A reliable method for fitting TD-DFT transitions to experimental UV–visible spectra

Brémond, Éric; Kieffer, Jérôme; Adamo, Carlo

doi:10.1016/j.theochem.2010.04.038

Cited by 51 publications

(21 citation statements)

References 19 publications

(17 reference statements)

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“…The scale factor S was adjusted manually, on a trial-and-error basis, to reproduce the intensity of experimental spectra, whereas σ i was fixed to 0.5 eV. Calculated spectra were finally converted to the wavelength scale (nm) to be compared to experimental spectra [33].…”

Section: Methodsmentioning

confidence: 99%

The Antioxidant Activity of Quercetin in Water Solution

et al. 2017

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Despite its importance, little is known about the absolute performance and the mechanism for quercetin’s antioxidant activity in water solution. We have investigated this aspect by combining differential oxygen-uptake kinetic measurements and B3LYP/6311+g (d,p) calculations. At pH = 2.1 (30 °C), quercetin had modest activity ( k inh = 4.0 × 10 3 M −1 s −1 ), superimposable to catechol. On raising the pH to 7.4, reactivity was boosted 40-fold, trapping two peroxyl radicals in the chromen-4-one core and two in the catechol with k inh of 1.6 × 10 5 and 7.0 × 10 4 M −1 s −1 . Reaction occurs from the equilibrating mono-anions in positions 4′ and 7 and involves firstly the OH in position 3, having bond dissociation enthalpies of 75.0 and 78.7 kcal/mol, respectively, for the two anions. Reaction proceeds by a combination of proton-coupled electron-transfer mechanisms: electron–proton transfer (EPT) and sequential proton loss electron transfer (SPLET). Our results help rationalize quercetin’s reactivity with peroxyl radicals and its importance under biomimetic settings, to act as a nutritional antioxidant.

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Section: Methodsmentioning

confidence: 99%

The Antioxidant Activity of Quercetin in Water Solution

et al. 2017

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“…Before discussing these results, however, it should be noted that the procedure to estimate absorption maxima as vertical S 0 → S 1 excitation energies (and hence emission maxima as vertical S 1 → S 0 emission energies) was, in a number of cases, validated by also computing the full UV-vis spectra by convoluting several tens of transitions with Gaussian functions of fixed full width at half maximum (set to the standard value of 0.5 eV [66]). Thereby, in support of the current procedure, the differences between the Gaussian-convoluted Q-band absorption maxima and the corresponding S 0 → S 1 excitation energies were found to be very small (<0.02 eV).…”

Section: Influence On Spectroscopic Parameters: Td-dft Calculations Wmentioning

confidence: 99%

Red-light absorption and fluorescence of phytochrome chromophores: A comparative theoretical study

Falklöf¹,

Durbeej²

2013

Chemical Physics

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Currently, much experimental effort is being invested in the engineering of phytochromes, a large superfamily of photoreceptor proteins, into fluorescent proteins suitable for bioimaging in the near-infrared regime. In this work, we gain insight into the potential of computational methods to contribute to this development by investigating how well representative quantum chemical methods reproduce recently recorded red-light absorption and emission maxima of synthetic derivatives of the bilin chromophores of phytochromes. Focusing on the performance of time-dependent density functional theory but using also the ab initio CIS(D), CC2 and CASPT2 methods, we explore how various methodological considerations influence computed spectra and find, somewhat surprisingly, that density functionals lacking exact exchange reproduce the experimental measurements with smaller errors than functionals that include exact exchange. Thus, for the important class of chromophores that bilins constitute, the widely established trend that hybrid functionals give more accurate excitation energies than pure functionals does not apply.

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“…Vertical excitation UV–vis spectra were calculated using a variety of TD functionals with the 6‐31+G(d) basis set (Table 1). This basis set has been shown to be adequate in previous studies for the calculation of the vertical nonequilibrium excitation spectra (45–50). The adequacy can also be inferred from a comparison of the results for the calculation of the vertical nonequilibrium excitation spectra and state‐specific corrected absorption and emission spectra, which were calculated using a 6‐31+G(d,p) basis set.…”

Section: Methodsmentioning

confidence: 99%

Photophysical Properties of Fluorescent 2‐(Phenylamino)‐1,10‐phenanthroline Derivatives^†

Teixeira

Silva

Gaspar

et al. 2020

Photochem & Photobiology

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The present study details the experimental and theoretical characterization of the photophysical properties of 14 examples of 2‐(phenylamino)‐1,10‐phenanthrolines (1). The absorption spectra of 1 are substituent‐dependent but in a general manner present absorption bands at wavelengths of ~230; ~300; ~335 and a shoulder at ~380 nm. Electron‐donating groups (EDG) and electron‐withdrawing groups (EWG), respectively, result in bathochromic and hypsochromic shifts. Compounds 1 are highly luminescent, in contrast to phenanthroline, and emit in the region between 350 and 500 nm with substituent‐dependent λmax emission. The emission spectra show a redshift for EDG (4‐OMe 62 nm; 4‐Me 19 nm) and a blueshift for EWG (4‐CN 41 nm; 4‐CF3 38 nm) relative to the emission of the unsubstituted parent compound 1a. Plotting the λmaxEM against Hammett σ+ constants gave an excellent linear correlation demonstrating the electron‐deficient nature of the excited state and how the substituents (de)stabilize S1. Theoretical calculations revealed a HOMO‐LUMO π‐π* electronic transition to S1 which in combination with difference (S1–S0) in electron density maps revealed charge‐transfer character. Strongly electron‐withdrawing substituents switch off the charge transfer to give rise to a local excitation.

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A reliable method for fitting TD-DFT transitions to experimental UV–visible spectra

Cited by 51 publications

References 19 publications

The Antioxidant Activity of Quercetin in Water Solution

The Antioxidant Activity of Quercetin in Water Solution

Red-light absorption and fluorescence of phytochrome chromophores: A comparative theoretical study

Photophysical Properties of Fluorescent 2‐(Phenylamino)‐1,10‐phenanthroline Derivatives^†

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A reliable method for fitting TD-DFT transitions to experimental UV–visible spectra

Cited by 51 publications

References 19 publications

The Antioxidant Activity of Quercetin in Water Solution

The Antioxidant Activity of Quercetin in Water Solution

Red-light absorption and fluorescence of phytochrome chromophores: A comparative theoretical study

Photophysical Properties of Fluorescent 2‐(Phenylamino)‐1,10‐phenanthroline Derivatives†

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Product

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Photophysical Properties of Fluorescent 2‐(Phenylamino)‐1,10‐phenanthroline Derivatives^†