Peer-reviewed Publications |
Bouchet, A., Altnoder, J., Broquier, M., & Zehnacker, A. (2014). IR-UV spectroscopy of jet-cooled 1-indanol: Restriction of the conformational space by hydration. JOURNAL OF MOLECULAR STRUCTURE, 1076, 344–351.
Résumé: The effect of hydration on a flexible amphiphilic molecule has been studied on the example of 1-hydroxyindan (1-indanol). Studies in jet-cooled conditions by means of resonance-enhanced two-photon ionization and IR-UV double resonance experiments show that the mono-hydrate 1-indanol(H2O) is formed in a dominant isomer, as well as the di-hydrate 1-indanol(H2O)(2). 1-Indanol(H2O) favors a cooperative hydrogen bond pattern with -OH center dot center dot center dot O(H)-H center dot center dot center dot pi it topology, while 1-indanol(H2O)(2) forms a cyclic hydrogen bond network with three OH center dot center dot center dot O interactions. The single conformation observed for the hydrates contrasts with the bare molecule which shows two dominant conformations, with the hydroxyl in axial or in equatorial position, respectively. Hydration therefore results in a restriction of the conformational space and conformational locking. (C) 2014 Elsevier B.V. All rights reserved.
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Capello, M. C., Broquier, M., Ishiuchi, S. I., Sohn, W. Y., Fujii, M., Dedonder-Lardeux, C., Jouvet, C., & Pino, G. A. (2014). Fast Nonradiative Decay in o-Aminophenol. Journal of Physical Chemistry A, 118, 2056–2062.
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Chaudret, R., de Courcy, B., Contreras-Garcia, J., Gloaguen, E., Zehnacker-Rentien, A., Mons, M., & Piquemal, J. P. (2014). Unraveling non-covalent interactions within flexible biomolecules: from electron density topology to gas phase spectroscopy. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 16(21), 9876–9891.
Résumé: The NCI (Non-Covalent Interactions) method, a recently-developed theoretical strategy to visualize weak non-covalent interactions from the topological analysis of the electron density and of its reduced gradient, is applied in the present paper to document intra- and inter-molecular interactions in flexible molecules and systems of biological interest in combination with IR spectroscopy. We first describe the conditions of application of the NCI method to the specific case of intramolecular interactions. Then we apply it to a series of stable conformations of isolated molecules as an interpretative technique to decipher the different physical interactions at play in these systems. Examples are chosen among neutral molecular systems exhibiting a large diversity of interactions, for which an extensive spectroscopic characterization under gas-phase isolation conditions has been obtained using state-of-the-art conformer-specific experimental techniques. The interactions presently documented range from weak intra-molecular H-bonds in simple amino-alcohols, to more complex patterns, with interactions of various strengths in model peptides, as well as in chiral bimolecular systems, where invaluable hints for the understanding of chiral recognition are revealed. We also provide a detailed technical appendix, which discusses the choices of cut-offs as well as the applicability of the NCI analysis to specific constrained systems, where local effects require attention. Finally, the NCI technique provides IR spectroscopists with an elegant visualization of the interactions that potentially impact their vibrational probes, namely the OH and NH stretching motions. This contribution illustrates the power and the conditions of use of the NCI technique, with the aim of providing an easy tool for all chemists, experimentalists and theoreticians, for the visualization and characterization of the interactions shaping complex molecular systems.
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Chin, W., Chevalier, M., Thon, R., Pollet, R., Ceponkus, J., & Crepin, C. (2014). Photochemistry of glycolaldehyde in cryogenic matrices. JOURNAL OF CHEMICAL PHYSICS, 140(22), 224319.
Résumé: The photochemistry of glycolaldehyde (GA) upon irradiation at 266 nm is investigated in argon, nitrogen, neon, and para-hydrogen matrices by IR spectroscopy. Isomerization and fragmentation processes are found to compete. The hydrogen-bonded Cis-Cis form of GA is transformed mainly to the open Trans-Trans conformer and to CO and CH3OH fragments and their mixed complexes. Different photo-induced behaviours appear depending on the matrix. In nitrogen, small amounts of Trans-Gauche and Trans-Trans conformers are detected after deposition and grow together upon irradiation. The Trans-Gauche conformer is characterized for the first time. In para-hydrogen due to a weaker cage effect additional H2CO and HCO fragments are seen. Calculations of the potential energy surfaces of S-0, S-1, and T-1 states – to analyse the torsional deformations which are involved in the isomerization process – and a kinetic analysis are presented to investigate the different relaxation pathways of GA. Fragmentation of GA under UV irradiation through the CO+CH3OH molecular channel is a minor process, as in the gas phase. (C) 2014 AIP Publishing LLC.
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Couturier-Tamburelli, I., Pietri, N., Crepin, C., Turowski, M., Guillemin, J. - C., & Kolos, R. (2014). Synthesis and spectroscopy of cyanotriacetylene (HC7N) in solid argon. Journal Of Chemical Physics, 140(4), 044329.
Résumé: UV laser irradiations of cryogenic solid argon matrices doped with a mixture of acetylene and cyanodiacetylene (HC5N) resulted in the formation of a longer carbon-nitrogen chain, cyanotriacetylene (HC7N). The identification of this species was accomplished based on IR vibrational spectroscopy (including the study of isotopically labeled compounds), on electronic luminescence spectroscopy, and on theoretical predictions. Additionally, IR absorption bands recognized as due to HC7N were detected in photolysed Ar matrices doped with a cyanoacetylene/diacetylene mixture; this assignment was confirmed with the mass spectrometry of gases released upon the warm-up of the sample. (C) 2014 AIP Publishing LLC.
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Dopfer, O., Patzer, A., Chakraborty, S., Alata, I., Omidyan, R., Broquier, M., Dedonder, C., & Jouvet, C. (2014). Electronic and vibrational spectra of protonated benzaldehyde-water clusters, BZ-(H2O)(n <= 5) H+: Evidence for ground-state proton transfer to solvent for n >= 3. Journal of Chemical Physics, 140(12), 124314.
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Feraud, G., Broquier, M., Dedonder-Lardeux, C., Gregoire, G., Soorkia, S., & Jouvet, C. (2014). Photofragmentation spectroscopy of cold protonated aromatic amines in the gas phase. Phys Chem Chem Phys, 16(11), 5250–5259.
Résumé: The electronic spectra of cold protonated aromatic amines: anilineH(+) C6H5-NH3(+), benzylamineH(+) C6H5-CH2-NH3(+) and phenylethylamineH(+) C6H5-(CH2)2-NH3(+) have been investigated experimentally in a large spectral domain and are compared to those of their hydroxyl homologues. In the low energy region, the electronic spectra are similar to their neutral analogues, which reveals the pipi* character of their first excited state. A second transition is observed from 0.4 to 1 eV above the origin band, which is assigned to the excitation of the pisigma* state. In these protonated amine molecules, there is a competition between different fragmentation channels, some being specific to UV excitation i.e., not observed in low-energy collision induced dissociation experiments. Besides, for one amine a drastic change in the fragmentation branching ratio is observed within a very short energy range that reveals the complex excited state dynamics and fragmentation processes. The experimental observations can be rationalized using a simple qualitative model, the pipi*-pisigma* model [A. L. Sobolewski, W. Domcke, C. Dedonder-Lardeux and C. Jouvet, Phys. Chem. Chem. Phys., 2002, 4, 1093-1100], which predicts that the excited state dynamics is controlled by the crossing between the pipi* excited state and a pisigma* state repulsive along the XH (X being O or N) coordinate.
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Feraud, G., Dedonder-Lardeux, C., Soorkia, S., & Jouvet, C. (2014). Photo-fragmentation spectroscopy of benzylium and 1-phenylethyl cations. J Chem Phys, 140(2), 024302.
Résumé: The electronic spectra of cold benzylium (C6H5-CH2 (+)) and 1-phenylethyl (C6H5-CH-CH3 (+)) cations have been recorded via photofragment spectroscopy. Benzylium and 1-phenylethyl cations produced from electrosprayed benzylamine and phenylethylamine solutions, respectively, were stored in a cryogenically cooled quadrupole ion trap and photodissociated by an OPO laser, scanned in parts of the UV and visible regions (600-225 nm). The electronic states and active vibrational modes of the benzylium and 1-phenylethyl cations as well as those of their tropylium or methyl tropylium isomers have been calculated with ab initio methods for comparison with the spectra observed. Sharp vibrational progressions are observed in the visible region while the absorption features are much broader in the UV. The visible spectrum of the benzylium cation is similar to that obtained in an argon tagging experiment [V. Dryza, N. Chalyavi, J. A. Sanelli, and E. J. Bieske, J. Chem. Phys. 137, 204304 (2012)], with an additional splitting assigned to Fermi resonances. The visible spectrum of the 1-phenylethyl cation also shows vibrational progressions. For both cations, the second electronic transition is observed in the UV, around 33,000 cm(-1) (4.1 eV) and shows a broadened vibrational progression. In both cases the S2 optimized geometry is non-planar. The third electronic transition observed around 40,000 cm(-1) (5.0 eV) is even broader with no apparent vibrational structures, which is indicative of either a fast non-radiative process or a very large change in geometry between the excited and the ground states. The oscillator strengths calculated for tropylium and methyl tropylium are weak. Therefore, these isomeric structures are most likely not responsible for these absorption features. Finally, the fragmentation pattern changes in the second and third electronic states: C2H2 loss becomes predominant at higher excitation energies, for both cations.
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Gloaguen, E., Brenner, V., Alauddin, M., Tardivel, B., Mons, M., Zehnacker-Rentien, A., Declerck, V., & Aitken, D. J. (2014). Direct Spectroscopic Evidence of Hyperconjugation Unveils the Conformational Landscape of Hydrazides. ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 53(50), 13756–13759.
Résumé: The stereochemistry of hydrazides makes them especially interesting as building blocks for molecular design. An exhaustive conformational analysis of three model hydrazides was conducted in a conformer-selective approach by using a combination of high-level quantum chemistry calculations and vibrational spectroscopy in the gas phase and in solution. The NH stretch frequency was found to be highly sensitive to hyperconjugation, thus making it an efficient probe of the conformation of the neighboring nitrogen atom. This property greatly assisted the identification of the isomers observed experimentally in the conformer pool. A rationalization of the hydrazide conformational landscape is proposed, therefore paving the way for a better characterization of secondary structures in larger systems.
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Henchy, C., McCaffrey, J. G., Arabei, S., Pavich, T., Galaup, J. - P., Shafizadeh, N., & Crepin, C. (2014). Free base tetraazaporphine isolated in inert gas hosts: Matrix influence on its spectroscopic and photochemical properties. JOURNAL OF CHEMICAL PHYSICS, 141(12), 124303.
Résumé: The absorption, fluorescence, and excitation spectra of free base tetraazaporphine (H(2)TAP) trapped in Ne, N-2, and Ar matrices have been recorded at cryogenic temperatures. Normal Raman spectra of H(2)TAP were recorded in KBr discs and predicted with density functional theory (DFT) using large basis sets calculations. The vibrational frequencies observed in the Raman Spectrum exhibit reasonable agreement with those deduced from the emission spectra, as well as with frequencies predicted from large basis set DFT computations. The upper state vibrational frequencies, obtained from highly resolved, site selected excitation spectra, are consistently lower than the ground state frequencies. This contrasts with the situation in free base phthalocyanine, where the upper state shows little changes in vibrational frequencies and geometry when compared with the ground state. Investigations of the photochemical properties of H(2)TAP isolated in the three matrices have been performed using the method of persistent spectral hole-burning (PSHB). This technique has been used to reveal sites corresponding to distinct N-H tautomers which were not evident in the absorption spectra. An analysis of the holes and antiholes produced with PSHB in the Q(x) (0-0) absorption band made it possible to identify inter-conversion of distinct host sites.
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Scuderi, D., Lepere, V., Piani, G., Bouchet, A., & Zehnacker-Rentien, A. (2014). Structural Characterization of the UV-Induced Fragmentation Products in an Ion Trap by Infrared Multiple Photon Dissociation Spectroscopy. JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 5(1), 56–61.
Résumé: Protonated cinchona alkaloids and their dimers undergo photochemical reaction in the gas phase, leading to UV-specific photofragments, not observed by collision-induced dissociation. Simultaneous coupling of UV and IR lasers with a Paul ion trap has been achieved for obtaining the vibrational spectrum of the fragments arising from the photodissociation. The structure of the photoproduced radical has been fully characterized by comparing the experimental spectrum to that simulated by DFT calculations.
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Shafizadeh, N., Ha-Thi, M. - H., Poisson, L., Soep, B., & Maillard, P. (2014). Observation in the gas phase of the ligation of 1-Methylimidazole to hemoprotein mimics. JOURNAL OF CHEMICAL PHYSICS, 141(17), 174310.
Résumé: Hemoprotein mimics, cobalt picket fence porphyrins have been prepared in the gas phase as neutral molecules for the first time. Their ligation properties have been studied with 1-methylimidazole and compared with those of other cobalt porphyrins, tetraphenyl porphyrin, and cobalt protoporphyrin IX chloride, in view of studying the sterical properties of the ligation. It is shown that the cobalt picket fence porphyrin can only accept one 1-methylimidazole ligand in contrast to less sterically crowded porphyrins like cobalt tetraphenylporphyrin that present two accessible ligation sites. The femtosecond dynamics of these ligated systems have been studied after excitation at 400 nm, in comparison with the unligated ones. The observed transients are formed in much shorter times, 30 fs for the ligated species, as compared to free species (100 fs), supporting the porphyrin to metal charge transfer nature of these transients. The similar decays of the ligated transients <1 ps reveal the absence of photodissociation of the cobalt-1-methylimidazole bond at this step of evolution.
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Sohn, W. Y., Ishiuchi, S., Carcabal, P., Oba, H., & Fujii, M. (2014). UV-UV hole burning and IR dip spectroscopy of homophenylalanine by laser desorption supersonic jet technique. Chemical Physics, 445, 21–30.
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Soorkia, S., Broquier, M., & Grégoire, G. (2014). Conformer- and Mode-Specific Excited State Lifetimes of Cold Protonated Tyrosine Ions. J. Phys. Chem. Lett., 5(24), 4349–4355.
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Soorkia, S., Dehon, C., Kumar, S. S., Pedrazzani, M., Frantzen, E., Lucas, B., Barat, M., Fayeton, J. A., & Jouvet, C. (2014). UV Photofragmentation Dynamics of Protonated Cystine: Disulfide Bond Rupture. J Phys Chem Lett, 5(7), 1110–1116.
Résumé: Disulfide bonds (S-S) play a central role in stabilizing the native structure of proteins against denaturation. Experimentally, identification of these linkages in peptide and protein structure characterization remains challenging. UV photodissociation (UVPD) can be a valuable tool in identifying disulfide linkages. Here, the S-S bond acts as a UV chromophore and absorption of one UV photon corresponds to a sigma-sigma* transition. We have investigated the photodissociation dynamics of protonated cystine, which is a dimer of two cysteines linked by a disulfide bridge, at 263 nm (4.7 eV) using a multicoincidence technique in which fragments coming from the same fragmentation event are detected. Two types of bond cleavages are observed corresponding to the disulfide (S-S) and adjacent C-S bond ruptures. We show that the S-S cleavage leads to three different fragment ions via three different fragmentation mechanisms. The UVPD results are compared to collision-induced dissociation (CID) and electron-induced dissociation (EID) studies.
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Zehnacker, A. (2014). Chirality effects in gas-phase spectroscopy and photophysics of molecular and ionic complexes: contribution of low and room temperature studies. INTERNATIONAL REVIEWS IN PHYSICAL CHEMISTRY, 33(2), 151–207.
Résumé: This review focuses on chirality effects in spectroscopy and photophysics of chiral molecules or protonated ions, and their weakly bound complexes, isolated in the gas phase. Low-temperature studies in jet-cooled conditions allow disentangling the different interactions at play and shed light on the ancillary interactions responsible for chiral recognition, like OH...pi or CH...pi, which would be blurred at room temperature. The consequences of these interactions on chiral recognition in condensed phase are described, as well as the influence of higher energy conformers, which can be accessed in room-temperature experiments. The role of kinetic effects and solvation in jet-cooled experiments is discussed. Last, examples of dramatic chirality effects in photo-induced dissociation are given.
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