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Accueil > Équipes scientifiques > Structure et dynamique des systèmes complexes isolés photoexcités (SYSIPHE) > CHIralité et spectroscoPIE (CHIPIE) > Chirality and photostability of quinine derivatives

Chirality and photostability of quinine derivatives

par Zehnacker-Rentien Anne - 4 novembre 2015 (modifié le 28 septembre 2018)

This work aims at understanding the photodissociation mechanisms and the role of stereochemical factors in the photostability of complex alkaloid molecules. Please see our posters

Protonated cinchona alkaloids and their dimers are formed in an ion trap and studied by photodissociation either in the IR range (IRMPD) or in the UV range, in collaboration withe Debora Scuderi Laboratoire de chimie physique - Orsay.

The studied dimers contain a quinine unit as well as one of the psudoenantiomers iLes dimères étudiés contiennent une molécule de quinine et un, namely, cinchonine or cinchonidine. One can thereby study the homochiral dimer (quinine-cinchonidine) and the heterochiral dimer (quinine-cinchonine)

They have been spectroscopically characterised in the IR range. Their collision-induced dissociation leads to the evaporation of the monomers and shows important chirality effects. The dissociation yield is smaller for the homochiral complex. The photo-fragmentation induced by a UV laser leads to the following products.

The proposed mechanism have been recently confirmed by experiments coupling simultanously UV and Free-electron IR lasers in the ion trap. The UV induces photofragmentation while the IR probes the structure of the products. The two photoproducts have been characterised by their vibrational spectra. In particular, an exoic protonated species with the proton located in the quinoline nitrogen has been shown to be formed by ESIPT (Excited State Proton Transfer)

Combining the structural characterisation of the fragments with quantum chemical calculations, we are able to propose a photofragmentation mechanism which involves two paths :
Excitation ot the protonated moiety of the dimer leads to coupling with a dissociative pi-sigma* state leading to hydrogen transfer combined to electron transfer, acompanied by the cleavage of the adjacent CC cleavage.
Excitation of the neutral moiety leads to ESIPT followed by dissociation of the intermolecular bond.

Spectre vibrationnel du produit de photodissociation du dimère de la quinine

In parallel, we have studied jet-cooled neutral quinine by means of IR-UV double resonance spectroscopy. The molecules are put intact in the gas phase thanks to a laser ablation source (picture in Techniques et Développements expérimentaux)


Photofragmentation mechanisms in protonated chiral cinchona alkaloids
Kumar, Sunil ; Lucas, Bruno ; Fayeton, Jacqueline ; Scuderi, Debora ; Alata, Ivan ; Broquier, Michel ; Barbu-Debus, Katia Le ; Lepère, Valeria ; Zehnacker, Anne
Phys. Chem. Chem. Phys., 2016,18, 22668-22677

Exotic Protonated Species Produced by UV-Induced Photofragmentation of a Protonated Dimer : Metastable Protonated Cinchonidine
Ivan Alata, Debora Scuderi, Valeria Lepere, Vincent Steinmetz, Fabrice Gobert, Loïc Thiao-Layel, Katia Le Barbu-Debus, and Anne Zehnacker-Rentien
J. Phys. Chem. A, 2015, 119 (39), pp 10007–10015

Chirality effects in gas-phase spectroscopy and photophysics of molecular and ionic complexes : contribution of low and room temperature studies
A Zehnacker
International Reviews in Physical Chemistry (2014) 33 (2), 151-207

Structural Characterization of the UV-Induced Fragmentation Products in an Ion Trap by Infrared Multiple Photon Dissociation Spectroscopy
D Scuderi, V Lepere, G Piani, A Bouchet, A Zehnacker-Rentien
The Journal of Physical Chemistry Letters (2013) 5 (1), 56-61

Chiral Recognition in Cinchona Alkaloid Protonated Dimers : Mass Spectrometry and UV Photodissociation
D. Scuderi, P. Maitre, F. Rondino, K. Le Barbu-Debus, V. Lepere and A. Zehnacker-Rentien
J. Phys. Chem. A, 2010, 114 (9), 3306–3312