References of "Mignolet, Benoît"
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See detailModeling the electron-nuclear dynamics induced by short laser pulses in molecules
Mignolet, Benoît ULiege

Conference (2018, January)

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See detailWhere Ion Mobility and Molecular Dynamics Meet to Unravel the (Un)Folding Mechanisms of an Oligorotaxane Molecular Switch
Hanozin, Emeline ULiege; Mignolet, Benoît ULiege; Morsa, Denis ULiege et al

in ACS Nano (2017), 11(10), 10253-10263

At the interface between foldamers and mechanically interlocked molecules, oligorotaxanes exhibit a spring-like folded secondary structure with remarkable mechanical and physicochemical properties. Among ... [more ▼]

At the interface between foldamers and mechanically interlocked molecules, oligorotaxanes exhibit a spring-like folded secondary structure with remarkable mechanical and physicochemical properties. Among these properties, the ability of oligorotaxanes to act as molecular switches through controlled modulations of their spatial extension over (un)folding dynamics is of particular interest. The present study aims to assess and further characterize this remarkable feature in the gas phase using mass spectrometry tools. In this context, we focused on the [4]5NPR+12 oligorotaxane molecule complexed with PF6 - counterion and probed its co-conformational states as a function of the in-source-generated charge states. Data were interpreted in light of electronic secondary structure computations at the PM6 and DFT levels. Our results highlight two major co-conformational groups associated either with folded compact structures, notably stabilized by intramolecular π-π interactions and predominant for low charge states or with fully stretched structures resulting from significant Coulombic repulsions at high charge states. Between, the oligorotaxane adopts intermediate folded co-conformations, suggesting a stepwise unfolding pathway under increasing repulsive Coulombic constraints. The reversibility of this superstructural transition was next interrogated under electron-driven (nondissociative electron transfer) and heat-driven (collision-induced unfolding) activation stimuli. The outcomes support the feasibility to either unfold or (partially) refold the oligorotaxane foldamer on purpose in the gas phase. Our results show that the balance between the stabilizing π-π interactions and the versatile Coulomb interactions dictates the elongation state of the foldamer in the gas phase and emphasizes the adequacy of mass spectrometry tools for the superstructural characterization of desolvated prototypical artificial molecular machines. © 2017 American Chemical Society. [less ▲]

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See detailCoulombic driven multi-conformational aspects of oligorotaxane switches studied by ion mobility mass spectrometry and molecular dynamics
Hanozin, Emeline ULiege; Mignolet, Benoît ULiege; Morsa, Denis ULiege et al

Conference (2017, June)

Introduction Artificial Molecular Machines (AMMs), such as Mechanically Interlocked Molecules (MIMs) and foldamers, have recently raised tremendous interest due to their unique properties. Under the ... [more ▼]

Introduction Artificial Molecular Machines (AMMs), such as Mechanically Interlocked Molecules (MIMs) and foldamers, have recently raised tremendous interest due to their unique properties. Under the influence of an appropriate stimuli (pH, redox potential, light…), such molecules are able to reversibly switch between distinct conformational states. Scientists may capitalize on such exclusive properties to get a better understanding of the biomacromolecular level or to design innovative “smart” materials. At the interface between foldamers and MIMs, oligorotaxanes exhibit a spring-like folded secondary structure with remarkable mechanical and physicochemical properties. In the present study, we use ion mobility coupled with mass spectrometry (IM-MS) to probe the conformational states of differentially charged oligorotaxanes in the gas phase. Method Oligorotaxanes are donor-acceptor polymers composed of a π electron-donating dumbbell over which a discrete number of π electron-accepting tetracationic cyclophanes are threaded. The numerous intra-molecular interactions provide them a highly-stabilized rigid rod-like structure in solution. We use IM-MS as implemented in the Synapt G2 HDMS (Waters, Manchester, UK) to investigate the structure of the ionized oligorotaxanes. Our purposes are to probe (i) the different populations of stable conformers generated according to the charge state z and (ii) the reversibility of an electron-driven or thermal-driven conformational change in the gas phase implemented via an electron transfer or collisional activation process prior to the mobility separation. Our experimental observations are supported by electronic structure optimizations at the PM6 and DFT levels coupled with Born-Oppenheimer Molecular Dynamics simulations. Preliminary data Our results highlight a progressive elongation of the oligorotaxane structure with increasing charge numbers until it reaches a maximum extension state. Matching the experimental data with theoretical simulations, we find that the oligorotaxanes adopt an entropically-favored globular shape at low z. As z increases, coulombic repulsions occurring between the cyclophanes gradually outweigh the stabilizing π-stacking interactions and force the structure to elongate. This process occurs in a multistep fashion, each corresponding to a distinct group of helical-shaped conformers, before it eventually results in a fully stretched structure. On the other hand, our results also highlight that a charge reduction driven by a non-dissociative electron transfer process leads to a refolding of the structure so that it adopts a size similar to its electrospray-generated counterpart when the appropriate number of electrons is added. This observation may be imparted to the gradual decrease of the Coulomb repulsions between the cyclophanes mediated through increasing numbers of transferred electrons. These results suggests that the transition from one conformer to another is reversible so that the electrostatic balance between the cyclophanes may be used to further tune the structural state adopted by this artificial molecular switch. The second stimulus relied on collisional activation whose inelastic component provides a way to build up energy into the accessible vibrational degrees of freedom. The conformational landscapes of such-activated oligorotaxanes ions were found unchanged in term of collision cross section position but the repartition of population was altered with a promotion of the most elongated conformer, provided the absence of selective fragmentation. Altogether, these results highlight the feasibility of handling the elongation state of oligorotaxanes in the gas phase through appropriate inputs and underline its conformational reversibility properties. Novel aspect Stimuli-induced reversible conformational rearrangements of innovative AMMs studied by IM-MS and molecular dynamics in the gas phase. [less ▲]

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See detailThe Role of Super-Atom Molecular Orbitals in Doped Fullerenes in a Femtosecond Intense Laser Field
Xiong, Hui; Mignolet, Benoît ULiege; Fang, Li et al

in Scientific Reports (2017), 7

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See detailModeling the photoexcitation and photochemistry of H2CSO sulfine
Mignolet, Benoît ULiege

Conference (2017)

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See detailOptical activity of the super-atom molecular orbital (SAMO) states in Li@C60+ conformers
Mignolet, Benoît ULiege; Campbell, Eleanor; Remacle, Françoise ULiege

in AIP Conference Proceedings (2017)

Super Atom Molecular Orbitals (SAMOs) are electronic excited states found in fullerenes in which an electron is excited to one or, more generally, several virtual orbitals with hydrogen like character ... [more ▼]

Super Atom Molecular Orbitals (SAMOs) are electronic excited states found in fullerenes in which an electron is excited to one or, more generally, several virtual orbitals with hydrogen like character. The photoexcitation mechanism of the SAMO states strongly depends on the symmetry of the fullerene. For instance the SAMOs of the spherical C60 fullerene are not optically active while breaking the symmetry by adding a dopant can make the SAMO states optically active. In this proceeding we investigate the optical activity of the SAMO states in several conformers of the Li@C60+ fullerene and we show that the position of the lithium atom inside the fullerene cage strongly affects the computed oscillator strengths and transition dipole moments of the SAMO states. [less ▲]

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See detailUltrafast 25-fs relaxation in highly excited states of methyl azide mediated by strong nonadiabatic coupling
Peters, William K.; Couch, David E.; Mignolet, Benoît ULiege et al

in Proceedings of the National Academy of Sciences of the United States of America (2017)

Highly excited states of neutral molecules behave qualitatively differently than the lower excited states that are commonly studied in photochemistry. Such states are involved in ionospheric and ... [more ▼]

Highly excited states of neutral molecules behave qualitatively differently than the lower excited states that are commonly studied in photochemistry. Such states are involved in ionospheric and astrochemical phenomena, as well as in detonation processes. However, highly excited states are poorly understood due to experimental and theoretical challenges in probing their complex dynamics. Here, we apply vacuum-UV femtosecond laser sources and an imaging photoelectron–photoion coincidence spectrometer to directly probe the surprisingly fast 25-fs reaction pathway of the energetic molecule methyl azide. Combined with advanced calculations, we conclude that the electronic relaxation is driven by strong nonadiabatic coupling and that population transfer occurs along a seam well above the minimum energy conical intersection. [less ▲]

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See detailLow-lying, Rydberg states of polycyclic aromatic hydrocarbons (PAHs) and cyclic alkanes
Bohl, E.; Mignolet, Benoît ULiege; Johansson, J. O. et al

in Physical Chemistry Chemical Physics [=PCCP] (2017), 19(35), 24090-24099

TD-DFT calculations of low-lying, Rydberg states of a series of polycyclic hydrocarbons and cyclic alkanes are presented. Systematic variations in binding energies and photoelectron angular distributions ... [more ▼]

TD-DFT calculations of low-lying, Rydberg states of a series of polycyclic hydrocarbons and cyclic alkanes are presented. Systematic variations in binding energies and photoelectron angular distributions for the first members of the s, p and d Rydberg series are predicted for increasing molecular complexity. Calculated binding energies are found to be in very good agreement with literature values where they exist for comparison. Experimental angle-resolved photoelectron spectroscopy results are presented for coronene, again showing very good agreement with theoretical predictions of binding energies and also for photoelectron angular distributions. The Dyson orbitals for the small "hollow" carbon structures, cubane, adamantane and dodecahedrane, are shown to have close similarities to atomic s, p and d orbitals, similar to the superatom molecular orbitals (SAMOs) reported for fullerenes, indicating that these low-lying, diffuse states are not restricted to π-conjugated molecules. © 2017 the Owner Societies. [less ▲]

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See detailPumping and probing vibrational modulated coupled electronic coherence in HCN using short UV fs laser pulses: A 2D quantum nuclear dynamical study
van den Wildenberg, Stéphan ULiege; Mignolet, Benoît ULiege; Levine, R. D. et al

in Physical Chemistry Chemical Physics [=PCCP] (2017), 19(30), 19837-19846

The coupled electronic-nuclear coherent dynamics induced by a short strong VUV fs pulse in the low excited electronic states of HCN is probed by transient absorption spectroscopy with a second weaker fs ... [more ▼]

The coupled electronic-nuclear coherent dynamics induced by a short strong VUV fs pulse in the low excited electronic states of HCN is probed by transient absorption spectroscopy with a second weaker fs UV pulse. The nuclear time-dependent Schrodinger equation is solved on a 2D nuclear grid with several electronic states with a Hamiltonian including the dipole coupling to the pump and the probe electric fields. The two internal nuclear coordinates describe the motion of the light H atom. There is a band of several excited electronic states at about 8 eV above the ground state (GS) that is transiently accessed by the pump pulse. We tailored the pump so as to selectively populate the lowest 1A′′ electronic state thereby the pulse creates an electronic coherence with the GS. Our simulations show that this electronic coherence is modulated by the nuclear motion and persists all the way to dissociation on the 1A′′ state. Transient absorption spectra computed as a function of the delay time between the pump and the probe pulses provide a detailed probe of the electronic amplitude and its phase, as well as of the modulation of the electronic coherence by the nuclear motion, both bound and dissociative. © the Owner Societies 2017. [less ▲]

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See detailA new electron-ion coincidence 3D momentum-imaging method and its application in probing strong field dynamics of 2-phenylethyl-N, N-dimethylamine
Fan, Lin; Lee, Suk Kyoung; Tu, Yi-Jung et al

in Journal of Chemical Physics (2017), 147

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See detailNuclear Motion Driven Ultrafast Photodissociative Charge Transfer of the PENNA Cation: An Experimental and Computational Study
Sun, Shoutian; Mignolet, Benoît ULiege; Fan, lin et al

in Journal of Physical Chemistry A (2017), 121(7), 1442

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See detailRich Athermal Ground‐State Chemistry Triggered by Dynamics through a Conical Intersection
Mignolet, Benoît ULiege; Curchod, Basile; Martínez, Todd J.

in Angewandte Chemie International Edition (2016), 128(48), 15217-15220

A fundamental tenet of statistical rate theories (such as transition state theory and RRKM) is the rapidity of vibrational relaxation. Excited-state reactions happen quite quickly (sub-picosecond) and ... [more ▼]

A fundamental tenet of statistical rate theories (such as transition state theory and RRKM) is the rapidity of vibrational relaxation. Excited-state reactions happen quite quickly (sub-picosecond) and thus can exhibit nonstatistical behavior. However, it is often thought that any diversity of photoproducts results from different conical intersections connecting the excited and ground electronic states. It is also conceivable that the large energy of the photon, which is converted to vibrational energy after electronic transitions could lead to athermal hot ground state reactions and that these might be responsible for the diversity of photoproducts. Here we show that this is the case for sulfines, where a single conical intersection is implicated in the electronic transition but the excited state reaction leads to nine different products within less than a picosecond. [less ▲]

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See detailUltrafast molecular dynamics induced by attopulses
Mignolet, Benoît ULiege

Conference (2016)

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