Quenching of Charge Transfer in Nitrobenzene Induced by Vibrational Motion

Zobel, J. Patrick; Nogueira, Juan J.; González, Leticia

doi:10.1021/acs.jpclett.5b00990

Cited by 26 publications

(54 citation statements)

References 28 publications

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“…Consequently, the experimental spectra show more bands than those predicted computationally. This has already been observed before in other systems (as an example, see the case of nitrobenzene in reference [ 15 ]) and is also the case of the system studied here, because the minimum energy geometry is planar for the most stable trans isomer and, for example, nπ* transitions have strictly zero transition dipole strength. For this reason, in order to reproduce the absorption spectrum, we have used molecular dynamics as a consistent geometry generator to statistically represent 3-PAPy in a real spectroscopic environment at room temperature (298 K).…”

Section: Computational Strategysupporting

confidence: 86%

Phenylazopyridine as Switch in Photochemical Reactions. A Detailed Computational Description of the Mechanism of Its Photoisomerization

et al. 2017

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Azo compounds are organic photochromic systems that have the possibility of switching between cis and trans isomers under irradiation. The different photochemical properties of these isomers make azo compounds into good light-triggered switches, and their significantly different geometries make them very interesting as components in molecular engines or mechanical switches. For instance, azo ligands are used in coordination complexes to trigger photoresponsive properties. The light-induced trans-to-cis isomerization of phenylazopyridine (PAPy) plays a fundamental role in the room-temperature switchable spin crossover of Ni-porphyrin derivatives. In this work, we present a computational study developed at the SA-CASSCF/CASPT2 level (State Averaged Complete Active Space Self Consistent Field/CAS second order Perturbation Theory) to elucidate the mechanism, up to now unknown, of the cis–trans photoisomerization of 3-PAPy. We have analyzed the possible reaction pathways along its lowest excited states, generated by excitation of one or two electrons from the lone pairs of the N atoms of the azo group (nazoπ*2 and nazo2π*2 states), from a π delocalized molecular orbital (ππ* state), or from the lone pair of the N atom of the pyridine moiety (npyπ* state). Our results show that the mechanism proceeds mainly along the rotation coordinate in both the nazoπ* and ππ* excited states, although the nazo2π*2 state can also be populated temporarily, while the npyπ* does not intervene in the reaction. For rotationally constrained systems, accessible paths to reach the cis minimum along planar geometries have also been located, again on the nazoπ* and ππ* potential energy surfaces, while the nazo2π*2 and npyπ* states are not involved in the reaction. The relative energies of the different paths differ from those found for azobenzene in a previous work, so our results predict some differences between the reactivities of both compounds.

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Section: Computational Strategysupporting

confidence: 86%

Phenylazopyridine as Switch in Photochemical Reactions. A Detailed Computational Description of the Mechanism of Its Photoisomerization

et al. 2017

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“…We note that the average nitro group torsion angle of 2NN in the initial conditions (

γ = 10^{\circ}

) is not that of the minimum‐energy geometry (

γ = 0

). Due to the symmetry of the molecule, torsion of the nitro group away from a C s ‐symmetric minimum‐energy ground state to either direction leads to pairs of enantiomers with equivalent physical properties . Thus, rather than using any single CCNO dihedral angles, we take the average of the four CCNO dihedral angles to represent the nitro group torsion γ , which results in an average

γ = 10^{\circ}

for the initial conditions.…”

Section: Resultsmentioning

confidence: 99%

Nonadiabatic Dynamics Simulation Predict Intersystem Crossing in Nitroaromatic Molecules on a Picosecond Time Scale

Zobel

González

2019

ChemPhotoChem

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Previous time‐resolved spectroscopic experiments and static quantum‐chemical calculations attributed nitronaphthalene derivatives one of the fastest time scales for intersystem crossing within organic molecules, reaching the 100 fs mark. Nonadiabatic dynamics simulations on three nitronaphthalene derivatives challenge this view, showing that the experimentally observed ∼100 fs process corresponds to internal conversion in the singlet manifolds. Intersystem crossing, instead, takes place on a longer time scale of ∼1 ps. The dynamics simulations further reveal that the spin transitions occur via two distinct pathways with different contribution for the three systems, which are determined by electronic factors and the torsion of the nitro group. This study, therefore, indicates that the existence of sub‐picosecond intersystem crossing in other nitroaromatic molecules should be questioned.

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“…For these reasons, CT processes have been intensively studied in gas phase or in solution where various parameters can be controlled to tune the CT rate such as the nature of the solvent or the presence of functionalized substituents 8 . In this context, several experimental techniques offer the ability to probe the CT rate, ranging from adsorption/emission spectroscopy 9 to more sophisticated optical pump-probe experiments 10 .…”

Section: Introductionmentioning

confidence: 99%

Probing charge transfer dynamics in a single iron tetraphenylporphyrin dyad adsorbed on an insulating surface

et al. 2018

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Although the dynamics of charge transfer (CT) processes can be probed with ultimate lifetime resolution, the inability to control CT at the nanoscale is one of the most important roadblocks to revealing some of its deep fundamental aspects. In this work, we present an investigation of CT dynamics in a single iron tetraphenylporphyrin (Fe-TPP) donor/acceptor dyad adsorbed on a CaF2/Si(100) insulating surface. The tip of a scanning tunneling microscope (STM) is used to create local ionic states in one fragment of the dyad. The CT process is monitored by imaging subsequent changes in the neighbor acceptor molecule and its efficiency is mapped, revealing the influence of the initial excited state in the donor molecule. In the validation of the experiments, simulations based on density functional theory show that holes have a higher donor-acceptor CT rate compared to electrons and highlight a noticeable initial state dependence on the CT process. We leverage the unprecedented spatial resolution achieved in our experiments to show that the CT process in the dyad is governed via molecule-molecule coherent tunneling with negligible surface-mediated character.

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Quenching of Charge Transfer in Nitrobenzene Induced by Vibrational Motion

Cited by 26 publications

References 28 publications

Phenylazopyridine as Switch in Photochemical Reactions. A Detailed Computational Description of the Mechanism of Its Photoisomerization

Phenylazopyridine as Switch in Photochemical Reactions. A Detailed Computational Description of the Mechanism of Its Photoisomerization

Nonadiabatic Dynamics Simulation Predict Intersystem Crossing in Nitroaromatic Molecules on a Picosecond Time Scale

Probing charge transfer dynamics in a single iron tetraphenylporphyrin dyad adsorbed on an insulating surface

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