Parameterization of a linear vibronic coupling model with multiconfigurational electronic structure methods to study the quantum dynamics of photoexcited pyrene

Aleotti, Flavia; Aranda, Daniel; Jouybari, Martha Yaghoubi; Garavelli, Marco; Nenov, Artur; Santoro, Fabrizio

doi:10.1063/5.0044693

Cited by 22 publications

(39 citation statements)

References 76 publications

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“…However, such vibronic effects are not captured in the single-trajectory Ehrenfest scheme adopted here, which predominantly describes the explicitly triggered, totally symmetric Franck–Condon dynamics. Thus, regardless of state ordering, we will miss the gradual population transfer to 1 1 B 2u , which is known to occur in the molecule after photo-excitation of 1 1 B 3u . − We therefore assume that our approach is valid only for a few vibrational cycles after laser excitation.…”

Section: Resultsmentioning

confidence: 99%

Laser-Induced Electronic and Vibronic Dynamics in the Pyrene Molecule and Its Cation

2021

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Among polycyclic aromatic hydrocarbons, pyrene is widely used as an optical probe thanks to its peculiar ultraviolet absorption and infrared emission features. Interestingly, this molecule is also an abundant component of the interstellar medium, where it is detected via its unique spectral fingerprints. In this work, we present a comprehensive first-principles study on the electronic and vibrational response of pyrene and its cation to ultrafast, coherent pulses in resonance with their optically active excitations in the ultraviolet region. The analysis of molecular symmetries, electronic structure, and linear optical spectra is used to interpret transient absorption spectra and kinetic energy spectral densities computed for the systems excited by ultrashort laser fields. By disentangling the effects of the electronic and vibrational dynamics via ad hoc simulations with stationary and moving ions, and, in specific cases, with the aid of auxiliary model systems, we rationalize that the nuclear motion is mainly harmonic in the neutral species, while strong anharmonic oscillations emerge in the cation, driven by electronic coherence. Our results provide additional insights into the ultrafast vibronic dynamics of pyrene and related compounds and set the stage for future investigations on more complex carbon-conjugated molecules.

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Section: Resultsmentioning

confidence: 99%

Laser-Induced Electronic and Vibronic Dynamics in the Pyrene Molecule and Its Cation

2021

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“…Recently, for instance, some of us adopted RASPT2/RASSCF to parametrize an LVC model to study photoexcited pyrene. 18 However, as previously done for DNA nucleobases and Gquadruplexes, [13][14][15]17,63 here we define these quantities within the framework of TD-DFT. The derivation has been presented in previous papers, 15,63 and we also include it in Section S1.1 (Supporting Information (SI)), as we have found a more computationally efficient method of calculating the overlap matrix.…”

Section: Methodsmentioning

confidence: 99%

Fragment Diabatization Linear Vibronic Coupling Model for Quantum Dynamics of Multichromophoric Systems: Population of the Charge-Transfer State in the Photoexcited Guanine–Cytosine Pair

Green

Jouybari

Asha

et al. 2021

J. Chem. Theory Comput.

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We introduce a method (FrD-LVC) based on a fragment diabatization (FrD) for the parametrization of a Linear Vibronic Coupling (LVC) model suitable for studying the photophysics of multichromophore systems. In combination with effective quantum dynamics (QD) propagations with multilayer multiconfigurational time-dependent Hartree (ML-MCTDH), the FrD-LVC approach gives access to the study of the competition between intra-chromophore decays, like those at conical intersections, and inter-chromophore processes, like exciton localization/delocalization and the involvement of charge transfer (CT) states. We used FrD-LVC parametrized with TD-DFT calculations, adopting either CAM-B3LYP or ωB97X-D functionals, to study the ultrafast photoexcited QD of a Guanine-Cytosine (GC) hydrogen bonded pair, within a Watson-Crick arrangement, considering up to 12 coupled diabatic electronic states and the effect of all the 99 vibrational coordinates. The bright excited states localized on C and, especially, on G are predicted to be strongly coupled to the G->C CT state which is efficiently and quickly populated after an excitation to any of the four lowest energy bright local excited states. Our QD simulations show that more than 80% of the excited population on G and ~50% of that on C decays to this CT state in less than 50 fs. We investigate the role of vibronic effects in the population of the CT state and show it depends mainly on its large reorganization energy so that it can occur even when it is significantly less stable than the bright states in the Franck-Condon region.At the same time, we document that the formation of the GC pair almost suppresses the involvement of dark nπ* excited states in the photoactivated dynamics. File list (2) download file view on ChemRxiv main_FrD-LVC.pdf (2.14 MiB) download file view on ChemRxiv SI_FrD-LVC.pdf (4.59 MiB)

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“…We consider 3 different choices of reference states in order to examine their effect on the LVC model, and resultant dynamics. We set the reference states as equivalent to the adiabatic states of the MC at the reference geometry and label this as the standard LVC (St-LVC) approach. This is a typical choice adopted for LVC models, and we have used this method previously in the study of individual chromophores. ,− We use our recently proposed fragment diabatization (FrD) technique to define the reference states . In this approach, the reference states are the adiabatic states of the isolated fragments of the MC (for LEs), or one electron transitions between orbitals on different fragments (for CT states).…”

Section: Methodsmentioning

confidence: 99%

“…We set the reference states as equivalent to the adiabatic states of the MC at the reference geometry and label this as the standard LVC (St-LVC) approach. This is a typical choice adopted for LVC models, and we have used this method previously in the study of individual chromophores. ,− …”

Section: Methodsmentioning

confidence: 99%

The Ultrafast Quantum Dynamics of Photoexcited Adenine–Thymine Basepair Investigated with a Fragment-based Diabatization and a Linear Vibronic Coupling Model

et al. 2021

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In this contribution we present a quantum dynamical study of the photoexcited hydrogen bonded base pair adenine−thymine (AT) in a Watson−Crick arrangement. To that end, we parametrize Linear Vibronic Coupling (LVC) models with Time-Dependent Density Functional Theory (TD-DFT) calculations, exploiting a fragment diabatization scheme (FrD) we have developed to define diabatic states on the basis of individual chromophores in a multichromophoric system. Wavepacket propagations were run with the multilayer extension of the Multiconfiguration Time-Dependent Hartree method. We considered excitations to the three lowest bright states, a ππ* state of thymine and two ππ* states (L a and L b ) of adenine, and we found that on the 100 fs time scale the main decay pathways involve intramonomer population transfers toward nπ* states of the same nucleobase. In AT this transfer is less effective than in the isolated nucleobases, because hydrogen bonding destabilizes the nπ* states. The population transfer to the A → T charge transfer state is negligible, making the ultrafast (femtosecond) decay through the proton coupled electron transfer mechanism unlikely, in line with experimental results in apolar solvents. The excitation energy transfer is also very small. We carefully compare the predictions of LVC Hamiltonians obtained with different sets of diabatic states, defined so to match either local states of the two separated monomers or the base pair adiabatic states in the Franck−Condon region. To that end we also extend the flexibility of the FrD-LVC approach, introducing a new strategy to define fragments diabatic states that account for the effect of the rest of the multichromohoric system through a Molecular Mechanics potential.

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Parameterization of a linear vibronic coupling model with multiconfigurational electronic structure methods to study the quantum dynamics of photoexcited pyrene

Abstract: Paper published as part of the special topic on Quantum Dynamics with ab Initio Potentials ARTICLES YOU MAY BE INTERESTED IN Modern quantum chemistry with [Open]Molcas

Cited by 22 publications

References 76 publications

Laser-Induced Electronic and Vibronic Dynamics in the Pyrene Molecule and Its Cation

Laser-Induced Electronic and Vibronic Dynamics in the Pyrene Molecule and Its Cation

Fragment Diabatization Linear Vibronic Coupling Model for Quantum Dynamics of Multichromophoric Systems: Population of the Charge-Transfer State in the Photoexcited Guanine–Cytosine Pair

The Ultrafast Quantum Dynamics of Photoexcited Adenine–Thymine Basepair Investigated with a Fragment-based Diabatization and a Linear Vibronic Coupling Model

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