Peer-reviewed Publications |
Alata, I., Dedonder, C., Broquier, M., Marceca, E., & Jouvet, C. (2010). Role of the charge-transfer state in the electronic absorption of protonated hydrocarbon molecules. J Am Chem Soc, 132(49), 17483–17489.
Résumé: The vibrationally resolved electronic spectra of isolated protonated polycyclic aromatic hydrocarbons (PAHs)-naphthalene, anthracene, and tetracene-have been recorded via neutral photofragment spectroscopy. The S1<--S0 transitions are all in the visible region and do not show a monotonic red shift as a function of the molecular size, as observed for the neutral analogues. Comparison with ab initio calculations indicates that this behavior is due to the nature of the excited state, which has a pronounced charge-transfer character for protonated linear PAHs with an even number of aromatic rings.
|
|
Alata, I., Omidyan, R., Broquier, M., Dedonder, C., Dopfer, O., & Jouvet, C. (2010). Effect of protonation on the electronic structure of aromatic molecules: naphthaleneH+. Phys Chem Chem Phys, 12(43), 14456–14458.
Résumé: Protonated naphthalene, the smallest protonated polycyclic aromatic hydrocarbon cation, absorbs in the visible, around 500 nm, which corresponds to an unusually large red shift with respect to the neutral naphthalene counterpart.
|
|
Albrecht, M., Borba, A., Le Barbu-Debus, K., Dittrich, B., Fausto, R., Grimme, S., Mahjoub, A., Nedic, M., Schmitt, U., Schrader, L., Suhm, M. A., Zehnacker-Rentien, A., & Zischang, J. (2010). Chirality influence on the aggregation of methyl mandelate. NEW JOURNAL OF CHEMISTRY, 34(7), 1266–1285.
Résumé: The methyl ester of mandelic acid is investigated by a wide range of techniques to unravel its aggregation pattern and the influence of relative chirality of the aggregating monomers. Matrix isolation confirms that a single monomer conformation prevails. The electronic spectrum of the dimers is strongly affected by the relative monomer chirality. Vibrational effects are more subtle and can be explained in terms of the most stable homo- and heteroconfigurational dimer structures, when compared to results of MP2 and DFT-D computations. Selective IR/UV double resonance techniques and wide-band FTIR spectroscopy provide largely consistent spectroscopic fingerprints of the chirality discrimination phenomena. The dominant homochiral dimer has two intermolecular O-H center dot center dot center dot O=C hydrogen bonds whereas the more strongly bound heterochiral dimer involves only one such hydrogen bond. This is a consequence of the competition between dispersion and intramolecular or intermolecular hydrogen bonding. Aromatic interactions also play a role in trimers and larger clusters, favoring homochiral ring arrangements. Analogies and differences to the well-investigated methyl lactate system are highlighted. Bulk phases show a competition between different hydrogen bond patterns. The enantiopure, racemic, and 3 : 1 crystals involve infinite hydrogen-bonded chains with different arrangements of the aromatic groups. They exhibit significantly different volatility, the enantiopure compound being more volatile than the racemic crystal. The accumulated experimental and quantum-chemical evidence turns methyl mandelate into a model system for the role of competition between dispersion forces and hydrogen bond interactions in chirality discrimination.
|
|
Albrieux, F., Calvo, F., Chirot, F., Vorobyev, A., Tsybin, Y. O., Lepere, V., Antoine, R., Lemoine, J., & Dugourd, P. (2010). Conformation of Polyalanine and Polyglycine Dications in the Gas Phase: Insight from Ion Mobility Spectrometry and Replica-Exchange Molecular Dynamics. JOURNAL OF PHYSICAL CHEMISTRY A, 114(25), 6888–6896.
Résumé: The conformation of model [Arg(Ala)(4)X(Ala)(4)Lys+2H](2+) and [Arg(Gly)(4)X(Gly)(4)Lys+2H](2+) peptides has been systematically investigated as a function of the central amino acid X through a combined experimental and theoretical approach. Mass spectrometry-based ion mobility measurements have been performed together with conformational sampling using replica-exchange molecular dynamics to probe the influence of each amino acid on the stable peptide conformation. Satisfactory agreement is obtained between measured and calculated diffusion cross section distributions. The results confirm the propensity of alanine-based peptides to form a-helices in the gas phase, differences between peptides arising from the local arrangement of the central side chain with respect to the charged ends. More generally, we find that charge solvation plays a major role in secondary structure stabilization, especially in the case of glycine-based peptides. The rich variety of conformations exhibited by the latter is qualitatively captured by the simulations. This work illustrates the potentiality of such combined experimental/theoretical strategy to determine peptide secondary structures. The present polyalanine and polyglycine peptides also offer a series of benchmark systems for future conformation-resolved studies.
|
|
|
Anne Zehnacker Ed. (2010). Chiral Recognition in the Gas Phase. CRC Press Taylor & Francis Group, .
|
|
Ceponkus, J., Chin, W., Chevalier, M., Broquier, M., Limongi, A., & Crepin, C. (2010). Infrared study of glycolaldehyde isolated in parahydrogen matrix. JOURNAL OF CHEMICAL PHYSICS, 133(9), 094502.
Résumé: The infrared spectrum of glycolaldehyde sugar model in solid parahydrogen is reported and interpreted in the light of ab initio anharmonic frequency calculations. The advantages of parahydrogen lead to a simplification of its infrared spectroscopy compared to other conventional matrices. Surprisingly, the sugar molecule is found to display an unexpected large bandwidth compared to the smaller organic molecules studied in parahydrogen so far. Among them, only glycolaldehyde possesses an internal hydrogen-bond. Band broadening in glycolaldehyde is interpreted as originating mainly from the presence of the hydrogen-bond and to a lesser extent from clustering with oH(2) impurities. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3474994]
|
|
Chakraborty, A., Le Barbu-Debus, K., Zehnacker-Rentien, A., & Guchhait, N. (2010). Laser-induced fluorescence and dispersed fluorescence studies of the donor-acceptor system 4-amino 3-methyl benzoic acid methyl ester and its solvated clusters: Evidence of excited-state charge-transfer reaction. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY, 213(2-3), 164–170.
Résumé: Laser-induced fluorescence (LIF) excitation and dispersed fluorescence (OF) spectra of 4-amino 3-methyl benzoic acid methyl ester (AMBME) and its solvated clusters with solvents such as methanol, water and acetonitrile have been investigated in a supersonic expansion. Spectral signature supports the presence of two conformers in the cooled jet which is in line with theoretical calculations. In addition to structured local emission from the Franck Condon excited state, the molecule AMBME shows red-shifted broad emission from the state attributed to the close-lying charge transfer (CT) state, which is facilitated by exciting low-frequency modes. The molecule readily forms clusters with different solvents and the clusters' electronic excitation bands appear in the low-energy side of the transition origin of the bare molecule. Excitation of the clusters leads to the appearance of red-shifted solvent-polarity dependent CT emission. (C) 2010 Elsevier B.V. All rights reserved.
|
|
Champeaux, J. P., Carcabal, P., Rabier, J., Cafarelli, P., Sence, M., & Moretto-Capelle, P. (2010). Dehalogenation of 5-halo-uracil molecules induced by 100 keV proton collisions. Phys. Chem. Chem. Phys., 12(20), 5454–5461.
Résumé: Neutral and cationic halogen loss of singly and doubly ionised 5-X-uracil (X = F, Cl, Br, I) after collisions with 100 keV protons have been studied in the gas phase. The rates of these dissociation channels are strongly dependant on the nature of the halogen substituent. It is very weak in the case of fluorine but is a dominant channel for iodine. Dissociation mechanisms are proposed for a number of significant channels associated to dehalogenation. It is suggested that some final ion products originate from specific processes. For instance, ion products of mass 38, 39 and 40 amu are very sensitive to the nature of the primarily ejected halogen and result from pathways associated to dehydrogenation and transient formation of the dehalogenated uracil cation.
|
|
Chevalier, M., Broquier, M., & Brenner, V. (2010). Infrared study on hydrogen chloride complexed with allene. J. Chem. Phys., 132(16), 164306.
Résumé: The first rotationally resolved observation of the infrared (IR) spectrum of the molecular complex C(3)H(4)-HCl in gas phase is reported. New IR spectra have been recorded at high resolution by means of a slit jet. Rotational constants and vibrational frequencies have been obtained from these spectra. These data are presented and compared with high level ab initio calculations (CCSD(T)/cc-pVTZ). The results obtained in this study are compared with those on acetylene and ethene-HCl complexes. We observe a broadening of the lines interpreted as a decrease of the lifetime of the excited vibrational state with the size of the partner of complexation and also a correlation between the vibrational shift of the H-Cl stretching mode and the proton affinity of the acceptor molecule. (C) 2010 American Institute of Physics. [doi:10.1063/1.3397990]
|
|
|
Crepin C., S. N., Chin W., Galaup J.P., M. C. J. G., & Arabei S.M. (2010). Emission stimulée par des molécules de tétrabenzoporphine en matrice de gaz rares à basse température. PROCEEDINGS of the VIII International Conference on “Quantum Electronics”, (Minsk, Belarus), 57.
|
|
Crepin, C., Shafizadeh, N., Chin, W., Galaup, J. - P., McCaffrey, J. G., & Arabei, S. M. (2010). Unveiled optical properties of tetrapyrollic pigments in cryogenic environments. LOW TEMPERATURE PHYSICS, 36(5), 451–457.
Résumé: An unexpected phenomenon was revealed in the laser induced fluorescence spectra of free-base (H(2)Pc) and zinc (ZnPc) phthalocyanines trapped in rare gas and nitrogen matrices under a moderate increase in the laser intensity. In all matrices the intensity of an emission band near 755 nm increased drastically when pumping the S(1)<- S(0) transition. This observation was assigned to stimulated emission in a four-level scheme involving a vibronic transition from the lowest electronic state to a vibrational level of the ground state. In the present work, we expose new similar results obtained with porphyrin molecules, i.e. tetra-benzoporphin (TBP). With free-base H(2)TBP, stimulated emission was observed in Ar or N(2) matrices, but not in Xe matrices. A possible reason could be a fast inter-system crossing rate due to the heavy atom effect induced by Xe. We also report the observation of persistent burnt spectral holes, although the low efficiency of this process is not competitive with stimulated emission and no decrease of the stimulated emission with time was observed. With ZnTBP no stimulated emission could be recorded but the appearance of rather strong phosphorescence was noticed. Similar studies focusing on the stimulated emission phenomenon is that they should allow new insights into site effects and site selectivity. (C) 2010 American Institute of Physics.
|
|
Gloaguen, E., de Courcy, B., Piquemal, J. - P., Pilme, J., Parisel, O., Pollet, R., Biswal, H. S., Piuzzi, F., Tardivel, B., Broquier, M., & Mons, M. (2010). Gas-Phase Folding of a Two-Residue Model Peptide Chain: On the Importance of an Interplay between Experiment and Theory. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 132(34), 11860–11863.
Résumé: In order to assess the ability of theory to describe properly the dispersive interactions that are ubiquitous in peptide and protein systems, an isolated short peptide chain has been studied using both gas-phase laser spectroscopy and quantum chemistry. The experimentally observed coexistence of an extended form and a folded form in the supersonic expansion was found to result from comparable Gibbs free energies for the two species under the high-temperature conditions (<= 320 K) resulting from the laser desorption technique used to vaporize the molecules. These data have been compared to results obtained using a series of quantum chemistry methods, including DFT, DFT-D, and post-Hartree-Fock methods, which give rise to a wide range of relative stabilities predicted for these two forms. The experimental observation was best reproduced by an empirically dispersion-corrected functional (B97-D) and a hybrid functional with a significant Hartree-Fock exchange term (M06-2X). In contrast, the popular post-Hartree-Fock method MP2, which is often used for benchmarking these systems, had to be discarded because of a very large basis-set superposition error. The applicability of the atomic counterpoise correction (ACP) is also discussed. This work also introduces the mandatory theoretical examination of experimental abundances. Delta H(0 K) predictions are clearly not sufficient for discussion of folding, as the conformation inversion temperature is crucial to the conformation determination and requires taking into account thermodynamical corrections (Delta G) in order to computationally isolate the most stable conformation.
|
|
Mitsuda, H., Miyazaki, M., Nielsen, I. B., Carcabal, P., Dedonder, C., Jouvet, C., Ishiuchi, S., & Fujii, M. (2010). Evidence for Catechol Ring- Induced Conformational Restriction in Neurotransmitters. J. Phys. Chem. Lett., 1(7), 1130–1133.
Résumé: In the neurotransmission process, a specific neurotransmitter binds to a specific receptor in a “key and lock” recognition process. Neurotransmitters, such as the catecholamines, are flexible molecules that can change their shape easily in principle. However, conformations of both the “key” and “lock” must be quite limited to achieve high selectivity. We have investigated the conformational diversity of catecholamines and related molecules by laser spectroscopy. Molecules of the tyrosine family, which contain a phenolic aromatic chromophore, exist as several conformers. In contrast, a single conformer is observed in dopa and other catecholamines, which contain two hydroxyl groups on the benzene moiety (catechol). This demonstrates that the presence of a catechol ring restricts significantly the number of stable conformations.
|
|
Murray, C., Dozova, N., McCaffrey, J. G., FitzGerald, S., Shafizadeh, N., & Crepin, C. (2010). Infra-red and Raman spectroscopy of free-base and zinc phthalocyanines isolated in matrices. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 12(35), 10406–10422.
Résumé: The infrared absorption spectra of matrix-isolated zinc phthalocyanine (ZnPc) and free-base phthalocyanine (H(2)Pc) have been recorded in the region from 400 to 4000 cm(-1) in solid N(2), Ar, Kr and Xe. Raman spectra have been recorded in doped KBr pellets. The isotopomers HDPc and D(2)Pc have been synthesised in an attempt to resolve the conflicting assignments that currently exist in the literature for the N-H bending modes in H2Pc spectra. A complete correlation between the vibrational modes of the three free-base isotopomers and ZnPc has been achieved. Comparison of the IR and Raman spectroscopic results, obtained with isotopic substitution and with predictions from large basis set ab initio calculations, allows identification of the in-plane (IP) and out-of-plane (OP) N-H bending modes. The largest IP isotope shift is observed in the IR at 1046 cm(-1) and at 1026 cm(-1) in Raman spectra while the largest effect in the OP bending modes is at 764 cm(-1). OP bending modes are too weak to be observed in the experimental Raman data. The antisymmetric N-H stretching mode is observed at similar to 3310 cm(-1) in low temperature solids slightly blue shifted from, but entirely consistent with the literature KBr data. With the exception of the N-H stretches, the recorded H/D isotope shifts in all the N-H vibrations are complex, with the IP bending modes exhibiting small nu H/nu D ratios (the largest value is 1.089) while one of the observed OP modes has a ratio < 1. DFT results reveal that the small ratios arise in particular from strong coupling of the N-H IP bending modes with IP stretching modes of C-N bonds. The unexpected finding of a nu H/nu D ratio smaller than one was analysed theoretically by examining the evolution of the frequencies of the free base by increasing the mass from H to D in a continuous manner. A consequence of this frequency increase in the heavier isotopomer is that the direction of the N-D OP bend is reversed from the N-H OP bend.
|
|
Perot, M., Lucas, B., Barat, M., Fayeton, J. A., & Jouvet, C. (2010). Mechanisms of UV Photodissociation of Small Protonated Peptides. JOURNAL OF PHYSICAL CHEMISTRY A, 114(9), 3147–3156.
Résumé: Photofragmentation of protonated dipeptides by 263 nm photons is Investigated with,ill experimental technique based oil the detection in coincidence of the ionic and neutral fragments. With this method, it is possible to determine whether the fragmentation takes, place in one or several steps The timing of these steps call also be evaluated The interpretation of the various fragmentation pathways is tentatively developed along the same line IS that previously proposed for tryptophan The fragmentation call be explained by two types of mechanisms internal conversions and direct fragmentations triggered by the migration of the photoactive electron oil positive charged sties or oil oxygen sites
|
|
Perot, M., Lucas, B., Barat, M., Fayeton, J. A., & Jouvet, C. (2010). Mechanisms of UV photodissociation of small protonated peptides. J Phys Chem A, 114(9), 3147–3156.
Résumé: Photofragmentation of protonated dipeptides by 263 nm photons is investigated with an experimental technique based on the detection in coincidence of the ionic and neutral fragments. With this method, it is possible to determine whether the fragmentation takes place in one or several steps. The timing of these steps can also be evaluated. The interpretation of the various fragmentation pathways is tentatively developed along the same line as that previously proposed for tryptophan. The fragmentation can be explained by two types of mechanisms: internal conversions and direct fragmentations triggered by the migration of the photoactive electron on positive charged sites or on oxygen sites.
|
|
Pino, G. A., Oldani, A. N., Marceca, E., Fujii, M., Ishiuchi, S. - I., Miyazaki, M., Broquier, M., Dedonder, C., & Jouvet, C. (2010). Excited state hydrogen transfer dynamics in substituted phenols and their complexes with ammonia: pi pi*-pi sigma* energy gap propensity and ortho-substitution effect. JOURNAL OF CHEMICAL PHYSICS, 133(12), 124313.
Résumé: Lifetimes of the first electronic excited state (S(1)) of fluorine and methyl (o-, m-, and p-) substituted phenols and their complexes with one ammonia molecule have been measured for the 00 transition and for the intermolecular stretching sigma(1) levels in complexes using picosecond pump-probe spectroscopy. Excitation energies to the S(1) (pi pi*) and S(2) (pi sigma*) states are obtained by quantum chemical calculations at the MP2 and CC2 level using the aug-cc-pVDZ basis set for the ground-state and the S(1) optimized geometries. The observed lifetimes and the energy gaps between the (pi pi*) and (pi sigma*) states show a good correlation, the lifetime being shorter for a smaller energy gap. This propensity suggests that the major dynamics in the excited state concerns an excited state hydrogen detachment or transfer (ESHD/T) promoted directly by a S(1)/S(2) conical intersection, rather than via internal conversion to the ground-state. A specific shortening of lifetime is found in the o- fluorophenol-ammonia complex and explained in terms of the vibronic coupling between the pi pi* and pi sigma* states occurring through the out-of-plane distortion of the C-F bond. (C) 2010 American Institute of Physics. [doi:10.1063/1.3480396]
|
|
Ryan, M., Collier, M., de Pujo, P., Crepin, C., & McCaffrey, J. G. (2010). Investigations of the Optical Spectroscopy of Atomic Sodium Isolated in Solid Argon and Krypton: Experiments and Simulations. JOURNAL OF PHYSICAL CHEMISTRY A, 114(9), 3011–3024.
Résumé: The absorption spectra of thin film samples. formed by (lie codeposition of sodium vapor with the rare gases have long been known to consist of complex structures in the region of the atomic sodium “yellow-doublet” lines The photophysical characteristics of the associated luminescence (excitation/emission) spectra. indicate strong Interaction between the excited P state Na atom and the rare gases (Ar, Kr, and Xe) used as host solids. This system is, reinvestigated with new experimental spectroscopic results and molecular dynamics (MD) calculations The so-called “violet” site in Ar and Kr has been produced by laser excitation of thermally deposited samples The simulation of the “spray-on” deposition of thin Films enables identification of tetravacancy (tv) sites of isolation for ground-state atomic sodium in Ar while in Kr this site is found in addition to single vacancy (sv) occupancy various cubic symmetry sites were taken 11110 account to simulate absorption and emission spectra using acculate Interaction potentials For the Na center dot RG diatomics. The well-known 3-fold splitting in absorption. attributed to the Jahn-Teller effect, was very well reproduced but the simulated spectra for all the sites considered ire located in the low energy region of the experimental bands The evolution of the excited state Na atom is followed revealing the nature and symmetry of the Sites that. are transiently occupied. Consistent with the large Stokes shift observed experimentally, there is an extensive rearrangement. of the lattice In the excited state with respect to the ground state. Combining all the experimental and theoretical information, in assignment of experimental violet, blue, and led absorption features is established involving single vacancy, tetravacancy, and hexavacancy sites, respectively, in Ar and Kr
|
|
Scuderi, D., Maitre, P., Rondino, F., Le Barbu-Debus, K., Lepere, V., & Zehnacker-Rentien, A. (2010). Chiral Recognition in Cinchona Alkaloid Protonated Dimers: Mass Spectrometry and UV Photodissociation Studies. JOURNAL OF PHYSICAL CHEMISTRY A, 114(9), 3306–3312.
Résumé: Chiral recognition in protonated cinchona alkaloid dimers has been studied in mass spectrometry experiments. The experimental setups involved a modified 7T FT-ICR (Fourier transform-ion cyclotron resonance) mass spectrometer (MS) and a modified Paul ion trap both equipped with an electrospray ionization source (ESI). The Paul ion trap has been coupled to a frequency-doubled dye laser. The fragmentation of protonated dimers made from cinchonidine (Cd) and the two pseudoenantiomers of quinine, namely, quinine (Qn) and quinidine (Qd), has been assessed by means of collision-induced dissociation (CID) as well as UV photodissociation (UVPD). Whereas CID fragmentation of the dimers only leads to the evaporation of the monomers, UVPD results in the additional loss of a neutral radical fragment corresponding to the quinuclidinyl radical. The effect of the excitation wavelength and of complexation with H(2)SO(4) has been studied to cast light on the reaction mechanism. Complexation with H(2)SO(4) modifies the photoreactivity of the dimers; only evaporation of the monomeric fragments, quinine, and cinchonidine is observed. Comparison between the mass spectra of the cinchona alkaloid (CdQnH(+)) or (CdQdH(+)) dimers resulting from the UVPD of (CdQnH(2)SO(4)H(+)) and that of bare (CdQnH(+)) helps propose a fragmentation mechanism, which is thought to involve fast proton transfer from the quinuclidine part of a molecular subunit to the quinoline ring. CID and UV fragmentation experiments show that the homochiral dimer is more strongly bound than the heterochiral adduct.
|
|
Turowski, M., Crepin, C., Gronowski, M., Guillemin, J. - C., Coupeaud, A., Couturier-Tamburelli, I., Pietri, N., & Kolos, R. (2010). Electronic absorption and phosphorescence of cyanodiacetylene. JOURNAL OF CHEMICAL PHYSICS, 133(7).
Résumé: Electronic absorption and emission spectra have been investigated for cyanodiacetylene, HC(5)N, an astrophysically relevant molecule. The analysis of gas-phase absorption was assisted with the parallel rare gas matrix isolation experiments and with density functional theory (DFT) predictions concerning the excited electronic states. Mid-UV systems (B) over tilde (1)Delta <-(X) over tilde (1)Sigma(+) (origin at 282.5 nm) and (A) over tilde (1)Sigma(-)<-(X) over tilde (1)Sigma(+) (306.8 nm) were observed. Vibronic assignments have been facilitated by the discovery of the visible phosphorescence a (a) over bar (3)Sigma(+) <- (X) over tilde (1)Sigma(+) in solid Ar, Kr, and Xe. Phosphorescence excitation spectra, as well as UV absorption measurements in rare gas matrices, revealed the enhancement of (A) over tilde <- (X) over tilde transitions. The vibronic structure of dispersed phosphorescence spectra supplied new data concerning the ground state bending fundamentals of matrix-isolated HC(5)N. The experimental singlet-triplet splitting, 2.92 eV in Ar, closely matches the value of 3.0 eV predicted by DFT. (C) 2010 American Institute of Physics. [doi:10.1063/1.3472978]
|
|
Actes de Conférences |
|
Crepin C., S. N., Chin W., Galaup J.P., M. C. J. G., & Arabei S.M. (2010). Absorption, fluorescence et émission stimulée de AlCl-Phtalocyanine en matrice d’Argon. In PROCEEDINGS of the International Conférence on “ Bases moléculaires, membranaires et cellulaires du fonctionnement des biosystèmes“ (157).
|
|
Chapitres de Livres |
|
K. Le Barbu-Debus. (2010). The role of deformation energy of bi-functional entities on the diastereoisomers formation. In Anne Zehnacker (Ed.), Chiral Recognition in the Gas Phase (pp. 47–59).
|
|
