TD-DFT study of the for coumarins

Houari, Ymène; Jacquemin, Denis; Laurent, Adèle D.

doi:10.1016/j.cplett.2013.08.002

Cited by 19 publications

(17 citation statements)

References 46 publications

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“…The Born–Haber thermodynamic cycle method (Figure ) was used to calculate the equilibrium constants for the fluorescent and chemiluminescent states. This approach could predict relatively accurate excited‐state dissociation constants (p K *) of coumarins, naphthol, and cyanonaphthol . The definition of p K * is given by Equations (7)–:

true normalp K^{*} = Δ G_{aq}^{*} (/) 2.303 R T

true Δ G_{aq}^{*} = Δ G_{gas}^{*} + Δ Δ G_{sol}^{*}

true Δ Δ G_{sol}^{*} = Δ G_{s} ((), H^{+}) + Δ G_{normals}^{*} ((), A^{-}) - Δ G_{normals}^{*} ((), AH)

true Δ G_{gas}^{*} = G_{gas} ((), H^{+}) + Δ G_{gas}^{*} ((), A^{-}) - Δ G_{gas}^{*} ((), AH)

…”

Section: Methodsmentioning

confidence: 99%

“…This approach could predict relatively accurate excited-state dissociation constants (pK*) of coumarins, naphthol, and cyanonaphthol. [31,32] The definition of pK*i sg iven by Equations 7 The Gibbs energy in the gas phase was calculated by numerical vibrational frequency analysis at the TD wB97XD/6-31 + G(d) level of theory.Z ero-point effects were considered in the calculations. The solvation-free energy,i nt urn, was calculated at the solution-phase geometry as the difference in electronic energy in solution and that in the gas phase, using the PCM model with the UAKS radii where the computation of pK*a re usually performed with the UAKS radii.…”

Section: Calculations Of the Equilibrium Constants For The Fluorescenmentioning

confidence: 99%

“…At the same time, proton transfer is one of the most fundamental processes in chemistry and biology. Many experimental and theoretical research into the mechanism of excited‐state proton transfer reactions have been reported . The protonation/deprotonation reaction can be quantified by the excited‐state equilibrium constants (p K * ).…”

Section: Introductionmentioning

confidence: 99%

“…Many experimental and theoretical research into the mechanism of excited-state proton transfer reactions have been reported. [23][24][25][26][27][28][29][30][31][32] The proto-nation/deprotonation reactionc an be quantified by the excited-state equilibrium constants( p K * ). In this paper,t he computation of pK * was used to deduce the most probable form of the fluorescent and chemiluminescent emitters.…”

Section: Introductionmentioning

confidence: 99%

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A Computational Investigation of the Equilibrium Constants for the Fluorescent and Chemiluminescent States of Coelenteramide

Min

Silva

et al. 2016

ChemPhysChem

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In spite of recent advances in understanding the mechanism of coelenterate bioluminescence, there is no consensus about which coelenteramide specie and/or state are the light emitter. In this study, a systematic investigation of the geometries and spectra of all possible light emitters has been performed at the TD ωB97XD/6-31+G(d) level of theory, including various fluorescent and chemiluminescent states in vacuum, in a hydrophobic environment and in aqueous solution. To deduce the most probable form of the fluorescent and chemiluminescent coelenteramide emitter, the equilibrium constants for the fluorescent and chemiluminescent states connecting the various species have been calculated. ωB97XD gives a qualitatively good description of fluorescent and chemiluminescent structures. Coelenteramide is formed in a "dark" chemiluminescent state and must evolve to a bright fluorescent state. Moreover, the photoacidity of the phenol group is significantly higher in the fluorescent state than in the chemiluminescent state, which allows the formation of phenolate coelenteramide and clarifies its role as the bioluminescent emitter.

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true normalp K^{*} = Δ G_{aq}^{*} (/) 2.303 R T

true Δ G_{aq}^{*} = Δ G_{gas}^{*} + Δ Δ G_{sol}^{*}

true Δ Δ G_{sol}^{*} = Δ G_{s} ((), H^{+}) + Δ G_{normals}^{*} ((), A^{-}) - Δ G_{normals}^{*} ((), AH)

true Δ G_{gas}^{*} = G_{gas} ((), H^{+}) + Δ G_{gas}^{*} ((), A^{-}) - Δ G_{gas}^{*} ((), AH)

…”

Section: Methodsmentioning

confidence: 99%

Section: Calculations Of the Equilibrium Constants For The Fluorescenmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A Computational Investigation of the Equilibrium Constants for the Fluorescent and Chemiluminescent States of Coelenteramide

Min

Silva

et al. 2016

ChemPhysChem

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“…However, it is not uncommon for photoacids to exhibit excited‐state potential energy surfaces that are qualitatively different from their ground‐state counterparts. This may lead to poor agreement between the equilibrium constants predicted by the Förster equation and those derived in a more rigorous fashion by explicit computation of excited‐state free energies of a Born–Haber (BH) cycle …”

Section: Introductionmentioning

confidence: 99%

Distinguishing between keto-enol and acid-base forms of firefly oxyluciferin through calculation of excited-state equilibrium constants

Falklöf

Durbeej

2014

J. Comput. Chem.

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While recent years have seen much progress in the elucidation of the mechanisms underlying the bioluminescence of fireflies, there is to date no consensus on the precise contributions to the light emission from the different possible forms of the chemiexcited oxyluciferin (OxyLH2) cofactor. Here, this problem is investigated by the calculation of excited-state equilibrium constants in aqueous solution for keto-enol and acid-base reactions connecting six neutral, mono-anionic and di-anionic forms of OxyLH2.Particularly, rather than relying on the standard Förster equation and the associated assumption that entropic effects are negligible, these equilibrium constants are for the first time calculated in terms of excited-state free energies of a Born-Haber cycle.Performing quantum chemical calculations with density functional theory methods and using a hybrid cluster-continuum approach to describe solvent effects, a suitable protocol for the modeling is first defined from benchmark calculations on phenol. Applying this protocol to the various OxyLH2 species and verifying that available experimental data (absorption shifts and ground-state equilibrium constants) are accurately reproduced, it is then found that the phenolate-keto-OxyLH -mono-anion is intrinsically the preferred form of OxyLH2 in the excited state, which suggests a potential key role for this species in the bioluminescence of fireflies. Keywords Graphical Table of ContentsAqueous keto-enol and acid-base excited-state equilibrium constants between six neutral, mono-anionic and di-anionic forms of oxyluciferin, the cofactor responsible for the bioluminescence of firefly luciferase, are for the first time calculated from free energies of a Born-Haber cycle, rather than using the Förster equation. Thereby, it is found that the phenolate-keto-OxyLH -mono-anion is the preferred excited-state form of oxyluciferin in aqueous solution, attributing a potential key role to this species in the bioluminescence of fireflies.

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Performance of the COSMO solvation model for photoacidity and basicity in water

Ghiami-Shomami

Hättig

2023

J Comput Chem

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The possibilities and problems to predict excited‐state acidities and basicities in water with electronic structure calculations combined with a continuum solvation model are investigated for a test set of photoacids and photobases. Different error sources, like errors in the ground‐state pKa values, the excitation energies in solution for the neutral and (de‐)protonated species, basis set effects, and contributions beyond implicit solvation are investigated and their contributions to the total error in pKa∗ are discussed. Density functional theory in combination with the conductor like screening model for real solvents and an empirical linear Gibbs free energy relationship are used to predict the ground‐state pKa values. For the test set, this approach gives more accurate pKa values for the acids than for the bases. Time‐dependent density‐functional theory (TD‐DFT) and second‐order wave function methods in combination with the conductor like screening model are applied to compute excitation energies in water. Some TD‐DFT functionals fail for several species to predict correctly the order of the lowest excitations. Where experimental data for absorption maxima in water is available, the implicit solvation model leads with the applied electronic structure methods in most cases for the excitation energies in water to an overestimation for the protonated and to an underestimation for the deprotonated species. The magnitude and sign of the errors depend on the hydrogen bond donating and accepting ability of the solute. We find that for aqueous solution this results generally in an underestimation in the pKa changes from the ground to the excited state for photoacids and an overestimation for photobases.

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TD-DFT study of the for coumarins

Cited by 19 publications

References 46 publications

A Computational Investigation of the Equilibrium Constants for the Fluorescent and Chemiluminescent States of Coelenteramide

A Computational Investigation of the Equilibrium Constants for the Fluorescent and Chemiluminescent States of Coelenteramide

Distinguishing between keto-enol and acid-base forms of firefly oxyluciferin through calculation of excited-state equilibrium constants

Performance of the COSMO solvation model for photoacidity and basicity in water

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