Excited-State Intramolecular Proton Transfer Reaction of 3-Hydroxyflavone

Jiang, Yanxue; Peng, Yajing

doi:10.1007/s10876-015-0893-7

Cited by 18 publications

(8 citation statements)

References 53 publications

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“…All orbitals except HOMO-3 have the π characteristic; only HOMO-3 has an in-plane lone pair contribution from the carbonyl oxygen. In the bright S 1 (HOMO–LUMO) excitation, electron density is transferred from the OH-1 group in HOMO to the O atom in LUMO, making the proton more acidic and the O atom (the proton acceptor) more basic. ,, By this electron rearrangement, the ESIPT is facilitated. The S 2 state is characterized as having the n π* characteristic.…”

Section: Results and Discussionmentioning

confidence: 99%

Molecular Dynamics Simulation of the Excited-State Proton Transfer Mechanism in 3-Hydroxyflavone Using Explicit Hydration Models

Siddique

Aquino

et al. 2021

J. Phys. Chem. A

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3-Hydroxyflavon (3-HF) represents an interesting paradigmatic compound to study excited-state intramolecular proton transfer (ESIPT) and intermolecular (ESInterPT) processes to explain the experimentally observed dual fluorescence in solvents containing protic contamination (water) as opposed to single fluorescence in highly purified nonpolar solvents. In this work, adiabatic on-the-fly molecular dynamics simulations have been performed for isolated 3-HF in an aqueous solution using a polarizable continuum model and including explicit water molecules to represent adequately hydrogen bonding. For the calculation of the excited state, time-dependent density functional theory and the Becke-3-Lee-Yang-Parr (B3LYP) functional have been used. For the isolated 3-HF, ultrafast ESIPT from the enol group to the neighboring keto group has been observed. The calculated PT time of 48 fs agrees well with the experimental value of 39 fs. Addition of one water molecule quenches this ESIPT process but shows an intermolecular concerted or stepwise tautomerization process via the bridging water molecule. Adding a second or more water molecules inhibits this ESInterPT process to a large degree. Most of the trajectories do not show any PT, preserving the initial excited-state enol structure, which is the origin of the violet-blue fluorescence appearing in the solvents contaminated with protic components.

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Section: Results and Discussionmentioning

confidence: 99%

Molecular Dynamics Simulation of the Excited-State Proton Transfer Mechanism in 3-Hydroxyflavone Using Explicit Hydration Models

Siddique

Aquino

et al. 2021

J. Phys. Chem. A

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“…From the method of choice, among seven tested functionals, the most suitable method for reproducing the enol absorption spectra of all molecules is the B3LYP because this method provides the most satisfactory agreement with the experimental data. Moreover, previous studies have been proven that the B3LYP and TD-B3LYP functionals with TZVP basis set are suitable to describe electronic and photophysical properties as well as the PT process of ESIPT molecules [29,[57][58][59][60][61][62]. Therefore, the B3LYP was further em ployed to optimize the enol form in the S 1 state and the keto form both in S 0 and the S 1 states of all molecules.…”

Section: Static Calculationsmentioning

confidence: 99%

“…3-Hydroxyflavone (3HF), one of the flavonol family as shown in Fig. 1 (when X = O), has been not only used as fluorescent probes but also as a model molecule to study the ESIPT process due to its unique large Stokes shift (190 nm) [25] and dual emissions [26][27][28][29]. However, a wider application of 3HF as a fluorescent probe has been limited due to its enol absorption and keto emission not being in the longer wavelength, the proper ratio of dual emission (N * /I * ) and low intensity of fluorescence.…”

Section: Introductionmentioning

confidence: 99%

Heteroatom substitution effect on electronic structures, photophysical properties, and excited-state intramolecular proton transfer processes of 3-hydroxyflavone and its analogues: A TD-DFT study

Sukpattanacharoen

Salaeh

Promarak

et al. 2019

Journal of Molecular Structure

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The effects of the electron-donating capacity altered by heteroatom substituents on the electronic structures, photophysical properties, and excited-state intramolecular proton transfer (ESIPT) processes of 3HX analogues (3HF, 3HQ, 3HTF, and 3HSO where X = O, NH, S, and SO 2 , respectively) have been investigated by both static calculations and dynamic simulations using density functional theory (DFT) and time-dependent DFT (TD-DFT) methods at B3LYP/TZVP level for ground state (S 0 ) and excited-state (S 1 ), respectively. The static results indicate that the intramolecular hydrogen bonds of all molecules are strengthened in the S 1 , confirmed by the red-shift of IR vibrational spectra and the topology analysis. Heteroatom substitutions cause the red-shift on enol absorption and keto emission spectra of 3HX with relatively larger Stoke shift corresponding to their HOMO−LUMO gaps compared with that of 3HF. Frontier molecular orbitals (MOs) show that upon the photoexcitation, the charge redistribution between the proton donor and proton acceptor groups have induced the ESIPT process. Moreover, the potential energy curves (PECs) of proton transfer (PT) processes of all molecules reveal that the PT processes of all molecules are most likely to proceed in the S 1 state because of low barriers and exothermic reaction. The chance of ESIPT for all molecules is in this order: 3HSO > 3HTF > 3HF > 3HQ. The results of dynamic simulations confirm that the ESIPT processes of all molecules easily occur with the ultrafast time scale (48, 55, 60, 70 fs for 3HSO, 3HTF, 3HF, and 3HQ, respectively). Furthermore, the PT time is anti-correlated with the electronegativity of heteroatoms in 3HX, supported by Mulliken analysis. The ESIPT process of 3HSO is the fastest among 3HX in accordance with its highest intramolecular hydrogen bond strength, lowest PT barrier, and highest exothermic reaction. Nevertheless, after the ESIPT is complete, the twisted structure of 3HSO has initiated the conical intersection, leading to no keto emission observed in the experiment.

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“…[3][4][5][6] One of the most intriguing phenomena in the photochemistry of hydroxychromones (HCs) and their derivatives is the ultrafast (subpicosecond timescale, cf., Table 1) excited-state intramolecular proton transfer (ESIPT) reaction. [11][12][13][14][15][16][17][18] Upon photoexcitation to the low-lying singlet excited states, these molecules would exhibit the proton transfer process where the proton of hydroxyl group is transferred to the carbonyl group without affecting the structural rigidity of benzopyran (see Figure 1). Experimentally observed faster rate of keto tautomer product formation was accounted for the "promoting effect" of a lowfrequency O─H in-plane bending vibration.…”

Section: Introductionmentioning

confidence: 99%

Excited‐state intramolecular proton transfer driven by conical intersection in hydroxychromones

2020

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Nonradiative decay pathways associated with vibronically coupled S1(ππ*)–S2(nπ*) potential energy surfaces of 3‐ and 5‐hydroxychromones are investigated by employing the linear vibronic coupling approach. The presence of a conical intersection close to the Franck–Condon point is identified based on the critical examination of computed energetics and structural parameters of stationary points. We show that very minimal displacements of relevant atoms of intramolecular proton transfer geometry are adequate to drive the molecule toward the conical intersection nuclear configuration. The evolving wavepacket on S1(ππ*) bifurcates at the conical intersection: a part of the wavepacket moves to S2(nπ*) within a few femtoseconds while the other decays to S1 minimum. Our findings indicate the possibility of forming the proton transfer tautomer product via S2(nπ*), competing with the traditional pathway occurring on S1(ππ*).

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Excited-State Intramolecular Proton Transfer Reaction of 3-Hydroxyflavone

Cited by 18 publications

References 53 publications

Molecular Dynamics Simulation of the Excited-State Proton Transfer Mechanism in 3-Hydroxyflavone Using Explicit Hydration Models

Molecular Dynamics Simulation of the Excited-State Proton Transfer Mechanism in 3-Hydroxyflavone Using Explicit Hydration Models

Heteroatom substitution effect on electronic structures, photophysical properties, and excited-state intramolecular proton transfer processes of 3-hydroxyflavone and its analogues: A TD-DFT study

Excited‐state intramolecular proton transfer driven by conical intersection in hydroxychromones

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