Comparison of the rate of excited-state proton transfer from photoacids to alcohols and water

Simkovitch, Ron; Shomer, Shay; Gepshtein, Rinat; Roth, Michal E.; Shabat, Doron; Huppert, Dan

doi:10.1016/j.jphotochem.2013.12.009

Cited by 27 publications

(43 citation statements)

References 35 publications

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“…The strongest reported photoacid QCy9 even exceeds the boundaries of the correlation model with its remarkable proton transfer rate of~10 13 . [22,78] This is close to the stretching mode frequency of an OH-bond which is on the order of almost~10 14 s À 1 .…”

Section: Correlation Between Free-energy and Espt Ratessupporting

confidence: 68%

“…The highly conjugated dye QCy9 for example, exhibits a pK a * value as low as À 8.5 and is thus the strongest photoacid studied so far. [22] Following a mechanism different from ESPT, a protonrelease can also occur as a result of a photoreaction cascade which makes the respective compound a photoacid generator (PAG, Scheme 1B). [23] After activation, PAGs allow for a high increase in proton concentration, but often irreversibly.…”

Section: Introductionmentioning

confidence: 99%

“…The highly conjugated dye QCy9 for example, exhibits a pK a * value as low as −8.5 and is thus the strongest photoacid studied so far. [22] …”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Proton‐Transfer Dynamics of Photoacidic Merocyanines in Aqueous Solution

Kaiser

Halbritter

Heckel

et al. 2021

Chemistry A European J

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Photoacids attract increasing scientific attention, as they are valuable tools to spatiotemporally control protonrelease reactions and pH values of solutions. We present the first time-resolved spectroscopic study of the excited state and proton-release dynamics of prominent merocyanine representatives. Femtosecond transient absorption measurements of a pyridine merocyanine with two distinct protonation sites revealed dissimilar proton-release mechanisms: one site acts as a photoacid generator as its pK a value is modulated in the ground state after photoisomerization, while the other functions as an excited state photoacid which releases its proton within 1.1 ps. With a pK a drop of 8.7 units to À 5.5 upon excitation, the latter phenolic site is regarded a super-photoacid. The 6-nitro derivative exhibits only a phenolic site with similar, yet slightly less photoacidic characteristics and both compounds transfer their proton to methanol and ethanol. In contrast, for the related 6,8-dinitro compound an intramolecular proton transfer to the orthonitro group is suggested that is involved in a rapid relaxation into the ground state.

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Section: Correlation Between Free-energy and Espt Ratessupporting

confidence: 68%

Section: Introductionmentioning

confidence: 99%

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Proton‐Transfer Dynamics of Photoacidic Merocyanines in Aqueous Solution

Kaiser

Halbritter

Heckel

et al. 2021

Chemistry A European J

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“…Photoacids, the acidity of which can be controlled by light, have been intensively studied . The development of photoacids, including irreversible and reversible photoacids, has passed through three stages.…”

Section: Introductionmentioning

confidence: 99%

Effects of Substituents on Metastable‐State Photoacids: Design, Synthesis, and Evaluation of their Photochemical Properties

Liu

Tang

Sheng

et al. 2019

Chemistry An Asian Journal

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Recently,m etastable-state photoacids have been widely used to control protontransfer in numerousc hemical and biologicalp rocesses as well as applicationsw ith visible light. Generally,s ubstituents have ag reat influence on the photochemical properties of molecules, which will further affect their applications. Yet, the effects of substituents on metastable-state photoacids have not been studied systematically.I nt his work, 16 metastable-state photoacid derivatives were designeda nd synthesized on the basis of sub-stituents having al arge range of s-p electron-donor-acceptor capabilities. The effects of substituents on the color display [or maximuma bsorption band(s)], solubility,p K a values,d ark/photoacidity,p hotosensitivity,a nd relaxation kinetic(s) were investigated in detail.T his study will be helpful for the targeted design and synthesis of promisingp hotoacids and the application of their photocontrolled proton-release processes in functional materials/devices.Supporting Information and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

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“… 33 , 34 As a matter of fact, it exhibits a very large ESPT rate constant, k PT = 1 × 10 13 s –1 , the largest k PT value reported in the literature so far. 33 , 34 …”

Section: Introductionmentioning

confidence: 88%

Modeling Excited-State Proton Transfer to Solvent: A Dynamics Study of a Super Photoacid with a Hybrid Implicit/Explicit Solvent Model

Raucci¹,

Chiariello²,

Rega

2020

J. Chem. Theory Comput.

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The rapid growth of time-resolved spectroscopies and the theoretical advances in ab initio molecular dynamics (AIMD) pave the way to look at the real-time molecular motion following the electronic excitation. Here, we exploited the capabilities of AIMD combined with a hybrid implicit/explicit model of solvation to investigate the ultrafast excited-state proton transfer (ESPT) reaction of a super photoacid, known as QCy9, in water solution. QCy9 transfers a proton to a water solvent molecule within 100 fs upon the electronic excitation in aqueous solution, and it is the strongest photoacid reported in the literature so far. Because of the ultrafast kinetics, it has been experimentally hypothesized that the ESPT escapes the solvent dynamics control (Huppert et al., J. Photochem. Photobiol. A 2014, 277, 90). The sampling of the solvent configuration space on the ground electronic state is the first key step toward the simulation of the ESPT event. Therefore, several configurations in the Franck–Condon region, describing an average solvation, were chosen as starting points for the excited-state dynamics. In all cases, the excited-state evolution spontaneously leads to the proton transfer event, whose rate is strongly dependent on the hydrogen bond network around the proton acceptor solvent molecule. Our study revealed that the explicit representation at least of three solvation shells around the proton acceptor molecule is necessary to stabilize the excess proton. Furthermore, the analysis of the solvent molecule motions in proximity of the reaction site suggested that even in the case of the strongest photoacid, the ESPT is actually assisted by the solvation dynamics of the first and second solvation shells of the water accepting molecule.

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Comparison of the rate of excited-state proton transfer from photoacids to alcohols and water

Cited by 27 publications

References 35 publications

Proton‐Transfer Dynamics of Photoacidic Merocyanines in Aqueous Solution

Proton‐Transfer Dynamics of Photoacidic Merocyanines in Aqueous Solution

Effects of Substituents on Metastable‐State Photoacids: Design, Synthesis, and Evaluation of their Photochemical Properties

Modeling Excited-State Proton Transfer to Solvent: A Dynamics Study of a Super Photoacid with a Hybrid Implicit/Explicit Solvent Model

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