Peer-reviewed Publications |
Alata, I., Omidyan, R., Dedonder-Lardeux, C., Broquier, M., & Jouvet, C. (2009). Electronically excited states of protonated aromatic molecules: benzaldehyde. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 11(48), 11479–11486.
Résumé: The photofragmentation spectrum of protonated benzaldehyde has been recorded in the 435-385 nm wavelength range. The first excited state is a pi pi* state, strongly red shifted compared to the pi pi* state of neutral benzaldehyde. The spectrum presents well resolved vibronic bands in contrast to some other protonated aromatic molecules like benzene or tryptophan in which the excited state dynamics is so fast that no vibrational structure can be observed. The bands can be assigned on the basis of a Franck-Condon analysis using ground and excited state frequencies calculated at the CC2/TZVP level.
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Carrera, A., Nielsen, I. B., Carcabal, P., Dedonder, C., Broquier, M., Jouvet, C., Domcke, W., & Sobolewski, A. L. (2009). Biradicalic excited states of zwitterionic phenol-ammonia clusters. J. Chem. Phys., 130(2), 024302.
Résumé: Phenol-ammonia clusters with more than five ammonia molecules are proton transferred species in the ground state. In the present work, the excited states of these zwitterionic clusters have been studied experimentally with two-color pump probe methods on the nanosecond time scale and by ab initio electronic-structure calculations. The experiments reveal the existence of a long-lived excited electronic state with a lifetime in the 50-100 ns range, much longer than the excited state lifetime of bare phenol and small clusters of phenol with ammonia. The ab initio calculations indicate that this long-lived excited state corresponds to a biradicalic system, consisting of a phenoxy radical that is hydrogen bonded to a hydrogenated ammonia cluster. The biradical is formed from the locally excited state of the phenolate anion via an electron transfer process, which neutralizes the charge separation of the ground state zwitterion.
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Chakraborty, S., Omidyan, R., Alata, I., Nielsen, I. B., Dedonder, C., Broquier, M., & Jouvet, C. (2009). Protonated Benzene Dimer: An Experimental and Ab Initio Study. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 131(31), 11091–11097.
Résumé: The excitation spectrum of the protonated benzene dimer has been recorded in the 415-600 nm wavelength range. In contrast to the neutral iso-electronic benzene dimer, its absorption spectrum extends in the visible spectral region. This huge spectral shift has been interpreted with ab initio calculations, which indicate that the first excited states should be charge transfer states.
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Grégoire, G., Lucas, B., Barat, M., Fayeton, J. A., Dedonder-Lardeux, C., & Jouvet, C. (2009). UV photoinduced dynamics in protonated aromatic amino acid. Eur. Phys. J. D, 51(1), 109–116.
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Kadhane, U., Pérot, M., Lucas, B., Barat, M., Fayeton, J. A., Jouvet, C., Ehlerding, A., Kirketerp, M. - B. S., Nielsen, S. B., Wyer, J. A., & Zettergren, H. (2009). Photodissociation of protonated tryptamine and its supramolecular complex with 18-crown-6 ether: Dissociation times and channels, absorption spectra, and excited states calculations. Chemical Physics Letters, 480(1-3), 57–61.
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Le Barbu-Debus, K., Broquier, M., Mahjoub, A., & Zehnacker-Rentien, A. (2009). Chiral recognition in jet-cooled complexes of (1R,2S)-(+)-cis-1-amino-2-indanol and methyl lactate: on the importance of the CH...pi interaction. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 11(35), 7589–7598.
Résumé: Complexation between (1R,2S)-(+)-cis-1-amino-2-indanol (AI) and the two enantiomers of methyl lactate has been studied by means of laser-induced fluorescence, resonance-enhanced two-photon ionisation, and IR-UV double resonance spectroscopy, in the region of 3 μm. Two isomeric complexes have been spectroscopically characterised for each diastereoisomer. Comparison with ab initio calculations shows that the most stable form is an insertion structure, common to the two diastereoisomers, in which the OH group of methyl lactate inserts into the intramolecular bond of AI. This structure shows almost no chiral discrimination. A secondary structure has been observed, which is specific to each enantiomer. It involves a main hydrogen bond from the OH group of methyl lactate to AI together with weaker hydrogen bonds, which depend on chirality. The enantioselectivity in the hydrogen bond topology is due to a weak stabilizing CH center dot center dot center dot pi interaction, involving the CH located on the asymmetric carbon of methyl lactate, which can be obtained for one of the enantiomers only.
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Lepere, V., Picard, Y. J., Barat, M., Fayeton, J. A., Lucas, B., & Beroff, K. (2009). Photodissociation dynamics of Ar2(+) and Ar3(+) excited by 527 nm photons. J Chem Phys, 130(19), 194301.
Résumé: The photofragmentation dynamics of Ar(2)(+) and Ar(3)(+) clusters has been investigated at a 527 nm wavelength (2.35 eV) using a setup that allows simultaneous detection of the ionic and neutral fragments in a coincidence experiment. Measurement of positions and times of flight enables in principle a complete description of the fragmentation dynamics. The photofragmentation dynamics of Ar(3)(+) clusters is similar to that of Ar(2)(+) with, in addition, the ejection of a third fragment that can be neutral or ionized via a resonant electron capture. This is attributed to the triangular geometry of the Ar(3)(+) ion.
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Mahjoub, A., Chakraborty, A., Lepere, V., Le Barbu-Debus, K., Guchhait, N., & Zehnacker, A. (2009). Chirality-dependent hydrogen bond direction in jet-cooled (S)-1,2,3,4-tetrahydro-3-isoquinoline methanol (THIQM): IR-ion dip vibrational spectroscopy of the neutral and the ion. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 11(25), 5160–5169.
Résumé: The structural modifications of (S)-1,2,3,4-tetrahydro-3-isoquinoline methanol (THIQM) upon ionisation have been investigated in jet-cooled conditions, by means of laser-induced fluorescence, REMPI, and IR-UV ion-dip spectroscopy of the neutral ground state and the ion. These results combined with ab initio calculations, support the presence in the jet of two low-energy conformers of THIQM. In the most stable Conformer I, the CH(2)OH substituent acts as a hydrogen bond donor to the nitrogen lone pair in the equatorial position. In this case, the nitrogen atom is in ( S) configuration. Conformer II shows the opposite NH center dot center dot center dot O hydrogen bond from the hydrogen atom in the equatorial position of nitrogen to the OH group. In this case, the nitrogen atom is in ( R) configuration. This chirality dependence of the hydrogen bond direction is lost upon ionisation. While ionisation of Conformer II reinforces the NH center dot center dot center dot O hydrogen bond, ionisation of Conformer I induces its isomerisation to the same ion as Conformer II, i.e. a change in hydrogen bond direction.
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