Dataset Information

Absorption and Emission Spectra of a Flexible Dye in Solution: a Computational Time-Dependent Approach.

ABSTRACT: The spectroscopic properties of the organic chromophore 4-naphthoyloxy-1-methoxy-2,2,6,6-tetramethylpiperidine (NfO-TEMPO-Me) in toluene solution are explored through an integrated computational strategy combining a classical dynamic sampling with a quantum mechanical description within the framework of the time-dependent density functional theory (TDDFT) approach. The atomistic simulations are based on an accurately parametrized force field, specifically designed to represent the conformational behavior of the molecule in its ground and bright excited states, whereas TDDFT calculations are performed through a selected combination of hybrid functionals and basis sets to obtain optical spectra closely matching the experimental findings. Solvent effects, crucial to obtain good accuracy, are taken into account through explicit molecules and polarizable continuum descriptions. Although, in the case of toluene, specific solvation is not fundamental, the detailed conformational sampling in solution has confirmed the importance of a dynamic description of the molecular geometry for a reliable description of the photophysical properties of the dye. The agreement between theoretical and experimental data is established and a robust protocol for the prediction of the optical behaviour of flexible fluorophores in solution is set.

SUBMITTER: De Mitri N

PROVIDER: S-EPMC4618302 | biostudies-literature | 2013 Oct

REPOSITORIES: biostudies-literature

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Absorption and Emission Spectra of a Flexible Dye in Solution: a Computational Time-Dependent Approach.

De Mitri Nicola N Monti Susanna S Prampolini Giacomo G Barone Vincenzo V

Journal of chemical theory and computation 20131001 10

The spectroscopic properties of the organic chromophore 4-naphthoyloxy-1-methoxy-2,2,6,6-tetramethylpiperidine (NfO-TEMPO-Me) in toluene solution are explored through an integrated computational strategy combining a classical dynamic sampling with a quantum mechanical description within the framework of the time-dependent density functional theory (TDDFT) approach. The atomistic simulations are based on an accurately parametrized force field, specifically designed to represent the conformational ...[more]

PMID: 26504457

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Project description:A detailed understanding and interpretation of absorption spectra of molecular systems, especially in condensed phases, requires computational models that allow their structural and electronic features to be connected to the observed macroscopic spectra. This work is focused on modeling the electronic absorption spectrum of a fluorescent probe, namely, the 9-(4-((bis(2-((2-(ethylthio)ethyl)thio)ethyl)amino)methyl)phenyl)-6-(pyrrolidin-1-yl)-3H-xanthen-3-one molecule, depicted by a combined classical-quantum chemical approach. Particularly, first classical molecular dynamics (MD) has been used to explore the configurational space, and next, the absorption spectrum has been reconstructed by averaging the results of time-dependent density functional theory (TD-DFT) calculations performed on equispaced molecular conformations extracted from MD to properly sample the configurational space explored at finite temperature. To verify the effect of molecular conformation on the spectral profile, the generated electronic absorption spectra were compared with those obtained considering a single structure corresponding to the optimized one, an approach also referred to as static. This comparison allows one to highlight a sizable though small shift between the maxima of the corresponding reconstructed absorption spectra, highlighting the importance of conformational sampling in the case of this rather flexible molecule. Four different exchange and correlation functionals (PBE, BLYP, PBE0, B3LYP) were considered to compute vertical transition via TD-DFT calculations. From the results obtained in gas and in condensed, here solution, phases, it appears that the magnitude of the shift is actually more affected by the phase in which the system is found than by the functional used. This fact underlines the central importance of conformational mobility, that is flexibility, of this molecule. From a more quantitative point of view, a comparison with available experimental data shows that hybrid functionals, such as PBE0 and B3LYP, enable one to faithfully reproduce the observed absorption maxima.

Dataset Information

Absorption and Emission Spectra of a Flexible Dye in Solution: a Computational Time-Dependent Approach.

Publications

Absorption and Emission Spectra of a Flexible Dye in Solution: a Computational Time-Dependent Approach.

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