Importance of Vibronic Effects in the UV–Vis Spectrum of the 7,7,8,8-Tetracyanoquinodimethane Anion

Tapavicza, Enrico; Furche, Filipp; Sundholm, Dage

doi:10.1021/acs.jctc.6b00720

Cited by 40 publications

(67 citation statements)

References 88 publications

(168 reference statements)

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“…The RADLESS module was used for the simulation of vibronic absorption and fluorescence spectra. 20,21 The resolution of the calculated spectra can be raised by increasing the integration time. An integration time of 2.42 ps was found to be proficient for the comparison with the experimental spectra.…”

Section: Methodsmentioning

confidence: 99%

“…19 The geometric displacement and the Duschinsky rotation matrix are used to construct a generating function that allows the simulation of absorption and fluorescence spectra within the zerotemperature approximation. This method has been developed and implemented by Tapavicza et al 20,21 The simulated spectra can be compared with ultraviolet-visible (UV-Vis) absorption and fluorescence spectra measured by matrix isolation spectroscopy. Absorption spectra for the perylene, terrylene and quaterrylene molecules have been recorded by Halasinski et al 22 The absorption and fluorescence spectra of perylene have been recorded by Joblin et al 23 As with all DFT methods the choice of the correct functional is significant for the accuracy of the calculated results.…”

Section: Introductionmentioning

confidence: 99%

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Calculation of vibrationally resolved absorption and fluorescence spectra of the rylenes

Greiner

Sundholm

2020

Phys. Chem. Chem. Phys.

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A generating function method was used to simulate the vibrationally resolved absorption and emission spectra of perylene, terrylene and quaterrylene. This method operates on the basis of adiabatic excitation energies and electronic ground and excited state vibrational frequencies. These parameters were calculated using density functional theory with the PBE0 functional for perylene and terrylene and with the BH-LYP functional for quaterrylene. The vertical excitation energies of the lower excited states were calculated using functionals with differing amounts of Hartree-Fock exchange. The optimal functional for each molecule was chosen by comparing these energies to literature excitation energies. Using this technique the calculated absorption spectra and the calculated emission spectrum of perylene were found to be in excellent agreement with the literature experimental spectra after introducing a shift and a scaling factor. The most prominent bands of the absorption spectra were assigned to their respective vibronic transitions. † Electronic supplementary information (ESI) available: The Cartesian ground and excited state coordinates of the optimized molecular structures, the oscillator strengths of the vertical excitations and the calculated ground and excited state harmonic frequencies of the studied molecules are given as supporting information. All assigned bands in the calculated absorption spectra with a relative intensity of above 2%. See

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Calculation of vibrationally resolved absorption and fluorescence spectra of the rylenes

Greiner

Sundholm

2020

Phys. Chem. Chem. Phys.

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“…For many small chromophores in solution, the optical absorption spectra are known to have a significant contribution from vibronic states and a simulation of the spectrum in the form of Eqn. 3 often fails in reproducing the fine structure of the spectral shape, as well as its width [8,34].…”

Section: B the Ensemble Approachmentioning

confidence: 99%

“…In order to treat vibronic effects in the absorption spectra of small dyes, it is necessary to account for the quantum nature of the nuclei. Working under the Born-Oppenheimer approximation, such that the total wave function of the system is separable into a nuclear and an electronic part, the absorption cross section for a given excitation from electronic state i to electronic state f can be written as [34,43,44]:…”

Section: Franck-condon Spectramentioning

confidence: 99%

Combining the ensemble and Franck-Condon approaches for calculating spectral shapes of molecules in solution

Zuehlsdorff

Isborn

2018

The Journal of Chemical Physics

127

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The correct treatment of vibronic effects is vital for the modeling of absorption spectra of many solvated dyes. Vibronic spectra for small dyes in solution can be easily computed within the Franck-Condon approximation using an implicit solvent model. However, implicit solvent models neglect specific solute-solvent interactions on the electronic excited state. On the other hand, a straightforward way to account for solute-solvent interactions and temperature-dependent broadening is by computing vertical excitation energies obtained from an ensemble of solute-solvent conformations. Ensemble approaches usually do not account for vibronic transitions and thus often produce spectral shapes in poor agreement with experiment. We address these shortcomings by combining zero-temperature vibronic fine structure with vertical excitations computed for a room-temperature ensemble of solute-solvent configurations. In this combined approach, all temperature-dependent broadening is treated classically through the sampling of configurations and quantum mechanical vibronic contributions are included as a zero-temperature correction to each vertical transition. In our calculation of the vertical excitations, significant regions of the solvent environment are treated fully quantum mechanically to account for solute-solvent polarization and charge-transfer. For the Franck-Condon calculations, a small amount of frozen explicit solvent is considered in order to capture solvent effects on the vibronic shape function. We test the proposed method by comparing calculated and experimental absorption spectra of Nile red and the green fluorescent protein chromophore in polar and non-polar solvents. For systems with strong solute-solvent interactions, the combined approach yields significant improvements over the ensemble approach. For systems with weak to moderate solute-solvent interactions, both the high-energy vibronic tail and the width of the spectra are in excellent agreement with experiments.

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“…The broadened spectra were then averaged to obtain the absorption spectrum of the macroscopic ensemble. 41 Although this treatment neglects the quantum nature of the nuclear vibrations, 46 the influence of different conformations will be visible in the spectrum. …”

Section: Electronic Absorption Spectramentioning

confidence: 99%

The role of tachysterol in vitamin D photosynthesis – a non-adiabatic molecular dynamics study

Cisneros

Thompson

Baluyot

et al. 2017

Phys. Chem. Chem. Phys.

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To investigate the role of tachysterol in the photophysical/photochemical regulation of vitamin D photosynthesis, we studied its electronic absorption properties and excited state dynamics using time-dependent density functional theory (TDDFT), second-order approximate coupled cluster theory (CC2), and non-adiabatic surface hopping molecular dynamics in the gas phase. In excellent agreement with experiments, the simulated electronic spectrum shows a broad absorption band with a remarkably higher extinction coefficient than the other vitamin D photoisomers provitamin D, lumisterol, and previtamin D. The broad band arises from the spectral overlap of four different ground state rotamers. After photoexcitation, the first excited singlet state (S 1 ) decays with a lifetime of 882 fs. The S 1 dynamics is characterized by a strong twisting of the central double bond. In 96% of all trajectories this is followed by unreactive relaxation to the ground state near a conical intersection. The double-bond twisting in the chemically unreactive trajectories induces a strong interconversion between the different rotamers. In 2.3 % of the trajectories we observed [1,5]-sigmatropic hydrogen shift forming the partly deconjugated toxisterol D1. 1.4 % previtamin D formation is observed via hula-twist double bond isomerization. In both reaction channels, we find a strong dependence between photoreactivity and dihedral angle conformation: hydrogen shift only occurs in cEc and cEt rotamers and double bond isomerization occurs mainly in cEc rotamers. Hence, our study confirms the previously formed hypothesis that cEc rotamers are more prone to previtamin D formation than other isomers. In addition, we also observe the formation of a cyclobutene-toxisterol in the hot ground state in 3 trajectories (0.7 %).Due to its large extinction coefficient and mostly unreactive behavior, tachysterol acts mainly as a sun shield suppressing previtamin D formation. Tachysterol shows stronger toxisterol formation than previtamin D and can thus be seen as the major degradation route of vitamin D. Absorption of low energy ultraviolet light by the cEc rotamer can lead to previtamin D formation. In addition the cyclobutene-toxisterol, which possibly reacts thermally to previtamin D, is also preferably formed at long 2 wavelengths. These two mechanisms are consistent with the wavelength dependent photochemistry found in experiments. Our study reinforces a recent hypothesis that tachysterol constitutes a source of previtamin D when only low energy ultraviolet light is available, as it is the case in winter or in the morning and evening hours of the day.3

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Importance of Vibronic Effects in the UV–Vis Spectrum of the 7,7,8,8-Tetracyanoquinodimethane Anion

Cited by 40 publications

References 88 publications

Calculation of vibrationally resolved absorption and fluorescence spectra of the rylenes

Calculation of vibrationally resolved absorption and fluorescence spectra of the rylenes

Combining the ensemble and Franck-Condon approaches for calculating spectral shapes of molecules in solution

The role of tachysterol in vitamin D photosynthesis – a non-adiabatic molecular dynamics study

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