Peer-reviewed Publications |
Alata, I., Scuderi, D., Lepere, V., Steinmetz, V., Gobert, F., Thiao-Layel, L., Le Barbu-Debus, K., & Zehnacker-Rentien, A. (2015). Exotic Protonated Species Produced by UV-Induced Photofragmentation of a Protonated Dimer: Metastable Protonated Cinchonidine. Journal Of Physical Chemistry A, 119(39), 10007–10015.
Résumé: A metastable protonated cinchona alkaloid was produced in the gas phase by UV-induced photodissociation (UVPD) of its protonated dimer in a Paul ion trap. The infrared multiple photon dissociation (IRMPD) spectrum of the molecular ion formed by UVPD was obtained and compared to DFT calculations to characterize its structure. The protonation site obtained thereby is not accessible by classical protonation ways. The protonated monomer directly formed in the ESI source or by collision-induced dissociation (CID) of the dimer undergoes protonation at the most basic alkaloid nitrogen. In contrast, protonation occurs at the quinoline aromatic ring nitrogen in the UVPD-formed monomer.
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Alauddin, M., Gloaguen, E., Brenner, V., Tardivel, B., Mons, M., Zehnacker-Rentien, A., Declerck, V., & Aitken, D. J. (2015). Intrinsic Folding Proclivities in Cyclic β-Peptide Building Blocks: Configuration and Heteroatom Effects Analyzed by Conformer-Selective Spectroscopy and Quantum Chemistry. Chem. Eur. J., 21(46), 16479–16493.
Résumé: This work describes the use of conformer-selective laser spectroscopy following supersonic expansion to probe the local folding proclivities of four-membered ring cyclic β-amino acid building blocks. Emphasis is placed on stereochemical effects as well as on the structural changes induced by the replacement of a carbon atom of the cycle by a nitrogen atom. The amide A IR spectra are obtained and interpreted with the help of quantum chemistry structure calculations. Results provide evidence that the building block with a trans-substituted cyclobutane ring has a predilection to form strong C8 hydrogen bonds. Nitrogen-atom substitution in the ring induces the formation of the hydrazino turn, with a related but distinct hydrogen-bonding network: the structure is best viewed as a bifurcated C8/C5 bond with the N heteroatom lone electron pair playing a significant acceptor role, which supports recent observations on the hydrazino turn structure in solution. Surprisingly, this study shows that the cis-substituted cyclobutane ring derivative also gives rise predominantly to a C8 hydrogen bond, although weaker than in the two former cases, a feature that is not often encountered for this building block.
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Arabei, S., McCaffrey, J. G., Galaup, J. - P., Shafizadeh, N., & Crepin, C. (2015). Stimulated emission in cryogenic samples doped with free-base tetraazaporphine. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 17(22), 14931–42.
Résumé: Thin cryogenic samples of inert gas solids doped with free-base tetraazaporphine (H2TAP) were irradiated with a tunable pulsed laser. Under resonant electronic excitation of the guest, specific vibronic transitions of the fluorescence spectra were found to be strongly enhanced with only a moderate increase of the laser power. This enhancement is due to stimulated emission (SE). The characteristics of SE bands are described in the three hosts (Ar, N2, and Ne) explored, as well as their excitation spectra. SE is observed in transitions involving different vibrational modes of the guest, depending on the host and the electronic excitation. The results are discussed in comparison with previous works on other tetrapyrrolic molecules trapped in inert gas matrices. From this comparison the key features required to observe SE are deduced to be: (1) SE can be obtained with various tetrapyrrolic molecules; (2) free-base molecules are preferable to their metallo-counterparts; (3) the results highlight a specific molecular vibrational mode involved in the process; and (4) cryogenic crystal structures are also of importance in the detection of SE.
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Bouchet, A., Klyne, J., Piani, G., Dopfer, O., & Zehnacker, A. (2015). Diastereo-specific conformational properties of neutral, protonated and radical cation forms of (1R,2S)-cis- and (1R,2R)-trans-amino-indanol by gas phase spectroscopy. Physical Chemistry Chemical Physics, 17(39), 25809–25821.
Résumé: Chirality effects on the intramolecular interactions strongly depend on the charge and protonation states. Here, the influence of chirality on the structure of the neutral, protonated, and radical cation forms of (1R,2S)-cis- and (1R,2R)-trans-1-amino-2-indanol diastereomers, prototypical molecules with two chiral centers, is investigated in a molecular beam by laser spectroscopy coupled with quantum chemical calculations. The neutral systems are structurally characterised by double resonance IR-UV spectroscopy, while IR-induced dissociation spectroscopy is employed for the charged molecules. The sterical constraints due to the cyclic nature of the molecule emphasise the chirality effects, which manifest themselves by the formation of an intramolecular hydrogen bond in neutral or protonated (1R,2S)-cis-amino-indanol. In contrast, this interaction is not possible in (1R,2R)-trans-amino-indanol. In the protonated species, chirality also influences the spectroscopic probes in the NH/OH stretch range by fine-tuning subtle effects such as the hyperconjugation between the sigma(OH) orbital and sigma* orbitals localised on the alicyclic ring. The radical cation undergoes opening of the alicyclic ring, which results in an ionisation-induced loss of the chirality effects.
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Broquier, M., Soorkia, S., & Gregoire, G. (2015). A comprehensive study of cold protonated tyramine: UV photodissociation experiments and ab initio calculations. Phys Chem Chem Phys, 17, 25854–25862.
Résumé: We present a comprehensive experimental study of protonated tyramine ions in a cold 3D quadrupole ion trap coupled to a time-of-flight mass spectrometer. Multiple UV photodissociation techniques have been developed, including single and double resonance spectroscopy along with time-resolved excited state lifetime measurements through a picosecond pump-probe scheme. An original UV-UV hole burning method is presented which can be used without modification of the quadrupole ion trap. The electronic spectrum of the cold protonated tyramine exhibits well-defined vibronic transitions, allowing the firm assignment of its two low-lying energy conformations by comparison with CC2 ab initio excited state calculations.
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Douin, S., Gronowski, M., Lamarre, N., Phung, V. - T., Boyé-Péronne, S., Crépin, C., & and Kołos, R. (2015). Cavity Ring Down Spectroscopy Measurements for High-Overtone Vibrational Bands of HC3N. Journal of Physical Chemistry A, 119(36), 9494–9505.
Résumé: Overtone (5ν1 and 6ν1) and combination (4ν1+ν3 and 4ν1+ν2) vibrational bands of gaseous HC3N, located in the visible range (14 600-15 800 cm-1 and 17 400-18 600 cm-1), were investigated by cavity ring-down absorption spectroscopy. The 5ν1+ν3 and 5ν1+ν2 combinations as well as the 6ν1+ν5-ν5 hot overtone band have also been identified, based on previous overtone assignments. Absolute integrated intensity values and the ensuing oscillator strengths have been measured here for the first time; f –values are typically confined between 4×10-12 and 7×10-11. For the even weaker 5ν1+ν2 combination band, the oscillator strength was estimated as 9×10-13.
The values concerning CH-stretch overtones (nν1) are similar to those found in the literature for HCN and C2H2, the molecules with sp-hybridized carbon atoms. Data presented here may prove useful for studying the photochemistry triggered with visible or near-IR radiation within the atmospheres of certain Solar System bodies, including Titan.
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Feraud, G., Broquier, M., Dedonder, C., Jouvet, C., Gregoire, G., & Soorkia, S. (2015). Excited State Dynamics of Protonated Phenylalanine and Tyrosine: Photo-Induced Reactions Following Electronic Excitation. J Phys Chem A, 119(23), 5914–5924.
Résumé: The electronic spectroscopy and the electronic excited state properties of cold protonated phenylalanine and protonated tyrosine have been revisited on a large spectral domain and interpreted by comparison with ab initio calculations. The protonated species are stored in a cryogenically cooled Paul trap, maintained at approximately 10 K, and the parent and all the photofragment ions are mass-analyzed in a time-of-flight mass spectrometer, which allows detecting the ionic species with an improved mass resolution compared to what is routinely achieved with a quadrupole mass spectrometer. These new results emphasize the competition around the band origin between two proton transfer reactions from the ammonium group toward either the aromatic chromophore or the carboxylic acid group. These reactions are initiated by the coupling of the locally excited pipi* state with higher charge transfer states, the positions and coupling of which depend on the conformation of the protonated molecules. Each of these reaction processes gives rise to specific fragmentation channels that supports the conformer selectivity observed in the photofragmentation spectra of protonated tyrosine and phenylalanine.
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Ferrand, L., Soorkia, S., Gregoire, G., Broquier, M., Soep, B., & Shafizadeh, N. (2015). Bonding of heme FeIIIwith dioxygen: Observation and characterization of an incipient bond. Phys. Chem. Chem. Phys., 17, 25693–25699.
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Hernandez, F. J., Capello, M. C., Naito, A., Manita, S., Tsukada, K., Miyazaki, M., Fujii, M., Broquier, M., Gregoire, G., Dedonder-Lardeux, C., Jouvet, C., & Pino, G. A. (2015). Trapped Hydronium Radical Produced by Ultraviolet Excitation of Substituted Aromatic Molecule. J Phys Chem A, 119(51), 12730–12735.
Résumé: The gas phase structure and excited state dynamics of o-aminophenol-H2O complex have been investigated using REMPI, IR-UV hole-burning spectroscopy, and pump-probe experiments with picoseconds laser pulses. The IR-UV spectroscopy indicates that the isomer responsible for the excitation spectrum corresponds to an orientation of the OH bond away from the NH2 group. The water molecule acts as H-bond acceptor of the OH group of the chromophore. The complexation of o-aminophenol with one water molecule induced an enhancement in the excited state lifetime on the band origin. The variation of the excited state lifetime of the complex with the excess energy from 1.4 +/- 0.1 ns for the 0-0 band to 0.24 +/- 0.3 ns for the band at 0-0 + 120 cm(-1) is very similar to the variation observed in the phenol-NH3 system. This experimental result suggests that the excited state hydrogen transfer reaction is the dominant channel for the non radiative pathway. Indeed, excited state ab initio calculations demonstrate that H transfer leading to the formation of the H3O(*) radical within the complex is the main reactive pathway.
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Lamarre, N., Gans, B., Alcaraz, C., Cunha de Miranda, B., Guillemin, J. - C., Broquier, M., Liévin, J., & Boyé-Péronne, S. (2015). Vibronic structure of the 2Πu ground electronic state of dicyanoacetylene cation revisited by PFI-ZEKE photoelectron spectroscopy and ab initio calculations. Molecular Physics, 113(24), 3946–3954.
Résumé: The X+ 2Piu ← X 1Sigma+ g transition of dicyanoacetylene has been recorded for the first time using Pulsed-Field-Ionization ZEro-Kinetic Energy (PFI-ZEKE) photoelectron spectroscopy.
The analysis of the photoelectron spectrum allowed an accurate determination of the adiabatic ionization potential of C4N2 (Ei, ad./hc = 95479±2 cm−1) and a description of the vibrational structure of the electronic ground state of the cation which is affected by Renner-Teller effect and spin-orbit interaction. The spin-orbit coupling constant was measured as −52 ± 2 cm−1.
These results are supported by ab initio calculations performed at the Complete Active Space Self Consistent Field and Second order Perturbation Theory (CASSCF and CASPT2) levels of theory, with extrapolation to the complete basis set limit.
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Lozada-Garcia, R., Rojas-Lorenzo, G., Crepin, C., Ryan, M., & McCaffrey, J. G. (2015). Hg-Xe Exciplex Formation in Mixed Xe/Ar Matrices: Molecular Dynamics and Luminescence Study. Journal Of Physical Chemistry A, 119(11), 2307–2317.
Résumé: Luminescence of Hg(P-3(1)) atoms trapped in mixed Ar/Xe matrices containing a small amount of Xe is reported. Broad emission bands, strongly red-shifted from absorption are recorded which are assigned to strong complexes formed between the excited mercury Hg* and xenon atoms. Molecular dynamics calculations are performed on simulated Xe/Ar samples doped with Hg to follow the behavior of Hg* in the mixed rare gas matrices leading to exciplex formation. The role of Xe atoms in the first solvation shell (SS1) around Hg was investigated in detail, revealing the formation of two kinds of triatomic exciplexes; namely, Xe-Hg*-Xe and Ar-Hg*-Xe. The first species exists only when two xenon atoms are present in SS1 with specific geometries allowing the formation of a linear or quasi-linear exciplex. In the other geometries, or in the presence of only one Xe in SS1, a linear Ar-Hg*-Xe exciplex is formed. The two kinds of exciplexes have different emission bands, the most red-shifted being that involving two Xe atoms, whose emission is very close to that observed in pure Xe matrices. Simulations give a direct access to the analysis of the experimental absorption, emission, and excitation spectra, together with the dynamics of exciplexes formation.
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Mengesha, E. T., Zehnacker-Rentien, A., Sepiol, J., Kijak, M., & Waluk, J. (2015). Spectroscopic Study of Jet-Cooled Deuterated Porphycenes: Unusual Isotopic Effects on Proton Tunneling. J. Phys. Chem. B, 119(6), 2193–2203.
Résumé: Porphycene (Pc) is a well-known model for studying double hydrogen transfer, which shows vibrational-mode-specific tunneling splitting when isolated in supersonic jets or helium nanodroplets. The effect of deuteration on tunneling splitting is reported for jet-cooled heterogeneous, deuterated Pc samples (Pc-d(mix)) with the prevailing contribution of Pc-d(12) isotopologue. The sample introduced into the gas phase using laser desorption is studied by means of laser-induced fluorescence (LIF) and single vibronic level fluorescence (SVLF) measurements, in combination with quantum chemical calculations. The influence of molecular symmetry is studied by comparing Pc, Pc-d(12), and Pc-d(11). The spectra of Pc-d(12) show strong similarity to those of the parent undeuterated porphycene (Pc). Comparable tunneling splitting is observed in the two isotopologues, both for the 00 transition and the most efficient promoting 2A(g) mode. In contrast, an unusual isotopic effect is observed for the totally symmetrical 4A(g) mode. While this vibration behaves as a neutral mode in Pc, neither enhancing nor decreasing the tunneling efficiency, it strongly promotes hydrogen transfer in Pc-d(12). This observation is explained in terms of modification of the displacement vectors of the 4A(g) mode upon deuteration. It demonstrates that isotope substitution affects hydrogen transfer even when the weak structural modifications are far from the reaction center, emphasizing the strongly multidimensional nature of the tunneling process.
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Soorkia, S., Dehon, C., S, S. K., Perot-Taillandier, M., Lucas, B., Jouvet, C., Barat, M., & Fayeton, J. A. (2015). Ion-Induced Dipole Interactions and Fragmentation Times: Calpha-Cbeta Chromophore Bond Dissociation Channel. J Phys Chem Lett, 6(11), 2070–2074.
Résumé: The fragmentation times corresponding to the loss of the chromophore (Calpha-Cbeta bond dissociation channel) after photoexcitation at 263 nm have been investigated for several small peptides containing tryptophan or tyrosine. For tryptophan-containing peptides, the aromatic chromophore is lost as an ionic fragment (m/z 130), and the fragmentation time increases with the mass of the neutral fragment. In contrast, for tyrosine-containing peptides the aromatic chromophore is always lost as a neutral fragment (mass = 107 amu) and the fragmentation time is found to be fast (<20 ns). These different behaviors are explained by the role of the postfragmentation interaction in the complex formed after the Calpha-Cbeta bond cleavage.
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Spagnoli, S., Morfin, I., Gonzalez, M. A., Carcabal, P., & Plazanet, M. (2015). Solvent Contribution to the Stability of a Physical Gel Characterized by Quasi-Elastic Neutron Scattering. Langmuir, 31(8), 2554–2560.
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Turowski, M., Crepin, C., Douin, S., & Kolos, R. (2015). Formation and Spectroscopy of Dicyanotriacetylene (NC8N) in Solid Kr. Journal Of Physical Chemistry A, 119(11), 2701–2708.
Résumé: Thermally induced creation of dicyanotriacetylene (NC8N) was observed in solid krypton. Samples were obtained by cryogenic trapping of gaseous cyanoacetylene/Kr mixtures subjected to electric discharges. Strong a (3)Sigma(+)(u) -> X (1)Sigma(+)(g) phosphorescence of NC8N is reported here for the first time; its vibronic structure permitted the measurement of several ground-state vibrational frequencies. Other chemical species, mostly smaller than the precursor molecule, have also been formed, among them the dicarbon molecule (C-2), and these may serve as indispensable building blocks in the NC8N synthesis. Processes leading to the elongation of cyanoacetylenic chains are of potential importance for the chemistry of icy grains present in the interstellar gas clouds.
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Zehnacker, A. (2015). Optical spectroscopy coupled with mass spectrometry methods. Physical Chemistry Chemical Physics, 17(39), 25672–25675.
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Procédures de Conférences |
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Briant, M., Poisson, L., Shafizadeh, N., & Soep, B. (2015). Tribute to Jean-Michel Mestdagh (Vol. 119). American Chemical Society.
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Chapitres de Livres |
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Cocinero, E. J., & Carcabal, P. (2015). Carbohydrates. In Gas-Phase Ir Spectroscopy And Structure Of Biological Molecules (Vol. 364, pp. 299–333).
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