constants and primary H/D KIEs have been estimated with canonical variational transition state theory in combination with the small curvature tunneling approximation. The tunneling effect on the PT rate is significant, and the KIE is much greater than 1 at room temperature. The rule of the geometric mean for the KIEs breaks down because of the asynchronicity in the motions of 3 protons and tunneling effect. In addition, the rate constant is smaller, the KIE is larger, and the activation energy is higher compared with the experimental values in heptane solution, suggesting that the PT dynamics in solution is governed by not only the intrinsic PT process but also thermal fluctuation of the solute and solvent molecules, which plays an important role in the configurational change of the 7HQ·(MeOH) 2 complex.

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Section: Methodsmentioning

confidence: 98%

Section: Rate Constants and Kinetic Isotope Effectsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Reaction pathway and H/D kinetic isotope effects of the triple proton transfer in a 7‐hydroxyquinoline‐methanol complex in the ground state: A computational approach

Mori

2017

J of Physical Organic Chem

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Controlling Excited‐State H‐Atom Transfer along Hydrogen‐Bonded Wires

Manca

Tanner

Leutwyler

2010

Hydrogen Bonding and Transfer in the Excited State

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Hydrogen-bonded wires are involved in a large variety of chemical and biological processes [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. The main reaction associated with hydrogen bonds is proton or H-atom transfer, in which a charge accompanies the transferring proton. A topic of specific interest is proton transport through transmembrane ion channels ('proton wires'), because many transmembrane proteins create, control and use the proton gradient across biological membranes. Hydrogen-bonded wires of water molecules have been identified in numerous membrane-spanning proteins, such as bacteriorhodopsin [17][18][19][20][21][22], the bacterial photosynthetic reaction centre of Rhodobacter sphaeroides [23], the transmembrane channel formed by gramicidin [24][25][26], cytochrome oxidase [27] and other voltage-gated proton channels [28]. The enzymes carbonic anhydrase [29,30] and alcohol dehydrogenase [30] also contain proton relays along chains of water molecules embedded in the interior of the protein. Recently, hydrogen-bonded ammonia wires have been detected in ammonia/ammonium transporter (Amt) transmembrane proteins, which are essential for nitrogen metabolism in all species [31,32]. The translocation mechanisms along these 'proton wires' have become fields of intense theoretical study [5-8, 24-26, 29, 30, 33, 34]. Most of the time, the assumed mechanism is Grotthuss type, after the inventor (1806) of the process. The modern version of the Grotthuss mechanism consists of successive transfers of an excess proton along a hydrogen-bonded wire. These transfers require sequences of reorientation of the wire molecules, which constitutes the rate-limiting step of the mechanism [35]. The excess proton diffuses through a hydrogen bond network via the formation/breaking of covalent bonds, as shown schematically in

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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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Time-resolved fluorescence and absorption spectra and two-step laser excitation fluorescence of the excited-state proton transfer in the methanol solution of 7-hydroxyquinoline

Cited by 108 publications

References 0 publications

Reaction pathway and H/D kinetic isotope effects of the triple proton transfer in a 7‐hydroxyquinoline‐methanol complex in the ground state: A computational approach

Reaction pathway and H/D kinetic isotope effects of the triple proton transfer in a 7‐hydroxyquinoline‐methanol complex in the ground state: A computational approach

Controlling Excited‐State H‐Atom Transfer along Hydrogen‐Bonded Wires

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

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