On the ultrafast charge migration and subsequent charge directed reactivity in Cl⋯N halogen-bonded clusters following vertical ionization

Chandra, Sankhabrata; Periyasamy, Ganga; Bhattacharya, Atanu

doi:10.1063/1.4922843

Cited by 13 publications

(24 citation statements)

References 62 publications

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“…In order to explore different facets of pure electronelectron correlation-and relaxation-driven charge migration through halogen bonds, vertical ionization scheme is adopted, which is discussed in detail elsewhere. 14 The process of vertical ionization manifests removal of an electron from a molecular cluster and therefore, it creates a 'hole' in the electronic cloud. The subsequent charge migration dynamics is nothing but the time-evolution of this hole.…”

Section: Theoretical Methodsmentioning

confidence: 99%

“…Recently, we have explored pure electron-electron correlation-and relaxation-driven charge migration dynamics through the Cl ..... N halogen bonded clusters following vertical ionization for different A-Cl (A represents F, OH, CN, NH 2 , CF 3 and COOH substituents) molecules paired with NH 3 molecule. 14,15 In the vertical ionization scheme, an electron is ejected from the highest occupied molecular orbital (HOMO) and thus, we create a hole in electron cloud of these complexes. Upon removal of an electron from the HOMO of NCCl ..... NH 3 complex, the hole is predicted to migrate from the NH 3 -end to the ClCN-end of the complex in approximately 500 attosecond.…”

Section: Introductionmentioning

confidence: 99%

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On the Attosecond charge migration in Cl…..N, Cl…..O, Br…..N and Br…..O Halogen-bonded clusters: Effect of donor, acceptor, vibration, rotation, and electron correlation

2016

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The electron-electron relaxation and correlation-driven charge migration process, which features pure electronic aspect of ultrafast charge migration phenomenon, occurs on a very short timescale in ionized molecules and molecular clusters, prior to the onset of nuclear motion. In this article, we have presented nature of ultrafast pure electronic charge migration dynamics through Cl ..... N, Cl ..... O, Br ..... N, and Br ..... O halogen bonds, explored using density functional theory. We have explored the role of donor, acceptor, electron correlation, vibration and rotation in charge migration dynamics through these halogen bonds. For this work, we have selected ClF, Cl 2 , ClOH, ClCN, BrF, BrCl, BrOH, and BrCN molecules paired with either NH 3 or H 2 O. We have found that the timescale for pure electron-electron relaxation and correlation-driven charge migration through the Cl ..... N, Br ..... N, Cl ..... O, and Br ..... O halogen bonds falls in the range of 300-600 attosecond. The primary driving force behind the attosecond charge migration through the Cl ..... N, Br ..... N, Cl ..... O, and Br ..... O halogen bonds is the energy difference (E) between two stationary cationic orbitals (LUMO-β and HOMOβ), which together represents the initial hole density immediately following vertical ionization. We have also predicted that the strength of electron correlation has significant effect on the charge migration timescale in Cl ..... N, Br ..... N, Cl ..... O, and Br ..... O halogen bonded clusters. Vibration and rotation are also found to exhibit profound effect on attosecond charge migration dynamics through halogen bonds.

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Section: Theoretical Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

On the Attosecond charge migration in Cl…..N, Cl…..O, Br…..N and Br…..O Halogen-bonded clusters: Effect of donor, acceptor, vibration, rotation, and electron correlation

2016

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“…Further, hole migration after ionization is explored by measuring the time scale for evolution of the hole created after vertical ionization. 21,41 Time evolution of the hole created by ionization can occur at a much faster time scale than that for nuclear dynamics. Hence, frozen frame nuclei at the vertical ion (VI) point have been considered to solve the time-dependent Schrodinger equation.…”

Section: ■ Computational Methodsmentioning

confidence: 99%

Computational Studies on Structural, Excitation, and Charge-Transfer Properties of Ureidopeptidomimetics

2016

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Peptides with ureido group enclosing backbones are considered peptidomimetics and are known for their higher stabilities, biocompatibilities, antibiotic, inhibitor, and charge-transduction activities. These peptidomimetics have some unique applications, which are quite different from those of natural peptides. Hence, it is imperative to appreciate their properties at a microscopic level. In this regard, this work outlines, in detail, the charge transfer (CT) properties, holemigration dynamics, and electronic structures of various experimentally comprehended ureidopeptidomimetic models using density functional theory (DFT). Time-dependent DFT and complete active space self-consistent field computations on basic models provide the necessary evidence for the viability of CT from the end enfolding the ureido group to the other end with a carboxylate entity. This donor-to-acceptor CT has been reflected in excitation studies, in which the higher intensity band corresponds to CT from the π orbital of the ureido group to the π* orbital of the carboxylate entity. Further, hole-migration studies have shown that charge can evolve from the ureido end, whereas the hole generated at the carboxylate end does not migrate. However, hole migration has been reported to occur from both ends (amino and carboxylate ends) in glycine oligopeptides, and our studies show that the ability to transfer and migrate charge can be tuned by modifying the donor and acceptor functional groups in both the neutral and cationic charge states. We have analyzed the possibility of hole migration following ionization using DFT-based wave-packet propagation and found its occurrence on a ∼2−5 fs time scale, which reflects the charge-transduction ability of peptidomimetics.

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“…The Ehrenfest Eqs. (26) and (27) are obtained by taking the classical limit as shown above in Sect. 3.3.…”

Section: One-configuration and Classical Limitsmentioning

confidence: 99%

“…With the population of a superposition of electronic states, the convenient picture of a single potential energy surface is lost: the nuclei "feel" the multiple coupled potential energy surfaces. Such coupled electron-nuclear dynamics is often called charge-directed reactivity in the literature [25,26].…”

Section: Introductionmentioning

confidence: 99%

Direct methods for non-adiabatic dynamics: connecting the single-set variational multi-configuration Gaussian (vMCG) and Ehrenfest perspectives

2016

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coordinates, respectively. The Hamiltonian operator reads: Ĥ (r, R) =T n (R) +T e (r) + V n−e (r, R) =T n (R) +Ĥ e (r, R) , with T n (R) the kinetic energy operator of the nuclei, T e (r) the kinetic energy operator of the electrons, V n−e (r, R) which includes all inter-particles interactions (electron-electron, nucleus-nucleus and electron-nucleus) and Ĥ e (r, R) =T e (r) + V n−e (r, R) the electronic Hamiltonian for fixed nuclei R. Unfortunately, this equation is impossible to solve analytically for more than two particles, i.e. the hydrogen atom. The field of theoretical chemistry is thus dominated by developments of numerical and approximate methods, which can be used to treat other atoms and molecules.Conventional Born-Oppenheimer molecular dynamics only allows one to simulate nuclear motion on a single potential energy surface and therefore does not describe non-adiabatic processes involving non-radiative electronic transitions. Standard grid-based quantum mechanical simulations are expensive computationally because of their exponential scaling with the system size. A separate bottleneck is the computation and fitting of the potential energy surfaces prior to any dynamics calculation. Reducing the number of nuclear degrees of freedom of the system is sometimes done to make the calculation feasible, but the validity of this approximation is limited [2][3][4]. "On-the-fly" dynamics methods have been developed to address these issues. They are referred to as direct dynamics methods since the potential energy surfaces are calculated as needed along nuclear trajectories, thus avoiding the precomputation of globally fitted surfaces, and sampling only the relevant regions of the potential energy surfaces. These nuclear trajectories are used to describe the nuclear wave packet motion, i.e. the nuclear wave packet is expanded in the basis of nuclear trajectories via expansion coefficients.Abstract In this article, we outline the current state-of-theart "on-the-fly" methods for non-adiabatic dynamics, highlighting the similarities and differences between them. We derive the equations of motion for both the Ehrenfest and variational multi-configuration Gaussian (vMCG) methods from the Dirac-Frenkel variational principle. We explore the connections between these two methods by presenting an alternative derivation of the vMCG method, which gives the Ehrenfest equations of motion when taking the appropriate limits.

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On the ultrafast charge migration and subsequent charge directed reactivity in Cl⋯N halogen-bonded clusters following vertical ionization

Cited by 13 publications

References 62 publications

On the Attosecond charge migration in Cl…..N, Cl…..O, Br…..N and Br…..O Halogen-bonded clusters: Effect of donor, acceptor, vibration, rotation, and electron correlation

On the Attosecond charge migration in Cl…..N, Cl…..O, Br…..N and Br…..O Halogen-bonded clusters: Effect of donor, acceptor, vibration, rotation, and electron correlation

Computational Studies on Structural, Excitation, and Charge-Transfer Properties of Ureidopeptidomimetics

Direct methods for non-adiabatic dynamics: connecting the single-set variational multi-configuration Gaussian (vMCG) and Ehrenfest perspectives

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